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283 results on '"Sadun, A. C."'

1. A multi-wavelength study to decipher the 2017 flare of the blazar OJ 287

Author: Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Brill, A., Caldwell, J. P., Carini, M., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Foote, J., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W., Hanna, D., Hervet, O., Hinrichs, C. E., Hoang, J., Holder, J., Humensky, T. B., Jin, W., Johnson, M. N., Kaaret, P., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K., Korzoun, N., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., EMcGrath, C., Millard, M. J., Millis, J., Mooney, C. L., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Pohl, M., Pueschel, E., Quinn, J., Rabinowitz, P. L., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Sadun, A. C., Saha, L., Santander, M., Sembroski, G. H., Shahinyan, K., Shang, R., Splettstoesser, M., Tak, D., Talluri, A. K., Tucci, J. V., Williams, D. A., Wong, S. L., Jorstad, S. G., Lico, R., Lusen, P., and Marscher, A. P.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $\gamma$-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of $10\sigma$ (from 2016 December 9 to 2017 March 31). The time-averaged VHE $\gamma$-ray spectrum was consistent with a soft power law ($\Gamma = -3.81 \pm 0.26$) and an integral flux corresponding to $\sim2.4\%$ that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal complex flaring behavior, primarily in the soft X-ray and VHE bands. To investigate the possible origin of such an event, our study focuses on three distinct activity states: before, during, and after the February 2017 peak. The spectral energy distributions during these periods suggest the presence of at least two non-thermal emission zones, with the more compact one responsible for the observed flare. Broadband modeling results and observations of a new radio knot in the jet of OJ~287 in 2017 are consistent with a flare originating from a strong recollimation shock outside the radio core., Comment: 21 pages, 7 figures, accepted for publication in The Astrophysical Journal
Published: 2024

2. The variability patterns of the TeV blazar PG 1553+113 from a decade of MAGIC and multi-band observations

Author: MAGIC Collaboration, Abe, H., Abe, S., Abhir, J., Acciari, V. A., Agudo, I., Aniello, T., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Arcaro, C., Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., de Almeida, U. Barres, Batković, I., Baxter, J., González, J. Becerra, Bernardini, E., Bernete, J., Berti, A., Besenrieder, J., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bošnjak, Ž., Burelli, I., Busetto, G., Campoy-Ordaz, A., Carosi, A., Carosi, R., Carretero-Castrillo, M., Castro-Tirado, A. J., Chai, Y., Cifuentes, A., Cikota, S., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Del Popolo, A., Delfino, M., Delgado, J., Mendez, C. Delgado, Depaoli, D., Di Pierro, F., Di Venere, L., Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Emery, G., Escudero, J., Fariña, L., Fattorini, A., Foffano, L., Font, L., Fukami, S., Fukazawa, Y., López, R. J. García, Gasparyan, S., Gaug, M., Paiva, J. G. Giesbrecht, Giglietto, N., Giordano, F., Gliwny, P., Grau, R., Green, J. G., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hovatta, T., Hrupec, D., Hütten, M., Imazawa, R., Inada, T., Iotov, R., Ishio, K., Martínez, I. Jiménez, Jormanainen, J., Kerszberg, D., Kluge, G. W., Kobayashi, Y., Kouch, P. M., Kubo, H., Kushida, J., Lezáun, M. Láinez, Lamastra, A., Leone, F., Lindfors, E., Liodakis, I., Lombardi, S., Longo, F., López-Moya, M., López-Oramas, A., Loporchio, S., Lorini, A., Fraga, B. Machado de Oliveira, Majumdar, P., Makariev, M., Maneva, G., Mang, N., Manganaro, M., Mannheim, K., Mariotti, M., Martínez, M., Martínez-Chicharro, M., Mas-Aguilar, A., Mazin, D., Menchiari, S., Mender, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., González, M. Molero, Molina, E., Mondal, H. A., Moralejo, A., Morcuende, D., Nakamori, T., Nanci, C., Neustroev, V., Nigro, C., Nikolić, L., Nilsson, K., Nishijima, K., Ekoume, T. Njoh, Noda, K., Nozaki, S., Ohtani, Y., Okumura, A., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavlović, D., Persic, M., Pihet, M., Pirola, G., Podobnik, F., Moroni, P. G. Prada, Prandini, E., Principe, G., Priyadarshi, C., Rhode, W., Ribó, M., Rico, J., Righi, C., Sahakyan, N., Saito, T., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schmuckermaier, F., Schubert, J. L., Schweizer, T., Sciaccaluga, A., Sitarek, J., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Suda, Y., Suutarinen, S., Tajima, H., Takeishi, R., Tavecchio, F., Temnikov, P., Terauchi, K., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Ventura, S., Verguilov, V., Viale, I., Vigorito, C. F., Vitale, V., Walter, R., Wunderlich, C., Yamamoto, T., collaborators, MWL, Jermak, H., Steele, I. A., Smith, P. S., Blinov, D., Raiteri, C. M., Villata, M., Mirzaqulov, D. O., Kurtanidze, S. O., Carosati, D., Savchenko, S. S., Acosta-Pulido, J. A., Borman, G. A., Bozhilov, V., Carnerero, M. I., Chigladze, R. A., Damljanovic, G., Ehgamberdiev, S. A., Feige, M., Grishina, T. S., Gupta, A. C., Hagen-Thorn, V. A., Ibryamov, S., Ivanidze, R. Z., Jorstad, S. G., Kania, J., Kimeridze, G. N., Kopatskaya, E. N., Kopp, M., Kunkel, L., Kurtanidze, O. M., Larionov, V. M., Larionova, E. G., Larionova, L. V., Lorey, C., Marchini, A., Marscher, A. P., Minev, M., Morozova, D. A., Nikolashvili, M. G., Ovcharov, E., Reinhart, D., Sadun, A. C., Scherbantin, A., Schneider, L., Semkov, E., Sigua, L. A., Steineke, R., Troitskaya, Yu. V., Troitskiy, I. S., Valcheva, A., Vasilyev, A. A., Vince, O., Zaharieva, E., Zottmann, N., Kiehlmann, S., Readhead, A., Max-Moerbeck, W., Reeves, R. A., Sandrinelli, A., Ramazani, V. Fallah, Giroletti, M., Righini, S., Marchili, N., Patricelli, B., Ghirlanda, G., and Lico, R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: PG 1553+113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high-energy (VHE; >100 GeV) gamma-ray emitter. To better understand its properties and identify the underlying physical processes driving its variability, the MAGIC Collaboration initiated a multiyear, multiwavelength monitoring campaign in 2015 involving the OVRO 40-m and Medicina radio telescopes, REM, KVA, and the MAGIC telescopes, Swift and Fermi satellites, and the WEBT network. The analysis presented in this paper uses data until 2017 and focuses on the characterization of the variability. The gamma-ray data show a (hint of a) periodic signal compatible with literature, but the X-ray and VHE gamma-ray data do not show statistical evidence for a periodic signal. In other bands, the data are compatible with the gamma-ray period, but with a relatively high p-value. The complex connection between the low and high-energy emission and the non-monochromatic modulation and changes in flux suggests that a simple one-zone model is unable to explain all the variability. Instead, a model including a periodic component along with multiple emission zones is required., Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society. 19 pages, 9 figures. Corresponding authors: Elisa Prandini, Antonio Stamerra, Talvikki Hovatta
Published: 2024
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3. Investigating Possible Correlations between Gamma-Ray and Optical Lightcurves for TeV-Detected Northern Blazars over 8 Years of Observations

Author: Acharyya, Atreya and Sadun, Alberto C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: Blazars are a subclass of active galactic nuclei (AGN) having relativistic jets aligned within a few degrees of our line-of-sight and form the majority of the AGN detected in the TeV regime. The Fermi-Large Area Telescope (LAT) is a pair-conversion telescope, sensitive to photons having energies between 20 MeV and 2 TeV, and is capable of scanning the entire gamma-ray sky every three hours. Despite the remarkable success of the Fermi mission, many questions still remain unanswered, such as the site of gamma-ray production and the emission mechanisms involved. The Asteroid Terrestrial-impact Last Alert System (ATLAS) is a high cadence all sky survey system optimized to be efficient for finding potentially dangerous asteroids, as well as in tracking and searching for highly variable and transient sources, such as AGN. In this study, we investigate possible correlations between the Fermi-LAT observations in the 100 MeV-300 GeV energy band and the ATLAS optical data in the R-band, centered at 679 nm, for a sample of 18 TeV-detected northern blazars over 8 years of observations between 2015 and 2022. Under the assumption that the optical and gamma-ray flares are produced by the same outburst propagating down the jet, the strong correlations found for some sources suggest a single-zone leptonic model of emission., Comment: 11 pages, 5 figures, Accepted in Galaxies. arXiv admin note: text overlap with arXiv:2305.02860
Published: 2023
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4. Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A

Author: Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Brill, A., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W., Hanna, D., Hervet, O., Hinrichs, C. E., Hoang, J., Holder, J., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K., Korzoun, N., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Millard, M. J., Millis, J., Mooney, C. L., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Sadeh, I., Sadun, A. C., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Talluri, A. Kaushik, Tucci, J. V., Vassiliev, V. V., Weinstein, A., Williams, D. A., Wong, S. L., Woo, J., Aharonian, F., Aschersleben, J., Backes, M., Martins, V. Barbosa, Batzofin, R., Becherini, Y., Berge, D., Bernlohr, K., Bi, B., Bottcher, M., Boisson, C., Bolmont, J., de Lavergne, M. de Bony, Borowska, J., Bouyahiaoui, M., Bradascio, F., Breuhaus, M., Brose, R., Brun, F., Bruno, B., Bulik, T., Burger-Scheidlin, C., Caroff, S., Casanova, S., Cecil, R., Celic, J., Cerruti, M., Chand, T., Chandra, S., Chen, A., Chibueze, J., Chibueze, O., Cotter, G., Dai, S., Mbarubucyeye, J. Damascene, Djannati-Atai, A., Dmytriiev, A., Doroshenko, V., Einecke, S., Ernenwein, J. -P., de Clairfontaine, G. Fichet, Filipovic, M., Fontaine, G., Fussling, M., Funk, S., Gabici, S., Ghafourizadeh, S., Giavitto, G., Glawion, D., Glicenstein, J. F., Goswami, P., Grolleron, G., Haerer, L., Hinton, J. A., Holch, T. L., Holler, M., Horns, D., Jamrozy, M., Jankowsky, F., Joshi, V., Jung-Richardt, I., Kasai, E., Katarzynski, K., Khatoon, R., Khelifi, B., Klepser, S., Kluzniak, W., Kosack, K., Kostunin, D., Lang, R. G., Stum, S. Le, Lemiere, A., Lenain, J. P., Leuschner, F., Lohse, T., Luashvili, A., Lypova, I., Mackey, J., Malyshev, D., Marandon, V., Marchegiani, P., Marcowith, A., Marti-Devesa, G., Marx, R., Mitchell, A., Moderski, R., Mohrmann, L., Montanari, A., Moulin, E., Murach, T., Nakashima, K., Niemiec, J., Noel, A. Priyana, O'Brien, P., Olivera-Nieto, L., Wilhelmi, E. de Ona, Ostrowski, M., Panny, S., Panter, M., Peron, G., Prokhorov, D. A., Puhlhofer, G., Punch, M., Quirrenbach, A., Reichherzer, P., Reimer, A., Reimer, O., Ren, H., Renaud, M., Rieger, F., Rudak, B., Ruiz-Velasco, E., Sahakian, V., Santangelo, A., Sasaki, M., Schafer, J., Schussler, F., Schutte, H. M., Schwanke, U., Shapopi, J. N. S., Specovius, A., Spencer, S., Stawarz, L., Steenkamp, R., Steinmassl, S., Sushch, I., Suzuki, H., Takahashi, T., Tanaka, T., Terrier, R., van Eldik, C., Vecchi, M., Veh, J., Venter, C., Vink, J., White, R., Wierzcholska, A., Wong, Yu Wun, Zacharias, M., Zargaryan, D., Zdziarski, A. A., Zech, A., Zouari, S., Zywucka, N., and Mori, K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.2$^\circ$ away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on December 8, 2021. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV gamma-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ray flux. The X-ray data from Swift-XRT and NuSTAR characterize the transition between the low-energy and high-energy components of the broadband spectral energy distribution (SED), and the gamma-ray data from Fermi -LAT, VERITAS, and H.E.S.S. require a spectral cut-off near 100 GeV. Both X-ray and gamma-ray measurements provide strong constraints on the leptonic and hadronic models. We analytically explore a synchrotron self-Compton model, an external Compton model, and a lepto-hadronic model. Models that are entirely based on internal photon fields face serious difficulties in matching the observed SED. The existence of an external photon field in the source would instead explain the observed gamma-ray spectral cut-off in both leptonic and lepto-hadronic models and allow a proton jet power that marginally agrees with the Eddington limit in the lepto-hadronic model. We show a numerical lepto-hadronic model with external target photons that reproduces the observed SED and is reasonably consistent with the neutrino event despite requiring a high jet power., Comment: 21 pages, 3 figures, accepted by ApJ
Published: 2023

5. Multi-messenger characterization of Mrk 501 during historically low X-ray and $\gamma$-ray activity

Author: MAGIC collaboration, Abe, H., Abe, S., Acciari, V. A., Agudo, I., Aniello, T., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Arcaro, C., Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., de Almeida, U. Barres, Barrio, J. A., Batković, I., Baxter, J., González, J. Becerra, Bednarek, W., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bošnjak, Ž., Burelli, I., Busetto, G., Carosi, R., Carretero-Castrillo, M., Castro-Tirado, A. J., Ceribella, G., Chai, Y., Chilingarian, A., Cikota, S., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Del Popolo, A., Delfino, M., Delgado, J., Mendez, C. Delgado, Depaoli, D., Di Pierro, F., Di Venere, L., Espiñeira, E. Do Souto, Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Emery, G., Escudero, J., Ramazani, V. Fallah, Fariña, L., Fattorini, A., Foffano, L., Font, L., Fruck, C., Fukami, S., Fukazawa, Y., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Paiva, J. G. Giesbrecht, Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Grau, R., Green, D., Green, J. G., Hadasch, D., Hahn, A., Hassan, T., Heckmann, L., Herrera, J., Hrupec, D., Hütten, M., Imazawa, R., Inada, T., Iotov, R., Ishio, K., Martínez, I. Jiménez, Jormanainen, J., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Linhoff, L., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Lorini, A., Lyard, E., Fraga, B. Machado de Oliveira, Majumdar, P., Makariev, M., Maneva, G., Mang, N., Manganaro, M., Mangano, S., Mannheim, K., Mariotti, M., Martínez, M., Mas-Aguilar, A., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., Molina, E., Mondal, H. A., Moralejo, A., Morcuende, D., Moreno, V., Nakamori, T., Nanci, C., Nava, L., Neustroev, V., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Nishijima, K., Ekoume, T. Njoh, Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Okumura, A., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Persic, M., Pihet, M., Pirola, G., Podobnik, F., Moroni, P. G. Prada, Prandini, E., Principe, G., Priyadarshi, C., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schmuckermaier, F., Schubert, J. L., Schweizer, T., Sitarek, J., Sliusar, V., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Surić, T., Tajima, H., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terauchi, K., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Acosta, M. Vazquez, Ventura, S., Verguilov, V., Viale, I., Vigorito, C. F., Vitale, V., Vovk, I., Walter, R., Will, M., Wunderlich, C., Yamamoto, T., Zarić, D., groups, Other, collaborations, Cerruti, M., Acosta-Pulido, J. A., Apolonio, G., Bachev, R., Baloković, M., Benítez, E., Björklund, I., Bozhilov, V., Brown, L. F., Bugg, A., Carbonell, W., Carnerero, M. I., Carosati, D., Casadio, C., Chamani, W., Chen, W. P., Chigladze, R. A., Damljanovic, G., Epps, K., Erkenov, A., Feige, M., Finke, J., Fuentes, A., Gazeas, K., Giroletti, M., Grishina, T. S., Gupta, A. C., Gurwell, M. A., Heidemann, E., Hiriart, D., Hou, W. J., Hovatta, T., Ibryamov, S., Joner, M. D., Jorstad, S. G., Kania, J., Kiehlmann, S., Kimeridze, G. N., Kopatskaya, E. N., Kopp, M., Korte, M., Kotas, B., Koyama, S., Kramer, J. A., Kunkel, L., Kurtanidze, S. O., Kurtanidze, O. M., Lähteenmäki, A., López, J. M., Larionov, V. M., Larionova, E. G., Larionova, L. V., Leto, C., Lorey, C., Mújica, R., Madejski, G. M., Marchili, N., Marscher, A. P., Minev, M., Modaressi, A., Morozova, D. A., Mufakharov, T., Myserlis, I., Nikiforova, A. A., Nikolashvili, M. G., Ovcharov, E., Perri, M., Raiteri, C. M., Readhead, A. C. S., Reimer, A., Reinhart, D., Righini, S., Rosenlehner, K., Sadun, A. C., Savchenko, S. S., Scherbantin, A., Schneider, L., Schoch, K., Seifert, D., Semkov, E., Sigua, L. A., Singh, C., Sola, P., Sotnikova, Y., Spencer, M., Steineke, R., Stojanovic, M., Strigachev, A., Tornikoski, M., Traianou, E., Tramacere, A., Troitskaya, Yu. V., Troitskiy, I. S., Trump, J. B., Tsai, A., Valcheva, A., Vasilyev, A. A., Verrecchia, F., Villata, M., Vince, O., Vrontaki, K., Weaver, Z. R., Zaharieva, E., and Zottmann, N.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We study the broadband emission of Mrk 501 using multi-wavelength observations from 2017 to 2020 performed with a multitude of instruments, involving, among others, MAGIC, Fermi-LAT, NuSTAR, Swift, GASP-WEBT, and OVRO. Mrk 501 showed an extremely low broadband activity, which may help to unravel its baseline emission. Nonetheless, significant flux variations are detected at all wavebands, with the highest occurring at X-rays and very-high-energy (VHE) $\gamma$-rays. A significant correlation ($>$3$\sigma$) between X-rays and VHE $\gamma$-rays is measured, supporting leptonic scenarios to explain the variable parts of the emission, also during low activity. This is further supported when we extend our data from 2008 to 2020, and identify, for the first time, significant correlations between Swift-XRT and Fermi-LAT. We additionally find correlations between high-energy $\gamma$-rays and radio, with the radio lagging by more than 100 days, placing the $\gamma$-ray emission zone upstream of the radio-bright regions in the jet. Furthermore, Mrk 501 showed a historically low activity in X-rays and VHE $\gamma$-rays from mid-2017 to mid-2019 with a stable VHE flux ($>$0.2 TeV) of 5% the emission of the Crab Nebula. The broadband spectral energy distribution (SED) of this 2-year-long low-state, the potential baseline emission of Mrk 501, can be characterized with one-zone leptonic models, and with (lepto)-hadronic models fulfilling neutrino flux constraints from IceCube. We explore the time evolution of the SED towards the low-state, revealing that the stable baseline emission may be ascribed to a standing shock, and the variable emission to an additional expanding or traveling shock., Comment: 55 pages, 30 figures, 14 tables, accepted by APJS. Corresponding authors are L. Heckmann, D. Paneque, S. Gasparyan, M. Cerruti, and N. Sahakyan
Published: 2022
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6. Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017

Author: MAGIC Collaboration, Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Artero, M., Asano, K., Babić, A., Baquero, A., de Almeida, U. Barres, Barrio, J. A., Batković, I., González, J. Becerra, Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Blanch, O., Bošnjak, Ž., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Mendez, C. Delgado, Depaoli, D., Di Pierro, F., Di Venere, L., Espiñeira, E. Do Souto, Prester, D. Dominis, Donini, A., Doro, M., Ramazani, V. Fallah, Fattorini, A., Ferrara, G., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jiménez, I., Jormanainen, J., Jouvin, L., Kajiwara, Y., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Fraga, B. Machado de Oliveira, Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Neustroev, V., Nigro, C., Nilsson, K., Nishijima, K., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Peñil, P., Perennes, C., Persic, M., Moroni, P. G. Prada, Prandini, E., Priyadarshi, C., Puljak, I., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schmidt, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Spolon, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Surić, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Wunderlich, C., Zarić, D., Collaboration, FACT, Baack, D., Balbo, M., Biederbeck, N., Biland, A., Bretz, T., Buss, J., Dorner, D., Eisenberger, L., Elsaesser, D., Hildebrand, D., Iotov, R., Mannheim, K., Neise, D., Noethe, M., Paravac, A., Rhode, W., Schleicher, B., Sliusar, V., Walter, R., groups, Other, collaborations, D'Ammando, F., Horan, D., Lien, A. Y., Baloković, M., Madejski, G. M., Perri, M., Verrecchia, F., Leto, C., Lähteenmäki, A., Tornikoski, M., Ramakrishnan, V., Järvelä, E., Vera, R. J. C., Villata, M., Raiteri, C. M., Gupta, A. C., Pandey, A., Fuentes, A., Agudo, I., Casadio, C., Semkov, E., Ibryamov, S., Marchini, A., Bachev, R., Strigachev, A., Ovcharov, E., Bozhilov, V., Valcheva, A., Zaharieva, E., Damljanovic, G., Vince, O., Larionov, V. M., Borman, G. A., Grishina, T. S., Hagen-Thorn, V. A., Kopatskaya, E. N., Larionova, E. G., Larionova, L. V., Morozova, D. A., Nikiforova, A. A., Savchenko, S. S., Troitskiy, I. S., Troitskaya, Y. V., Vasilyev, A. A., Merkulova, O. A., Chen, W. P., Samal, M., Lin, H. C., Moody, J. W., Sadun, A. C., Jorstad, S. G., Marscher, A. P., Weaver, Z. R., Feige, M., Kania, J., Kopp, M., Kunkel, L., Reinhart, D., Scherbantin, A., Schneider, L., Lorey, C., Acosta-Pulido, J. A., Carnerero, M. I., Carosati, D., Kurtanidze, S. O., Kurtanidze, O. M., Nikolashvili, M. G., Chanishvili, R. G., Chigladze, R. A., Ivanidze, R. Z., Kimeridze, G. N., Sigua, L. A., Joner, M. D., Spencer, M., Giroletti, M., Marchili, N., Righini, S., Rizzi, N., and Bonnoli, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with special focus on the multi-band flux correlations. The dataset has been collected through an extensive multiwavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina and Mets\"ahovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components. The very-high-energy (VHE; E > 100 GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance during a few days without a simultaneous increase in the X-ray flux (i.e. orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. Our multi-band correlation study also hints at an anti-correlation between UV/optical and X-ray at a significance higher than 3 sigmas. A VHE flare observed on 2017 February 4 shows gamma-ray variability on multi-hour timescales, with a factor 10 increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors., Comment: 38 pages, 23 figures, accepted for publication in Astronomy and Astrophysics. Corresponding authors: Axel Arbet-Engels, David Paneque
Published: 2021
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7. Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and $\gamma$-ray activity in 2015$-$2016

Author: MAGIC Collaboration, Acciari, V. A., Ansoldi, S., Antonelli, L. A., Asano, K., Babić, A., Banerjee, B., Baquero, A., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Blanch, O., Bonnoli, G., Bošnjak, Ž., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Mendez, C. Delgado, Depaoli, D., Di Girolamo, T., Di Pierro, F., Di Venere, L., Espiñeira, E. Do Souto, Prester, D. Dominis, Donini, A., Doro, M., Ramazani, V. Fallah, Fattorini, A., Ferrara, G., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jormanainen, J., Jouvin, L., Kajiwara, Y., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Loporchio, S., Fraga, B. Machado de Oliveira, Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Mender, S., Mićanović, S., Miceli, D., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Peñil, P., Perennes, C., Persic, M., Moroni, P. G. Prada, Prandini, E., Priyadarshi, C., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Spolon, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Surić, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Tosti, L., Truzzi, S., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Zarić, D., collaboration, FACT, Arbet-Engels, A., Baack, D., Balbo, M., Beck, M., Biederbeck, N., Biland, A., Bretz, T., Bruegge, K., Buss, J., Dorner, D., Elsaesser, D., Hildebrand, D., Iotov, R., Klinger, M., Mannheim, K., Neise, D., Neronov, A., Noethe, M., Paravac, A., Sliusar, V., Theissen, F., Walter, R., Collaborators, MWL, Valverde, J., Horan, D., Giroletti, M., Perri, M., Verrecchia, F., Leto, C., Sadun, A. C., Moody, J. W., Joner, M., Marscher, A. P., Jorstad, S. G., Lähteenmäki, A., Tornikoski, M., Ramakrishnan, V., Järvelä, E., Vera, R. J. C., Righini, S., and Lien, A. Y.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report a characterization of the multi-band flux variability and correlations of the nearby (z=0.031) blazar Markarian 421 (Mrk 421) using data from Mets\"{a}hovi, Swift, Fermi-LAT, MAGIC, FACT and other collaborations and instruments from November 2014 till June 2016. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F$_{>1\mathrm{TeV}}<$ 1.7$\times$10$^{-12}$ ph cm$^{-2}$ s$^{-1}$) and in the 2-10 keV (X-ray) band (F$_{2-10 \mathrm{keV}}<$3.6$\times$10$^{-11}$ erg cm$^{-2}$ s$^{-1}$), during which the Swift-BAT data suggests an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very-high-energy (E$>$0.1 TeV) $\gamma$-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HR$_\mathrm{keV}$ and HR$_\mathrm{TeV}$ show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 days centered at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 days centered at a time lag of $43^{+9}_{-6}$ days.This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a LogNormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process., Comment: 45 pages, 30 figures, 6 tables, accepted for publication in MNRAS
Published: 2020
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8. The Great Markarian 421 Flare of February 2010: Multiwavelength variability and correlation studies

Author: Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Dumm, J., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Stevenson, B., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Baack, D., Babić, A., Banerjee, B., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Chai, Y., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Espiñera, E. Do Souto, Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Ramazani, V. Fallah, Fattorini, A., Fernández-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Godinović, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Fraga, B. Machado de Oliveira, Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Nöthe, M., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peñil, P., Peresano, M., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Sun, S., Surić, T., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Tsujimoto, S., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Will, M., Zarić, D., Aller, H. D., Aller, M. F., Carini, M. T., Horan, D., Jordan, B., Jorstad, Svetlana G., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Larionov, V. M., Larionova, E. G., Madejski, G., Marscher, Alan P., Max-Moerbeck, W., Moody, J. Ward, Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Readhead, A. C. S., Richards, J. L., Sadun, Alberto C., Sakamoto, T., Sigua, L. A., Smith, P. S., Talvikki, H., Tammi, J., Tornikoski, M., Troitsky, I. S., and Villata, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of February, 2010 when an extraordinary flare reaching a level of $\sim$27~Crab Units above 1~TeV was measured in very-high-energy (VHE) $\gamma$-rays with the VERITAS observatory. This is the highest flux state for Mrk 421 ever observed in VHE $\gamma$-rays. Data are analyzed from a coordinated campaign across multiple instruments including VHE $\gamma$-ray (VERITAS, MAGIC), high-energy (HE) $\gamma$-ray (Fermi-LAT), X-ray (Swift}, RXTE, MAXI), optical (including the GASP-WEBT collaboration and polarization data) and radio (Mets\"ahovi, OVRO, UMRAO). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare `decline' epochs. The main flare statistics allow 2-minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of $\sim$25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor ($\delta \gtrsim 33$) and the size of the emission region ($ \delta^{-1}R_B \lesssim 3.8\times 10^{13}\,\,\mbox{cm}$) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10-minute-binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship: from linear to quadratic to lack of correlation to anti-correlation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain by the classic single-zone synchrotron self-Compton model., Comment: 41 pages including 3 appendices, 13 figures; version accepted to Astrophysical Journal
Published: 2020
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9. Unravelling the complex behavior of Mrk 421 with simultaneous X-ray and VHE observations during an extreme flaring activity in April 2013

Author: MAGIC collaboration, Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Baack, D., Babic, A., Banerjee, B., de Almeida, U. Barres, Barrio, J. A., Gonzalez, J. Becerra, Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bosnjak, Z., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Del Puppo, F., Delfino, M., Delgado, J., Depaoli, D., Di Pierro, F., Di Venere, L., Espineira, E. Do Souto, Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Ramazani, V. Fallah, Fattorini, A., Ferrara, G., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Lopez, R. J. Garcia, Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinovic, N., Green, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Hutten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jouvin, L., Kajiwara, Y., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Loporchio, S., Fraga, B. Machado de Oliveira, Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Mazin, D., Mender, S., Micanovic, S., Miceli, D., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogues, L., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletic, L., Penil, P., Peresano, M., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Rhode, W., Ribo, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Snidaric, I., Sobczynska, D., Spolon, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Suric, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzic, T., Teshima, M., Torres-Alba, N., Tosti, L., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Zaric, D., groups, Other, Petropoulou, M., Finke, J., D'Ammando, F., Balokovic, M., Madejski, G., Mori, K., Puccetti, Simonetta, Leto, C., Perri, M., Verrecchia, F., Villata, M., Raiteri, C. M., Agudo, I., Bachev, R., Berdyugin, A., Blinov, D. A., Chanishvili, R., Chen, W. P., Chigladze, R., Damljanovic, G., Eswaraiah, C., Grishina, T. S., Ibryamov, S., Jordan, B., Jorstad, S. G., Joshi, M., Kopatskaya, E. N., Kurtanidze, O. M., Kurtanidze, S. O., Larionova, E. G., Larionova, L. V., Larionov, V. M., Latev, G., Lin, H. C., Marscher, A. P., Mokrushina, A. A., Morozova, D. A., Nikolashvili, M. G., Semkov, E., Smith, P. S., Strigachev, A., Troitskaya, Yu. V., Troitsky, I. S., Vince, O., Barnes, J., Guever, T., Moody, J. W., Sadun, A. C., Hovatta, T., Richards, J. L., Max-Moerbeck, W., Readhead, A. C. R., Lahteenmaki, A., Tornikoski, M., Tammi, J., Ramakrishnan, V., and Reinthal, R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on a multi-band variability and correlation study of the TeV blazar Mrk 421 during an exceptional flaring activity observed from 2013 April 11 to 2013 April 19. The study uses, among others, data from GASP-WEBT, Swift, NuSTAR, Fermi-LAT, VERITAS, and MAGIC. The large blazar activity, and the 43 hours of simultaneous NuSTAR and MAGIC/VERITAS observations, permitted variability studies on 15 minute time bins, and over three X-ray bands (3-7 keV, 7-30 keV and 30-80 keV) and three very-high-energy (>0.1 TeV, hereafter VHE) gamma-ray bands (0.2-0.4 TeV, 0.4-0.8 TeV and >0.8 TeV). We detected substantial flux variations on multi-hour and sub-hour timescales in all the X-ray and VHE gamma-ray bands. The characteristics of the sub-hour flux variations are essentially energy-independent, while the multi-hour flux variations can have a strong dependence on the energy of the X-ray and the VHE gamma rays. The three VHE bands and the three X-ray bands are positively correlated with no time-lag, but the strength and the characteristics of the correlation changes substantially over time and across energy bands. Our findings favour multi-zone scenarios for explaining the achromatic/chromatic variability of the fast/slow components of the light curves, as well as the changes in the flux-flux correlation on day-long timescales. We interpret these results within a magnetic reconnection scenario, where the multi-hour flux variations are dominated by the combined emission from various plasmoids of different sizes and velocities, while the sub-hour flux variations are dominated by the emission from a single small plasmoid moving across the magnetic reconnection layer., Comment: 46 pages, 17 figures, 9 tables, accepted for publication in ApJ Supplements
Published: 2020
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10. Multiwavelength behaviour of the blazar 3C279: decade-long study from $\gamma$-ray to radio

Author: Larionov, V. M., Jorstad, S. G., Marscher, A. P., Villata, M., Raiteri, C. M., Smith, P. S., Agudo, I., Savchenko, S. S., Morozova, D. A., Acosta-Pulido, J. A., Aller, M. F., Aller, H. D., Andreeva, T. S., Arkharov, A. A., Bachev, R., Bonnoli, G., Borman, G. A., Bozhilov, V., Calcidese, P., Carnerero, M. I., Carosati, D., Casadio, C., Chen, W. -P., Damljanovic, G., Dementyev, A. V., Di Paola, A., Frasca, A., Fuentes, A., Gómez, J. L., Gónzalez-Morales, P., Giunta, A., Grishina, T. S., Gurwell, M. A., Hagen-Thorn, V. A., Hovatta, T., Ibryamov, S., Joshi, M., Kiehlmann, S., Kim, J. -Y., Kimeridze, G. N., Kopatskaya, E. N., Kovalev, Yu. A., Kovalev, Y. Y., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Lázaro, C., Larionova, L. V., Larionova, E. G., Leto, G., Marchini, A., Matsumoto, K., Mihov, B., Minev, M., Mingaliev, M. G., Mirzaqulov, D., Dimitrova, R. V. Muñoz, Myserlis, I., Nikiforova, A. A., Nikolashvili, M. G., Nizhelsky, N. A., Ovcharov, E., Pressburger, L. D., Rakhimov, I. A., Righini, S., Rizzi, N., Sadakane, K., Sadun, A. C., Samal, M. R., Sanchez, R. Z., Semkov, E., Sergeev, S. G., Sigua, L. A., Slavcheva-Mihova, L., Sola, P., Sotnikova, Yu. V., Strigachev, A., Thum, C., Traianou, E., Troitskaya, Yu. V., Troitsky, I. S., Tsybulev, P. G., Vasilyev, A. A., Vince, O., Weaver, Z. R., Williamson, K. E., and Zhekanis, G. V.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We report the results of decade-long (2008-2018) $\gamma$-ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, $\it{Fermi}$ and $\it{Swift}$ data, as well as polarimetric and spectroscopic data. The X-ray and $\gamma$-ray light curves correlate well, with no delay > 3 hours, implying general co-spatiality of the emission regions. The $\gamma$-ray-optical flux-flux relation changes with activity state, ranging from a linear to a more complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz VLBA images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain $\gamma$-ray variability on very short time scales. The Mg II emission line flux in the `blue' and `red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands we find progressive delays of the most prominent light curve maxima with decreasing frequency, as expected from the frequency dependence of the $\tau=1$ surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at $\sim5$ GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet., Comment: 21 pages, 18 figures, accepted for publication in MNRAS
Published: 2020
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11. Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017

Author: D'Ammando, F., Raiteri, C. M., Villata, M., Acosta-Pulido, J. A., Agudo, I., Arkharov, A. A., Bachev, R., Baida, G. V., Benitez, E., Borman, G. A., Boschin, W., Bozhilov, V., Butuzova, M. S., Calcidese, P., Carnerero, M. I., Carosati, D., Casadio, C., Castro-Segura, N., Chen, W. -P., Damljanovic, G., Di Paola, A., Echevarria, J., Efimova, N. V., Ehgamberdiev, Sh. A., Espinosa, C., Fuentes, A., Giunta, A., Gomez, J. L., Grishina, T. S., Gurwell, M. A., Hiriart, D., Jermak, H., Jordan, B., Jorstad, S. G., Joshi, M., Kimeridze, G. N., Kopatskaya, E. N., Kuratov, K., Kurtanidze, O. M., Kurtanidze, S. O., Lahteenmaki, A., Larionov, V. M., Larionova, E. G., Larionova, L. V., Lazaro, C., Lin, C. S., Malmrose, M. P., Marscher, A. P., Matsumoto, K., McBreen, B., Michel, R., Mihov, B., Minev, M., Mirzaqulov, D. O., Molina, S. N., Moody, J. W., Morozova, D. A., Nazarov, S. V., Nikiforova, A. A., Nikolashvili, M. G., Ohlert, J. M., Okhmat, N., Ovcharov, E., Pinna, F., Polakis, T. A., Protasio, C., Pursimo, T., Redondo-Lorenzo, F. J., Rizzi, N., Rodriguez-Coira, G., Sadakane, K., Sadun, A. C., Samal, M. R., Savchenko, S. S., Semkov, E., Sigua, L., Skiff, B. A., Slavcheva-Mihova, L., Smith, P. S., Steele, I. A., Strigachev, A., Tammi, J., Thum, C., Tornikoski, M., Troitskaya, Yu. V., Troitsky, I. S., Vasilyev, A. A., Vince, O., Hovatta, T., Kiehlmann, S., Max-Moerbeck, W., Readhead, A. C. S., Reeves, R., Pearson, T. J., Mufakharov, T., Sotnikova, Yu. V., and Mingaliev, M. G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi ($\gamma$ rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented $\gamma$-ray flaring activity was observed during 2016 November-2017 February, with four major outbursts. A peak flux of (2158 $\pm$ 63)$\times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$, corresponding to a luminosity of (2.2 $\pm$ 0.1)$\times$10$^{50}$ erg s$^{-1}$, was reached on 2016 December 28. These four $\gamma$-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and $\gamma$-ray activity is found. The $\gamma$-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This $\gamma$-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission., Comment: 24 pages, 18 figures, and 4 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society
Published: 2019
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12. The extreme HBL behaviour of Markarian 501 during 2012

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Babić, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., Berti, A., Bhattacharyya, W., Blanch, O., Bonnoli, G., Carosi, R., Carosi, A., Chatterjee, A., Colak, S. M., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Cumani, P., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Doert, M., Domínguez, A., Prester, D. Dominis, Doro, M., Glawion, D. Eisenacher, Engelkemeier, M., Ramazani, V. Fallah, Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Gaug, M., Giammaria, P., Godinović, N., Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hassan, T., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Ishio, K., Konno, Y., Kubo, H., Kushida, J., Kuveždić, D., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., Maggio, C., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Minev, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moreno, V., Moretti, E., Nagayoshi, T., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Paiano, S., Palacio, J., Paneque, D., Paoletti, R., Paredes, J. M., Pedaletti, G., Peresano, M., Perri, L., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saito, T., Satalecka, K., Schroeder, S., Schweizer, T., Shore, S. N., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Treves, A., Tsujimoto, S., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Ward, J. E., Will, M., Zarić, D., Arbet-Engels, A., Baack, D., Balbo, M., Biland, A., Blank, M., Bretz, T., Bruegge, K., Bulinski, M., Buss, J., Dmytriiev, A., Dorner, D., Einecke, S., Elsaesser, D., Herbst, T., Hildebrand, D., Kortmann, L., Linhoff, L., Mahlke, M., Mannheim, K., Mueller, S. A., Neise, D., Neronov, A., Noethe, M., Oberkirch, J., Paravac, A., Rhode, W., Schleicher, B., Schulz, F., Sedlaczek, K., Shukla, A., Sliusar, V., Walter, R., Archer, A., Benbow, W., Bird, R., Brose, R., Buckley, J. H., Bugaev, V., Christiansen, J. L., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Finley, J. P., Gillanders, G. H., Gueta, O., Hanna, D., Hervet, O., Holder, J., Hughes, G., Hütten, M., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Lin, T. T. Y., Maier, G., McArthur, S., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Sushch, I., Tyler, J., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhel, A., Williams, D. A., Williamson, T. J, Zitzer, B., Perri, M., Verrecchia, F., Leto, C., Villata, M., Raiteri, C. M., Jorstad, S. G., Larionov, V. M., Blinov, D. A., Grishina, T. S., Kopatskaya, E. N., Larionova, E. G., Nikiforova, A. A., Morozova, D. A., Troitskaya, Yu. V., Troitsky, I. S., Kurtanidze, O. M., Nikolashvili, M. G., Kurtanidze, S. O., Kimeridze, G. N., Chigladze, R. A., Strigachev, A., Sadun, A. C., Moody, J. W., Chen, W. P., Lin, H. C., Acosta-Pulido, J. A., Arévalo, M. J., Carnerero, M. I., González-Morales, P. A., Manilla-Robles, A., Jermak, H., Steele, I., Mundel, C., Benítez, E., Hiriart, D., Smith, P. S., Max-Moerbeck, W., Readhead, A. C. S., Richards, J. L., Hovatta, T., Lähteenmäki, A., Tornikoski, M., Tammi, J., Georganopoulos, M., and Baring, M. G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: A multiwavelength campaign was organized to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of $\sim$0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was $\sim$3 CU, and the peak of the high-energy spectral component was found to be at $\sim$2 TeV. This study reports very hard X-ray spectra, and the hardest VHE spectra measured to date for Mrk 501. The fractional variability was found to increase with energy, with the highest variability occurring at VHE, and a significant correlation between the X-ray and VHE bands. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency- peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The one-zone synchrotron self-Compton (SSC) scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behaviour seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays., Comment: 25 pages, 9 figures, accepted for publication in A&A. Corresponding authors: Gareth Hughes (gareth.hughes@cfa.harvard.edu), David Paneque (dpaneque@mppmu.mpg.de), Amit Shukla (amit.shukla@astro.uni-wuerzburg.de)
Published: 2018
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13. Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., Berti, A., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Buson, S., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Wilhelmi, E. de Ona, Di Pierro, F., Doert, M., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Engelkemeier, M., Ramazani, V. Fallah, Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Godinović, N., Munoz, A. González, Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Noda, K., Nogués, L., Overkemping, A., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Pedaletti, G., Peresano, M., Perri, L., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Satalecka, K., Schröder, S., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Vanzo, G., Verguilov, V., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zanin, R., Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Connolly, M. P., Cui, W., Dickinson, H. J., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Flinders, A., Fortson, L., Gillanders, G. H., Griffin, S., Grube, J., Hütten, M., Hanna, D., Holder, J., Humensky, T. B., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Maier, G., McCann, A., Moriarty, P., Mukherjee, R., Nieto, D., O'Brien, S., Ong, R. A., Otte, N., Park, N., Perkins, J., Pichel, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Telezhinsky, I., Tucci, J. V., Tyler, J., Wakely, S. P., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Razzaque, S., Villata, M., Raiteri, C. M., Aller, H. D., Aller, M. F., Larionov, V. M., Arkharov, A. A., Blinov, D. A., Efimova, N. V., Grishina, T. S., Hagen-Thorn, V. A., Kopatskaya, E. N., Larionova, L. V., Larionova, E. G., Morozova, D. A., Troitsky, I. S., Ligustri, R., Calcidese, P., Berdyugin, A., Kurtanidze, O. M., Nikolashvili, M. G., Kimeridze, G. N., Sigua, L. A., Kurtanidze, S. O., Chigladze, R. A., Chen, W. P., Koptelova, E., Sakamoto, T., Sadun, A. C., Moody, J. W., Pace, C., Pearson III, R., Yatsu, Y., Mori, Y., Carraminyana, A., Carrasco, L., de la Fuente, E., Norris, J. P., Smith, P. S., Wehrle, A., Gurwell, M. A., Zook, Alma, Pagani, C., Perri, M., Capalbi, M., Cesarini, A., Krimm, H. A., Kovalev, Y. Y., Kovalev, Yu. A., Ros, E., Pushkarev, A. B., Lister, M. L., Sokolovsky, K. V., Kadler, M., Piner, G., Lähteenmäki, A., Tornikoski, M., Angelakis, E., Krichbaum, T. P., Nestoras, I., Fuhrmann, L, Zensus, J. A., Cassaro, P., Orlati, A., Maccaferri, G., Leto, P., Giroletti, M., Richards, J. L., Max-Moerbeck, W., and Readhead, A. C. S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1 which includes, among other instruments, MAGIC, VERITAS, Whipple 10-m, Fermi-LAT, RXTE, Swift, GASP-WEBT and VLBA. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found in the acquired data set. The higher variability in the very high energy (>100 GeV, VHE) gamma-ray emission and the lack of correlation with the X-ray emission indicate that the highest-energy electrons that are responsible for the VHE gamma-rays do not make a dominant contribution to the ~1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the synchrotron self-Compton (SSC) scenarios. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters. We find that there is some degeneracy in both the one-zone and the two-zone SSC scenarios that were probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The SSC model grid-scan shows that the flaring activity around 2009 May 22 cannot be modeled adequately with a one-zone SSC scenario, while it can be suitably described within a two-independent-zone SSC scenario. The observation of an electric vector polarization angle rotation coincident with the gamma-ray flare from 2009 May 1 resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties., Comment: 33 pages, 15 figures, accepted for publication in A&A. Corresponding authors: Marlene Doert (marlene.doert@tu-dortmund.de) and David Paneque (dpaneque@mppmu.mpg.de)
Published: 2016
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14. Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales

Author: Bhatta, G., Stawarz, Ł., Ostrowski, M., Markowitz, A., Akitaya, H., Arkharov, A. A., Bachev, R., Benítez, E., Borman, G. A., Carosati, D., Cason, A. D., Chanishvili, R., Damljanovic, G., Dhalla, S., Frasca, A., Hiriart, D., Hu, S-M., Itoh, R., Jableka, D., Jorstad, S., Jovanovic, M. D., Kawabata, K. S., Klimanov, S. A., Kurtanidze, O., Larionov, V. M., Laurence, D., Leto, G., Marscher, A. P., Moody, J. W., Moritani, Y., Ohlert, J. M., Di Paola, A., Raiteri, C. M., Rizzi, N., Sadun, A. C., Sasada, M., Sergeev, S., Strigachev, A., Takaki, K., Troitsky, I. S., Ui, T., Villata, M., Vince, O., Webb, J. R., Yoshida, M., and Zola, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Here we report on the results of the WEBT photo-polarimetric campaign targeting the blazar S5~0716+71, organized in March 2014 to monitor the source simultaneously in BVRI and near IR filters. The campaign resulted in an unprecedented dataset spanning $\sim 110$\,h of nearly continuous, multi-band observations, including two sets of densely sampled polarimetric data mainly in R filter. During the campaign, the source displayed pronounced variability with peak-to-peak variations of about $30\%$ and "bluer-when-brighter" spectral evolution, consisting of a day-timescale modulation with superimposed hourlong microflares characterized by $\sim 0.1$\,mag flux changes. We performed an in-depth search for quasi-periodicities in the source light curve; hints for the presence of oscillations on timescales of $\sim 3$\,h and $\sim 5$\,h do not represent highly significant departures from a pure red-noise power spectrum. We observed that, at a certain configuration of the optical polarization angle relative to the positional angle of the innermost radio jet in the source, changes in the polarization degree led the total flux variability by about 2\,h; meanwhile, when the relative configuration of the polarization and jet angles altered, no such lag could be noted. The microflaring events, when analyzed as separate pulse emission components, were found to be characterized by a very high polarization degree ($> 30\%$) and polarization angles which differed substantially from the polarization angle of the underlying background component, or from the radio jet positional angle. We discuss the results in the general context of blazar emission and energy dissipation models., Comment: 16 pages, 17 Figures; ApJ accepted
Published: 2016
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15. Exceptional outburst of the blazar CTA 102 in 2012: The GASP-WEBT campaign and its extension

Author: Larionov, V. M., Villata, M., Raiteri, C. M., Jorstad, S. G., Marscher, A. P., Agudo, I., Smith, P. S., Acosta-Pulido, J. A., Arévalo, M. J., Arkharov, A. A., Bachev, R., Blinov, D. A., Borisov, G., Borman, G. A., Bozhilov, V., Bueno, A., Carnerero, M. I., Carosati, D., Casadio, C., Chen, W. P., Clemens, D. P., Di Paola, A., Ehgamberdiev, Sh. A., Gómez, J. L., González-Morales, P. A, Griñón-Marín, A., Grishina, T. S., Hagen-Thorn, V. A., Ibryamov, S., Itoh, R., Kopatskaya, E. N., Koptelova, E., Lázaro, C., Larionova, E. G., Larionova, L. V., Manilla-Robles, A., Metodieva, Y., Milanova, Yu. V., Mirzaqulov, D. O., Molina, S. N., Morozova, D. A., Nazarov, S. V., Ovcharov, E., Peneva, S., Ros, J. A., Sadun, A. C., Savchenko, S. S., Semkov, E., Sergeev, S. G., Strigachev, A., Troitskaya, Yu. V., and Troitsky, I. S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September-October. The flare was tracked from gamma-ray to near-infrared frequencies, including Fermi and Swift data as well as photometric and polarimetric data from several observatories. An intensive GASP-WEBT collaboration campaign in optical and NIR bands, with an addition of previously unpublished archival data and extension through fall 2015, allows comparison of this outburst with the previous activity period of this blazar in 2004-2005. We find remarkable similarity between the optical and gamma-ray behaviour of CTA 102 during the outburst, with a time lag between the two light curves of ~1 hour, indicative of co-spatiality of the optical and gamma-ray emission regions. The relation between the gamma-ray and optical fluxes is consistent with the SSC mechanism, with a quadratic dependence of the SSC gamma-ray flux on the synchrotron optical flux evident in the post-outburst stage. However, the gamma-ray/optical relationship is linear during the outburst; we attribute this to changes in the Doppler factor. A strong harder-when-brighter spectral dependence is seen both the in gamma-ray and optical non-thermal emission. This hardening can be explained by convexity of the UV-NIR spectrum that moves to higher frequencies owing to an increased Doppler shift as the viewing angle decreases during the outburst stage. The overall pattern of Stokes parameter variations agrees with a model of a radiating blob or shock wave that moves along a helical path down the jet., Comment: 11 pages, 14 figures, accepted in MNRAS
Published: 2016
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16. Long-term multi-wavelength variability and correlation study of Markarian 421 from 2007 to 2009

Author: MAGIC Collaboration, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Buson, S., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Wilhelmi, E. de Oña, Di Pierro, F., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Godinović, N., Muñoz, A. González, Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Noda, K., Nogués, L., Orito, R., Overkemping, A., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Pedaletti, G., Perri, L., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Satalecka, K., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Takalo, L., Takami, H., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Verguilov, V., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zanin, R., Blinov, D. A., Chen, W. P., Efimova, N. V., Forné, E., Grishina, T. S., Hovatta, T., Jordan, B., Kimeridze, G. N., Kopatskaya, E. N., Koptelova, E., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmaäki, A., Larionov, V. M., Larionova, E. G., Larionova, L. V., Ligustri, R., Lin, H. C., McBreen, B., Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Ros, J. A., Sadun, A. C., Sigua, L. A., Tornikoski, M., Troitsky, I. S., and Villata, M.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We study the multi-band variability and correlations of the TeV blazar Mrk 421 on year time scales, which can bring additional insight on the processes responsible for its broadband emission. We observed Mrk 421 in the very high energy (VHE) gamma-ray range with the Cherenkov telescope MAGIC-I from March 2007 to June 2009 for a total of 96 hours of effective time after quality cuts. The VHE flux variability is quantified with several methods, including the Bayesian Block algorithm, which is applied to data from Cherenkov telescopes for the first time. The 2.3 year long MAGIC light curve is complemented with data from the Swift/BAT and RXTE/ASM satellites and the KVA, GASP-WEBT, OVRO, and Mets\"ahovi telescopes from February 2007 to July 2009, allowing for an excellent characterisation of the multi-band variability and correlations over year time scales. Mrk 421 was found in different gamma-ray emission states during the 2.3 year long observation period. Flares and different levels of variability in the gamma-ray light curve could be identified with the Bayesian Block algorithm. The same behaviour of a quiet and active emission was found in the X-ray light curves measured by Swift/BAT and the RXTE/ASM, with a direct correlation in time. The behaviour of the optical light curve of GASP-WEBT and the radio light curves by OVRO and Mets\"ahovi are different as they show no coincident features with the higher energetic light curves and a less variable emission. The fractional variability is overall increasing with energy. The comparable variability in the X-ray and VHE bands and their direct correlation during both high- and low-activity periods spanning many months show that the electron populations radiating the X-ray and gamma-ray photons are either the same, as expected in the Synchrotron-Self-Compton mechanism, or at least strongly correlated, as expected in electromagnetic cascades., Comment: Corresponding authors: Ann-Kristin Overkemping (ann-kristin.overkemping@tu-dortmund.de), Marina Manganaro (manganaro@iac.es), Diego Tescaro (diego.tescaro@gmail.com), To be published in Astronomy&Astrophysics (A&A), 12 pages, 9 figures
Published: 2016
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17. Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013

Author: Baloković, M., Paneque, D., Madejski, G., Furniss, A., Chiang, J., team, the NuSTAR, Ajello, M., Alexander, D. M., Barret, D., Blandford, R., Boggs, S. E., Christensen, F. E., Craig, W. W., Forster, K., Giommi, P., Grefenstette, B. W., Hailey, C. J., Harrison, F. A., Hornstrup, A., Kitaguchi, T., Koglin, J. E., Madsen, K. K., Mao, P. H., Miyasaka, H., Mori, K., Perri, M., Pivovaroff, M. J., Puccetti, S., Rana, V., Stern, D., Tagliaferri, G., Urry, C. M., Westergaard, N. J., Zhang, W. W., Zoglauer, A., collaboration, the VERITAS, Archambault, S., Archer, A. A., Barnacka, A., Benbow, W., Bird, R., Buckley, J., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Huetten, M., Haakansson, N., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Maier, G., McArthur, S., Meagher, K., Moriarty, P., Nelson, T., Nieto, D., Ong, R. A., Park, N., Pohl, M., Popkow, A., Pueschel, E., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Todd, N. W., Tucci, J. V., Tyler, J., Vincent, S., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., collaboration, the MAGIC, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J., González, J. Becerra, Bednarek, W., Bernardini, E., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., de Angelis, A., De Lotto, B., Wilhelmi, E. D. de Oña, Mendez, C. Delgado, Di Pierro, F., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Eisenacher, D., Godinović, N., Muñoz, A. González, Guberman, D., Hahn, A., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Lorenz, E., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Nievas-Rosillo, M., Nilsson, K., Nishijima, K., Noda, K., Orito, R., Overkemping, A., Paiano, S., Palacio, S., Palatiello, M., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Satalecka, K., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Takalo, L. O., Takami, H., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Verguilov, V., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zanin, R., collaborators, external, Perkins, J., Verrecchia, F., Leto, C., Böttcher, M., Villata, M., Raiteri, C. M., Acosta-Pulido, J. A., Bachev, R., Berdyugin, A., Blinov, D. A., Carnerero, M. I., Chen, W. P., Chinchilla, P., Damljanovic, G., Eswaraiah, C., Grishina, T. S., Ibryamov, S., Jordan, B., Jorstad, S. G., Joshi, M., Kopatskaya, E. N., Kurtanidze, O. M., Kurtanidze, S. O., Larionova, E. G., Larionova, L. V., Larionov, V. M., Latev, G., Lin, H. C., Marscher, A. P., Mokrushina, A. A., Morozova, D. A., Nikolashvili, M. G., Semkov, E., Strigachev, A., Troitskaya, Yu. V., Troitsky, I. S., Vince, O., Barnes, J., Güver, T., Moody, J. W., Sadun, A. C., Sun, S., Hovatta, T., Richards, J. L., Max-Moerbeck, W., Readhead, A. C., Lähteenmäki, A., Tornikoski, M., Tammi, J., Ramakrishnan, V., Reinthal, R., Angelakis, E., Fuhrmann, L., Myserlis, I., Karamanavis, V., Sievers, A., Ungerechts, H., and Zensus, J. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79 keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep power law with a photon index of approximately 3, with no evidence for an exponential cutoff or additional hard components up to about 80 keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure which relates to the two bumps of the broadband SED. In each bump, the variability increases with energy which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi-band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in-situ electron acceleration, and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states., Comment: 32 pages, 14 figures; accepted for publication in ApJ
Published: 2015
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18. First NuSTAR Observations of Mrk 501 within a Radio to TeV Multi-Instrument Campaign

Author: Furniss, A., Noda, K., Boggs, S., Chiang, J., Christensen, F., Craig, W., Giommi, P ., Hailey, C., Harisson, F., Madejski, G., Nalewajko, K., Perri, M., Stern, D., Urry, M., Verrecchia, F., Zhang, W., Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., Gonzalez, J. Becerra, Bednarek, W., Bernardini, E., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Wilhelmi, E. de Ona, Mendez, C. Delgado, Di Pierro, F., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Fernandez-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., Lopez, R. J. Garcia, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Godinovic, N., Munoz, A. Gonzalez, Guberman, D., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kellermann, H., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Lorenz, E., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martinez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Orito, R., Overkemping, A., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reinthal, R., Rhode, W., Ribo, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Saito, K., Satalecka, K., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpaa, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Takalo, L., Takami, H., Tavecchio, F., Temnikov, P., Terzic, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Verguilov, V., Vovk, I., Will, M., Zanin, R., Archer, A., Benbow, W., Bird, R., Biteau, J., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Gerard, L., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Haakansson, N., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Lin, T. T. Y., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Park, N., Petry, D., Pohl, M., Popkow, A., Ragan, K., Ratliff, G., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., Fuhrmann, O. Vince L., Angelakis, E., Karamanavis, V., Myserlis, I., Krichbaum, T. P., Zensus, J. A., Ungerechts, H., Sievers, A., Bachev, R., Bottcher, M., Chen, W. P., Damljanovic, G., Eswaraiah, C., Guver, T., Hovatta, T., Hughes, Z., Ibryamov, S. . I., Joner, M. D., Jordan, B., Jorstad, S. G., Joshi, M., Kataoka, J., Kurtanidze, O. M., Kurtanidze, S. O., Lahteenmaki, A., Latev, G., Lin, H. C., Larionov, V. M., Mokrushina, A. A., Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Ramakrishnan, V., Readhead, A. C. R., Sadun, A. C., Sigua, L. A., Semkov, E. H., Strigachev, A., Tammi, J., Tornikoski, M., Troitsky, Y. V. Troitskaya I. S., and Villata, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 1 April and 10 August 2013, including the first detailed characterization of the synchrotron peak with Swift and NuSTAR. During the campaign, the nearby BL Lac object was observed in both a quiescent and an elevated state. The broadband campaign includes observations with NuSTAR, MAGIC, VERITAS, the Fermi Large Area Telescope (LAT), Swift X-ray Telescope and UV Optical Telescope, various ground-based optical instruments, including the GASP-WEBT program, as well as radio observations by OVRO, Mets\"ahovi and the F-Gamma consortium. Some of the MAGIC observations were affected by a sand layer from the Saharan desert, and had to be corrected using event-by-event corrections derived with a LIDAR (LIght Detection And Ranging) facility. This is the first time that LIDAR information is used to produce a physics result with Cherenkov Telescope data taken during adverse atmospheric conditions, and hence sets a precedent for the current and future ground-based gamma-ray instruments. The NuSTAR instrument provides unprecedented sensitivity in hard X-rays, showing the source to display a spectral energy distribution between 3 and 79 keV consistent with a log-parabolic spectrum and hard X-ray variability on hour timescales. None (of the four extended NuSTAR observations) shows evidence of the onset of inverse-Compton emission at hard X-ray energies. We apply a single-zone equilibrium synchrotron self-Compton model to five simultaneous broadband spectral energy distributions. We find that the synchrotron self-Compton model can reproduce the observed broadband states through a decrease in the magnetic field strength coinciding with an increase in the luminosity and hardness of the relativistic leptons responsible for the high-energy emission., Comment: Accepted for publication in ApJ
Published: 2015
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19. The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies

Author: MAGIC Collaboration, Aleksić, J., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Fidalgo, D. Carreto, Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Mendez, C. Delgado, Doert, M., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Eisenacher, D., Elsaesser, D., Farina, E., Ferenc, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giavitto, G., Godinović, N., noz, A. González Mu\, Gozzini, S. R., Hadamek, A., Hadasch, D., Herrero, A., Hildebrand, D., Hose, J., Hrupec, D., Idec, W., Kadenius, V., Kellermann, H., Knoetig, M. L., Krause, J., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Longo, F., Lombardi, S., López, M., López-Coto, R., López-Oramas, A., Lorenz, E., Lozano, I., Makariev, M., Mallot, K., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Meucci, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Munar-Adrover, P., Nakajima, D., Niedzwiecki, A., Nilsson, K., Nowak, N., Orito, R., Overkemping, A., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Partini, S., Persic, M., Prada, F., Moroni, P. G. Prada, Prandini, E., Preziuso, S., Puljak, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Rügamer, S., Saggion, A., Saito, K., Salvati, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Spanier, F., Stamatescu, V., Stamerra, A., Steinbring, T., Storz, J., Sun, S., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Tibolla, O., Torres, D. F., Toyama, T., Treves, A., Uellenbeck, M., Vogler, P., Wagner, R. M., Zandanel, F., Zanin, R., collaboration, VERITAS, Archambault, S., Behera, B., Beilicke, M., Benbow, W., Bird, R., Buckley, J. H., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Collins-Hughes, E., Cui, W., Dumm, J., Eisch, J. D., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., McArthur, S., Meagher, K., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Park, N., Pichel, A., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Theiling, M., Tucci, J. V., Tyler, J., Varlotta, A., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., collaborators, External, Villata, M., Raiteri, C., Aller, H. D., Aller, M. F., Chen, W. P., Jordan, B., Koptelova, E., Kurtanidze, O. M., Lähteenmäki, A., McBreen, B., Larionov, V. M., Lin, C. S., Nikolashvili, M. G., Angelakis, E., Capalbi, M., nana, A. Carrami\, Carrasco, L., Cassaro, P., Cesarini, A., Fuhrmann, L., Giroletti, M., Hovatta, T., Krichbaum, T. P., Krimm, H. A., Max-Moerbeck, W., Moody, J. W., Maccaferri, G., Mori, Y., Nestoras, I., Orlati, A., Pace, C., Pearson, R., Perri, M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Tammi, J., Tornikoski, M., Yatsu, Y., and Zook, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical/UV and X-rays extending over the duration of the campaign. The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk421 during non-flaring activity. Such a temporally extended X-ray/VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies., Comment: Accepted for publication in A&A, 18 pages, 14 figures (v2 has a small modification in the acknowledgments, and also corrects a typo in the field "author" in the metadata)
Published: 2015
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20. Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010

Author: The MAGIC Collaboration, Aleksić, J., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., Biasuzzi, B., Biland, A., Blanch, O., Boller, A., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Wilhelmi, E. de Oña, Mendez, C. Delgado, Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Eisenacher, D., Elsaesser, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Godinović, N., Muñoz, A. González, Gozzini, S. R., Hadasch, D., Hanabata, Y., Hayashida, M., Herrera, J., Hildebrand, D., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kadenius, V., Kellermann, H., Knoetig, M. L., Kodani, K., Konno, Y., Krause, J., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Lombardi, S., López, M., López-Coto, R., López-Oramas, A., Lorenz, E., Lozano, I., Makariev, M., Mallot, K., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Munar-Adrover, P., Nakajima, D., Niedzwiecki, A., Nilsson, K., Nishijima, K., Noda, K., Orito, R., Overkemping, A., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Rügamer, S., Saito, T., Saito, K., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Sun, S., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Spanier, F., Stamatescu, V., Stamerra, A., Steinbring, T., Steinke, B., Storz, J., Strzys, M., Takalo, L., Takami, H., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Tibolla, O., Torres, D. F., Toyama, T., Treves, A., Uellenbeck, M., Vogler, P., Zanin, R., Collaboration, The VERITAS, Archambault, S., Archer, A., Beilicke, M., Benbow, W., Berger, K., Bird, R., Biteau, J., Buckley, J. H., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Collins-Hughes, E., Cui, W., Eisch, J. D., Falcone, A., Feng, Q., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Gyuk, G., Håkansson, N., Holder, J., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Kieda, D., Lang, M. J., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Ong, R. A., Otte, A. N., Perkins, J. S., Pichel, A., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Ragan, K., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Wakely, S. P., Welsing, R., Wilhelm, A., Williams, D. A., Collaborators, External, Buson, S., Finke, J., Villata, M., Raiteri, C., Aller, H. D., Aller, M. F., Cesarini, A., Chen, W. P., Gurwell, M. A., Jorstad, S. G., Kimeridze, G. N., Koptelova, E., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Larionov, V. M., Larionova, E. G., Lin, H. C., McBreen, B., Moody, J. W., Morozova, D. A., Marscher, A. P., Max-Moerbeck, W., Nikolashvili, M. G., Perri, M., Readhead, A. C. S., Richards, J. L., Ros, J. A., Sadun, A. C., Sakamoto, T., Sigua, L. A., Smith, P. S., Tornikoski, M., Troitsky, I. S., Wehrle, A. E., and Jordan, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE, E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ($\delta$, $B$ and $R$), in addition to the parameters related to the particle population., Comment: Published in A&A, 30 pages, 15 figures, 6 tables. Online-data: multi-wavelength light curves (data in Fig. 1) and broadband spectral energy distributions (the data in Figs. 6, and B1-B4) are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A22. Corresponding authors: David Paneque (dpaneque@mpp.mpg.de), Shangyu Sun (sysun@mpp.mpg.de), Hajime Takami (takami@post.kek.jp)
Published: 2014
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21. VERITAS Collaboration Contributions to the 32nd International Cosmic Ray Conference

Author: The VERITAS Collaboration, Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Böttcher, M., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Christiansen, J. L., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickherber, R., Duke, C., Dwarkadas, V. V., Errando, M., Falcone, A., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Griffin, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Huan, H., Hughes, G., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Lyutikov, M., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., McCutcheon, M., Moriarty, P., Mukherjee, R., Nunez, P. D, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pizlo, F., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rovero, A. C., Ruppel, J., Sadun, A. C., Saxon, D. B., Schroedter, M., Sembroski, G. H., Şentürk, G. D., Smith, A. W., Staszak, D., Tešić, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Tyler, J., Varlotta, A., Vassiliev, V. V., Vincent, S., Vivier, M., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Compilation of papers contributed by the VERITAS Collaboration to the 32nd International Cosmic Ray Conference, held 11-18 August 2011 in Beijing, China., Comment: 1 html page. ICRC 2011, Beijing, China. A full list of authors and collaborating institutions can be found at http://veritas.sao.arizona.edu/conferences/authors?icrc2011
Published: 2011

22. VERITAS: Status and Highlights

Author: Holder, J., Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Böttcher, M., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Christiansen, J. L., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickherber, R., Duke, C., Dwarkadas, V. V., Errando, M., Falcone, A., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Griffin, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Huan, H., Hughes, G., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Lyutikov, M., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., McCutcheon, M., Moriarty, P., Mukherjee, R., Nunez, P. D, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pizlo, F., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rovero, A. C., Ruppel, J., Sadun, A. C., Saxon, D. B., Schroedter, M., Sembroski, G. H., Şentürk, G. D., Smith, A. W., Staszak, D., Tešić, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Tyler, J., Varlotta, A., Vassiliev, V. V., Vincent, S., Vivier, M., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The VERITAS telescope array has been operating smoothly since 2007, and has detected gamma-ray emission above 100 GeV from 40 astrophysical sources. These include blazars, pulsar wind nebulae, supernova remnants, gamma-ray binary systems, a starburst galaxy, a radio galaxy, the Crab pulsar, and gamma-ray sources whose origin remains unidentified. In 2009, the array was reconfigured, greatly improving the sensitivity. We summarize the current status of the observatory, describe some of the scientific highlights since 2009, and outline plans for the future., Comment: Presented at the 32nd ICRC, Beijing, 2011
Published: 2011
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23. The brightest gamma-ray flaring blazar in the sky: AGILE and multi-wavelength observations of 3C 454.3 during November 2010

Author: Vercellone, S., Striani, E., Vittorini, V., Donnarumma, I., Pacciani, L., Pucella, G., Tavani, M., Raiteri, C. M., Villata, M., Romano, P., Fiocchi, M., Bazzano, A., Bianchin, V., Ferrigno, C., Maraschi, L., Pian, E., Türler, M., Ubertini, P., Bulgarelli, A., Chen, A. W., Giuliani, A., Longo, F., Barbiellini, G., Cardillo, M., Cattaneo, P. W., Del Monte, E., Evangelista, Y., Feroci, M., Ferrari, A., Fuschino, F., Gianotti, F., Giusti, M., Lazzarotto, F., Pellizzoni, A., Piano, G., Pilia, M., Rapisarda, M., Rappoldi, A., Sabatini, S., Soffitta, P., Trifoglio, M., Trois, A., Giommi, P., Lucarelli, F., Pittori, C., Santolamazza, P., Verrecchia, F., Agudo, I., Aller, H. D., Aller, M. F., Arkharov, A. A., Bach, U., Berdyugin, A., Borman, G. A., Chigladze, R., Efimov, Yu. S., Efimova, N. V., Gómez, J. L., Gurwell, M. A., McHardy, I. M., Joshi, M., Kimeridze, G. N., Krajci, T., Kurtanidze, O. M., Kurtanidze, S. O., Larionov, V. M., Lindfors, E., Molina, S. N., Morozova, D. A., Nazarov, S. V., Nikolashvili, M. G., Nilsson, K., Pasanen, M., Reinthal, R., Ros, J. A., Sadun, A. C., Sakamoto, T., Sallum, S., Sergeev, S. G., Schwartz, R. D., Sigua, L. A., Sillanpää, A., Sokolovsky, K. V., Strelnitski, V., Takalo, L., Taylor, B., and Walker, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one gamma-ray flare per year, becoming the most active gamma-ray blazar in the sky. We present for the first time the multi-wavelength AGILE, SWIFT, INTEGRAL, and GASP-WEBT data collected in order to explain the extraordinary gamma-ray flare of 3C 454.3 which occurred in November 2010. On 2010 November 20 (MJD 55520), 3C 454.3 reached a peak flux (E>100 MeV) of F_gamma(p) = (6.8+-1.0)E-5 ph/cm2/s on a time scale of about 12 hours, more than a factor of 6 higher than the flux of the brightest steady gamma-ray source, the Vela pulsar, and more than a factor of 3 brighter than its previous super-flare on 2009 December 2-3. The multi-wavelength data make a thorough study of the present event possible: the comparison with the previous outbursts indicates a close similarity to the one that occurred in 2009. By comparing the broadband emission before, during, and after the gamma-ray flare, we find that the radio, optical and X-ray emission varies within a factor 2-3, whereas the gamma-ray flux by a factor of 10. This remarkable behavior is modeled by an external Compton component driven by a substantial local enhancement of soft seed photons., Comment: Accepted for publication in ApJ Letters. 18 Pages, 4 Figures, 1 Table
Published: 2011
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24. TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008

Author: Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Cui, W., Dickherber, R., Duke, C., Falcone, A., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., Maier, G., McArthur, S., McCutcheon, M., Moriarty, P., Ong, R. A., Otte, A. N., Ouellette, M., Pandel, D., Perkins, J. S., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Rovero, A. C., Schroedter, M., Sembroski, G. H., Senturk, G. Demet, Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., Zitzer, B., Garson, A., Lee, K., Sadun, A. C., Carini, M., Barnaby, D., Cook, K., Maune, J., Pease, A., Smith, S., Walters, R., Berdyugin, A., Lindfors, E., Nilsson, K., Pasanen, M., Sainio, J., Sillanpaa, A., Takalo, L. O., Villforth, C., Montaruli, T., Baker, M., Lahteenmaki, A., Tornikoski, M., Hovatta, T., Nieppola, E., Aller, H. D., and Aller, M. F.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on TeV gamma-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10m Cherenkov telescope. The excellent sensitivity of VERITAS allowed us to sample the TeV gamma-ray fluxes and energy spectra with unprecedented accuracy where Mrk 421 was detected in each of the pointings. A total of 47.3 hrs of VERITAS and 96 hrs of Whipple 10m data were acquired between January 2006 and June 2008. We present the results of a study of the TeV gamma-ray energy spectra as a function of time, and for different flux levels. On May 2nd and 3rd, 2008, bright TeV gamma-ray flares were detected with fluxes reaching the level of 10 Crab. The TeV gamma-ray data were complemented with radio, optical, and X-ray observations, with flux variability found in all bands except for the radio waveband. The combination of the RXTE and Swift X-ray data reveal spectral hardening with increasing flux levels, often correlated with an increase of the source activity in TeV gamma-rays. Contemporaneous spectral energy distributions were generated for 18 nights, each of which are reasonably described by a one-zone SSC model., Comment: 30 pages, 12 figures, accepted by ApJ
Published: 2011
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25. Another look at the BL Lacertae flux and spectral variability

Author: Raiteri, C. M., Villata, M., Bruschini, L., Capetti, A., Kurtanidze, O. M., Larionov, V. M., Romano, P., Vercellone, S., Agudo, I., Aller, H. D., Aller, M. F., Arkharov, A. A., Bach, U., Berdyugin, A., Blinov, D. A., Böttcher, M., Buemi, C. S., Calcidese, P., Carosati, D., Casas, R., Chen, W. -P., Coloma, J., Diltz, C., Di Paola, A., Dolci, M., Efimova, N. V., Forné, E., Gómez, J. L., Gurwell, M. A., Hakola, A., Hovatta, T., Hsiao, H. Y., Jordan, B., Jorstad, S. G., Koptelova, E., Kurtanidze, S. O., Lähteenmäki, A., Larionova, E. G., Leto, P., Lindfors, E., Ligustri, R., Marscher, A. P., Morozova, D. A., Nikolashvili, M. G., Nilsson, K., Ros, J. A., Roustazadeh, P., Sadun, A. C., Sillanpää, A., Sainio, J., Takalo, L. O., Tornikoski, M., Trigilio, C., Troitsky, I. S., and Umana, G.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) monitored BL Lacertae in 2008-2009 at radio, near-IR, and optical frequencies. During this period, high-energy observations were performed by XMM-Newton, Swift, and Fermi. We analyse these data with particular attention to the calibration of Swift UV data, and apply a helical jet model to interpret the source broad-band variability. The GASP-WEBT observations show an optical flare in 2008 February-March, and oscillations of several tenths of mag on a few-day time scale afterwards. The radio flux is only mildly variable. The UV data from both XMM-Newton and Swift seem to confirm a UV excess that is likely caused by thermal emission from the accretion disc. The X-ray data from XMM-Newton indicate a strongly concave spectrum, as well as moderate flux variability on an hour time scale. The Swift X-ray data reveal fast (interday) flux changes, not correlated with those observed at lower energies. We compare the spectral energy distribution (SED) corresponding to the 2008 low-brightness state, which was characterised by a synchrotron dominance, to the 1997 outburst state, where the inverse-Compton emission was prevailing. A fit with an inhomogeneous helical jet model suggests that two synchrotron components are at work with their self inverse-Compton emission. Most likely, they represent the radiation from two distinct emitting regions in the jet. We show that the difference between the source SEDs in 2008 and 1997 can be explained in terms of pure geometrical variations. The outburst state occurred when the jet-emitting regions were better aligned with the line of sight, producing an increase of the Doppler beaming factor. Our analysis demonstrates that the jet geometry can play an extremely important role in the BL Lacertae flux and spectral variability., Comment: 12 pages, 10 figures, accepted for publication in A&A
Published: 2010
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26. The December 2009 gamma-ray flare of 3C 454.3: the multifrequency campaign

Author: Pacciani, L., Vittorini, V., Tavani, M., Fiocchi, M. T., Vercellone, S., D'Ammando, F., Sakamoto, T., Pian, E., Raiteri, C. M., Villata, M., Sasada, M., Itoh, R., Yamanaka, M., Uemura, M., Striani, E., Fugazza, D., Tiengo, A., Krimm, H. A., Stroh, M. C., Falcone, A. D., Curran, P. A., Sadun, A. C., Lahteenmaki, A., Tornikoski, M., Aller, H. D., Aller, M. F., Lin, C. S., Larionov, V. M., Leto, P., Takalo, L. O., Berdyugin, A., Gurwell, M. A., Bulgarelli, A., Chen, A. W., Donnarumma, I., Giuliani, A., Longo, F., Pucella, G., Argan, A., Caraveo, G. Barbiellini P., Cattaneo, P. W., Cocco, V., Costa, E., De Paris, G., Del Monte, E., Di Cocco, G., Evangelista, Y., Ferrari, A., Feroci, M., Fiorini, M., Fuschino, F., Galli, M., Gianotti, F., Labanti, C., Lapshov, I., Lazzarotto, F., Lipari, P., Marisaldi, M., Mereghetti, S., Morelli, E., Moretti, E., Morselli, A., Pellizzoni, A., Perotti, F., Piano, G., Picozza, P., Pilia, M., Prest, M., Rapisarda, M., Rappoldi, A., Rubini, A., Sabatini, S., Soffitta, P., Trifoglio, M., Trois, A., Vallazza, E., Zanello, D., Colafrancesco, S., Pittori, C., Verrecchia, F., Santolamazza, P., Lucarelli, F., Giommi, P., and Salotti, L.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: During the month of December, 2009 the blazar 3C 454.3 became the brightest gamma-ray source in the sky, reaching a peak flux F ~2000E-8 ph/cm2/s for E > 100 MeV. Starting in November, 2009 intensive multifrequency campaigns monitored the 3C 454 gamma-ray outburst. Here we report the results of a 2-month campaign involving AGILE, INTEGRAL, Swift/XRT, Swift/BAT, RossiXTE for the high-energy observations, and Swift/UVOT, KANATA, GRT, REM for the near-IR/optical/UV data. The GASP/WEBT provided radio and additional optical data. We detected a long-term active emission phase lasting ~1 month at all wavelengths: in the gamma-ray band, peak emission was reached on December 2-3, 2009. Remarkably, this gamma-ray super-flare was not accompanied by correspondingly intense emission in the optical/UV band that reached a level substantially lower than the previous observations in 2007-2008. The lack of strong simultaneous optical brightening during the super-flare and the determination of the broad-band spectral evolution severely constrain the theoretical modelling. We find that the pre- and post-flare broad-band behavior can be explained by a one-zone model involving SSC plus external Compton emission from an accretion disk and a broad-line region. However, the spectra of the Dec. 2-3, 2009 super-flare and of the secondary peak emission on Dec. 9, 2009 cannot be satisfactorily modelled by a simple one-zone model. An additional particle component is most likely active during these states., Comment: 21 pages, 2 figures, ApJL accepted
Published: 2010
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27. Multiwavelength Observations of Markarian 421 in 2005 - 2006

Author: Horan, D., Acciari, V. A., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K. L., Cannon, A., Celik, O., Cesarini, A., Chow, Y. C. K., Ciupik, L., Cogan, P., Falcone, A. D., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L. F., Gall, D., Gillanders, G. H., Grube, J., Gyuk, G., Hanna, D., Hays, E., Kertzman, M., Kildea, J., Konopelko, A., Krawczynski, H., Lang, M. J., Lee, K., Moriarty, P., Nagai, T., Niemiec, J., Ong, R. A., Perkins, J. S., Pohl, M., Quinn, J., Reynolds, P. T., Rose, H. J., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Toner, J. A., Vassiliev, V. V., Wakely, S. P., Weekes, T. C., White, R. J., Williams, D. A., Wood, M. D., Zitzer, B., Aller, H. D., Aller, M. F., Baker, M., Barnaby, D., Carini, M. T., Charlot, P., Dumm, J. P., Fields, N. E., Hovatta, T., Jordan, B., Kovalev, Y. A., Kovalev, Y. Y., Krimm, H. A., Kurtanidze, O. M., Lahteenmaki, A., Campion, J. F. Le, Maune, J., Montaruli, T., Sadun, A. C., Smith, S., Tornikoski, M., Turunen, M., and Walters, R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Since September 2005, the Whipple 10m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five Northern Hemisphere blazars that have already been detected at the Whipple Observatory, Markarian 421, H1426+428, Markarian 501, 1ES 1959+650 and 1ES 2344+514, are monitored routinely each night that they are visible. We report on the Markarian 421 observations taken from November 2005 to June 2006 in the gamma-ray, X-ray, optical and radio bands. During this time, Markarian 421 was found to be variable at all wavelengths probed. Both the variability and the correlations among different energy regimes are studied in detail here. A tentative correlation, with large spread, was measured between the X-ray and gamma-ray bands, while no clear correlation was evident among the other energy bands. In addition to this, the well-sampled spectral energy distribution of Markarian 421 (1101+384) is presented for three different activity levels. The observations of the other blazar targets will be reported separately., Comment: 58 pages, 22 Figures. Accepted for publication in ApJ
Published: 2009
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28. Results from the Blazar Monitoring Campaign at the Whipple 10m Gamma-ray Telescope

Author: Steele, David, Carini, M. T., Charlot, P., Kurtanidze, O., Lahteenmaki, A., Montaruli, T., Sadun, A. C., and Villata, M.
Subjects: Astrophysics
Abstract: In September 2005, the observing program of the Whipple 10 m gamma-ray telescope was redefined to be dedicated almost exclusively to AGN monitoring. Since then the five Northern Hemisphere blazars that had already been detected at Whipple are monitored routinely each night that they are visible. Thanks to the efforts of a large number of multiwavelength collaborators, the first year of this program has been very successful. We report here on the analysis of Markarian 421 observations taken from November, 2005 to May, 2006 in the gamma-ray, X-ray, optical and radio bands., Comment: 4 pages; contribution to the 30th International Cosmic Ray Conference, Merida, Mexico, July 2007
Published: 2007

29. Optical and radio variability of the BL Lac object AO 0235+16: a possible 5-6 year periodicity

Author: Raiteri, C. M., Villata, M., Aller, H. D., Aller, M. F., Heidt, J., Kurtanidze, O. M., Lanteri, L., Maesano, M., Massaro, E., Montagni, F., Nesci, R., Nilsson, K., Nikolashvili, M. G., Nurmi, P., Ostorero, L., Pursimo, T., Rekola, R., Sillanpaa, A., Takalo, L. O., Terasranta, H., Tosti, G., Balonek, T. J., Feldt, M., McGrath, E. J., Heines, A., Heisler, C., Hu, J., Kidger, M., Mattox, J. R., Pati, A., Robb, R., Sadun, A. C., Shastri, P., Wagner, S. J., Wei, J., and Wu, X.
Subjects: Astrophysics
Abstract: New optical and radio data on the BL Lacertae object AO 0235+16 have been collected in the last four years by a wide international collaboration, which confirm the intense activity of this source. The optical data also include the results of the Whole Earth Blazar Telescope (WEBT) first-light campaign organized in November 1997. The optical spectrum is observed to basically steepen when the source gets fainter. We have investigated the existence of typical variability time scales and of possible correlations between the optical and radio emissions by means of visual inspection, Discrete Correlation Function analysis, and Discrete Fourier Transform technique. The major radio outbursts are found to repeat quasi-regularly with a periodicity of about 5.7 years; this period is also in agreement with the occurrence of some of the major optical outbursts, but not all of them., Comment: to be published in A&A
Published: 2001
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30. X-ray Emission from the Radio Jet in 3C 120

Author: Harris, D. E., Hjorth, J., Sadun, A. C., Silverman, J. D., and Vestergaard, M.
Subjects: Astrophysics
Abstract: We report the discovery of X-ray emission from a radio knot at a projected distance of 25" from the nucleus of the Seyfert galaxy, 3C 120. The data were obtained with the ROSAT High Resolution Imager (HRI). Optical upper limits for the knot preclude a simple power law extension of the radio spectrum and we calculate some of the physical parameters for thermal bremsstrahlung and synchrotron self-Compton models. We conclude that no simple model is consistent with the data but if the knot contains small regions with flat spectra, these could produce the observed X-rays (via synchrotron emission) without being detected at other wavebands., Comment: 6 pages latex plus 3 ps/eps figures. Uses 10pt.sty and emulateapj.sty. Accepted for publication in the ApJ (6 Jan 99)
Published: 1999
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31. Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A

Author: Acharyya, A., primary, Adams, C. B., additional, Archer, A., additional, Bangale, P., additional, Bartkoske, J. T., additional, Batista, P., additional, Benbow, W., additional, Brill, A., additional, Buckley, J. H., additional, Christiansen, J. L., additional, Chromey, A. J., additional, Errando, M., additional, Falcone, A., additional, Feng, Q., additional, Foote, G. M., additional, Fortson, L., additional, Furniss, A., additional, Gallagher, G., additional, Hanlon, W., additional, Hanna, D., additional, Hervet, O., additional, Hinrichs, C. E., additional, Hoang, J., additional, Holder, J., additional, Humensky, T. B., additional, Jin, W., additional, Kaaret, P., additional, Kertzman, M., additional, Kherlakian, M., additional, Kieda, D., additional, Kleiner, T. K., additional, Korzoun, N., additional, Kumar, S., additional, Lang, M. J., additional, Lundy, M., additional, Maier, G., additional, McGrath, C. E, additional, Millard, M. J., additional, Millis, J., additional, Mooney, C. L., additional, Moriarty, P., additional, Mukherjee, R., additional, O’Brien, S., additional, Ong, R. A., additional, Pohl, M., additional, Pueschel, E., additional, Quinn, J., additional, Ragan, K., additional, Reynolds, P. T., additional, Ribeiro, D., additional, Roache, E., additional, Sadeh, I., additional, Sadun, A. C., additional, Saha, L., additional, Santander, M., additional, Sembroski, G. H., additional, Shang, R., additional, Splettstoesser, M., additional, Talluri, A. Kaushik, additional, Tucci, J. V., additional, Vassiliev, V. V., additional, Weinstein, A., additional, Williams, D. A., additional, Wong, S. L., additional, Woo, J., additional, Aharonian, F., additional, Aschersleben, J., additional, Backes, M., additional, Martins, V. Barbosa, additional, Batzofin, R., additional, Becherini, Y., additional, Berge, D., additional, Bernlöhr, K., additional, Bi, B., additional, Böttcher, M., additional, Boisson, C., additional, Bolmont, J., additional, de Bony de Lavergne, M., additional, Borowska, J., additional, Bouyahiaoui, M., additional, Bradascio, F., additional, Breuhaus, M., additional, Brose, R., additional, Brun, F., additional, Bruno, B., additional, Bulik, T., additional, Burger-Scheidlin, C., additional, Caroff, S., additional, Casanova, S., additional, Cecil, R., additional, Celic, J., additional, Cerruti, M., additional, Chand, T., additional, Chandra, S., additional, Chen, A., additional, Chibueze, J., additional, Chibueze, O., additional, Cotter, G., additional, Dai, S., additional, Mbarubucyeye, J. Damascene, additional, Djannati-Ataï, A., additional, Dmytriiev, A., additional, Doroshenko, V., additional, Einecke, S., additional, Ernenwein, J.-P., additional, de Clairfontaine, G. Fichet, additional, Filipovic, M., additional, Fontaine, G., additional, Füßling, M., additional, Funk, S., additional, Gabici, S., additional, Ghafourizadeh, S., additional, Giavitto, G., additional, Glawion, D., additional, Glicenstein, J. F., additional, Goswami, P., additional, Grolleron, G., additional, Haerer, L., additional, Hinton, J. A., additional, Holch, T. L., additional, Holler, M., additional, Horns, D., additional, Jamrozy, M., additional, Jankowsky, F., additional, Joshi, V., additional, Jung-Richardt, I., additional, Kasai, E., additional, Katarzyński, K., additional, Khatoon, R., additional, Khélifi, B., additional, Klepser, S., additional, Kluźniak, W., additional, Kosack, K., additional, Kostunin, D., additional, Lang, R. G., additional, Le Stum, S., additional, Lemière, A., additional, Lenain, J.-P., additional, Leuschner, F., additional, Lohse, T., additional, Luashvili, A., additional, Lypova, I., additional, Mackey, J., additional, Malyshev, D., additional, Marandon, V., additional, Marchegiani, P., additional, Marcowith, A., additional, Martí-Devesa, G., additional, Marx, R., additional, Mitchell, A., additional, Moderski, R., additional, Mohrmann, L., additional, Montanari, A., additional, Moulin, E., additional, Murach, T., additional, Nakashima, K., additional, Niemiec, J., additional, Noel, A. Priyana, additional, O’Brien, P., additional, Olivera-Nieto, L., additional, de Ona Wilhelmi, E., additional, Ostrowski, M., additional, Panny, S., additional, Panter, M., additional, Peron, G., additional, Prokhorov, D. A., additional, Pühlhofer, G., additional, Punch, M., additional, Quirrenbach, A., additional, Reichherzer, P., additional, Reimer, A., additional, Reimer, O., additional, Ren, H., additional, Renaud, M., additional, Rieger, F., additional, Rudak, B., additional, Ruiz-Velasco, E., additional, Sahakian, V., additional, Santangelo, A., additional, Sasaki, M., additional, Schäfer, J., additional, Schüssler, F., additional, Schutte, H. M., additional, Schwanke, U., additional, Shapopi, J. N. S., additional, Specovius, A., additional, Spencer, S., additional, Stawarz, Ł., additional, Steenkamp, R., additional, Steinmassl, S., additional, Sushch, I., additional, Suzuki, H., additional, Takahashi, T., additional, Tanaka, T., additional, Terrier, R., additional, van Eldik, C., additional, Vecchi, M., additional, Veh, J., additional, Venter, C., additional, Vink, J., additional, White, R., additional, Wierzcholska, A., additional, Wong, Yu Wun, additional, Zacharias, M., additional, Zargaryan, D., additional, Zdziarski, A. A., additional, Zech, A., additional, Zouari, S., additional, Żywucka, N., additional, and Mori, K., additional
Published: 2023
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32. Multi-wavelength Observations of a Long-duration Flare from BL Lacertae

Author: Hinrichs, Claire E., primary, Acharyya, Atreya, additional, and Sadun, Alberto C., additional
Published: 2023
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33. Exploring the Potential of the Pulsed Laser onboard the CALIPSO Satellite to Improve Calibration with VERITAS

Author: Foote, Gregory M, primary, Acharyya, Atreya, additional, Adams, Colin, additional, Archer, Avery, additional, Bangale, Priyadarshini, additional, Bartkoske, Joshua, additional, Batista, Pedro Ivo, additional, Benbow, Wystan, additional, Christiansen, Jodi, additional, Chromey, Alisha, additional, Duerr, Anne, additional, Errando, Manel, additional, Feng, Qi, additional, Fortson, Lucy, additional, Furniss, Amy, additional, Hanlon, William, additional, Hervet, Olivier, additional, Hinrichs, Claire E., additional, Hoang, John, additional, Holder, Jamie, additional, Hughes, Zachary, additional, Humensky, Thomas Brian, additional, Jin, Weidong, additional, Johnson, Madalyn, additional, Kertzman, Mary, additional, Kherlakian, Maria, additional, Kieda, David, additional, Kleiner, Tobias Kai, additional, Korzoun, Nikolas, additional, Kumar, Sajan, additional, Lang, Mark, additional, Lundy, Matthew, additional, Maier, Gernot, additional, McGrath, Conor, additional, Millard, Matthew, additional, Mooney, Connor L, additional, Moriarty, Patrick, additional, Mukherjee, Reshmi, additional, O'Brien, Stephan, additional, Ong, Rene, additional, Park, Nahee, additional, Poggemann, Connor, additional, Pohl, Martin, additional, Pueschel, Elisa, additional, Quinn, John, additional, Rabinowitz, Pazit, additional, Ragan, Ken, additional, Reynolds, Paul, additional, Ribeiro, Deivid, additional, Roache, Emmet, additional, Ryan, James, additional, Sadeh, Iftach, additional, Sadun, Alberto C., additional, Saha, Lab, additional, Santander, Marcos, additional, Sembroski, Glenn, additional, Shang, Ruo-Yu, additional, Splettstoesser, Megan, additional, Talluri, Anjana, additional, Tucci, James, additional, Vassiliev, Vladimir, additional, Weinstein, Amanda, additional, Williams, David A., additional, Wong, Samantha, additional, and Woo, Jooyun, additional
Published: 2023
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34. Investigating Possible Correlations between Gamma-Ray and Optical Lightcurves for TeV-Detected Northern Blazars over 8 Years of Observations

Author: Acharyya, Atreya, primary and Sadun, Alberto C., additional
Published: 2023
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35. Multimessenger Characterization of Markarian 501 during Historically Low X-Ray and γ-Ray Activity

Author: Abe, H., primary, Abe, S., additional, Acciari, V. A., additional, Agudo, I., additional, Aniello, T., additional, Ansoldi, S., additional, Antonelli, L. A., additional, Arbet-Engels, A., additional, Arcaro, C., additional, Artero, M., additional, Asano, K., additional, Baack, D., additional, Babić, A., additional, Baquero, A., additional, de Almeida, U. Barres, additional, Barrio, J. A., additional, Batković, I., additional, Baxter, J., additional, Becerra González, J., additional, Bednarek, W., additional, Bernardini, E., additional, Bernardos, M., additional, Berti, A., additional, Besenrieder, J., additional, Bhattacharyya, W., additional, Bigongiari, C., additional, Biland, A., additional, Blanch, O., additional, Bonnoli, G., additional, Bošnjak, Ž., additional, Burelli, I., additional, Busetto, G., additional, Carosi, R., additional, Carretero-Castrillo, M., additional, Castro-Tirado, A. J., additional, Ceribella, G., additional, Chai, Y., additional, Chilingarian, A., additional, Cikota, S., additional, Colombo, E., additional, Contreras, J. L., additional, Cortina, J., additional, Covino, S., additional, D’Amico, G., additional, D’Elia, V., additional, Da Vela, P., additional, Dazzi, F., additional, De Angelis, A., additional, De Lotto, B., additional, Del Popolo, A., additional, Delfino, M., additional, Delgado, J., additional, Delgado Mendez, C., additional, Depaoli, D., additional, Di Pierro, F., additional, Di Venere, L., additional, Souto Espiñeira, E. Do, additional, Dominis Prester, D., additional, Donini, A., additional, Dorner, D., additional, Doro, M., additional, Elsaesser, D., additional, Emery, G., additional, Escudero, J., additional, Fallah Ramazani, V., additional, Fariña, L., additional, Fattorini, A., additional, Foffano, L., additional, Font, L., additional, Fruck, C., additional, Fukami, S., additional, Fukazawa, Y., additional, García López, R. J., additional, Garczarczyk, M., additional, Gasparyan, S., additional, Gaug, M., additional, Giesbrecht Paiva, J. G., additional, Giglietto, N., additional, Giordano, F., additional, Gliwny, P., additional, Godinović, N., additional, Grau, R., additional, Green, D., additional, Green, J. G., additional, Hadasch, D., additional, Hahn, A., additional, Hassan, T., additional, Heckmann, L., additional, Herrera, J., additional, Hrupec, D., additional, Hütten, M., additional, Imazawa, R., additional, Inada, T., additional, Iotov, R., additional, Ishio, K., additional, Jiménez Martínez, I., additional, Jormanainen, J., additional, Kerszberg, D., additional, Kobayashi, Y., additional, Kubo, H., additional, Kushida, J., additional, Lamastra, A., additional, Lelas, D., additional, Leone, F., additional, Lindfors, E., additional, Linhoff, L., additional, Lombardi, S., additional, Longo, F., additional, López-Coto, R., additional, López-Moya, M., additional, López-Oramas, A., additional, Loporchio, S., additional, Lorini, A., additional, Lyard, E., additional, Machado de Oliveira Fraga, B., additional, Majumdar, P., additional, Makariev, M., additional, Maneva, G., additional, Mang, N., additional, Manganaro, M., additional, Mangano, S., additional, Mannheim, K., additional, Mariotti, M., additional, Martínez, M., additional, Mas-Aguilar, A., additional, Mazin, D., additional, Menchiari, S., additional, Mender, S., additional, Mićanović, S., additional, Miceli, D., additional, Miener, T., additional, Miranda, J. M., additional, Mirzoyan, R., additional, Molina, E., additional, Mondal, H. A., additional, Moralejo, A., additional, Morcuende, D., additional, Moreno, V., additional, Nakamori, T., additional, Nanci, C., additional, Nava, L., additional, Neustroev, V., additional, Nievas Rosillo, M., additional, Nigro, C., additional, Nilsson, K., additional, Nishijima, K., additional, Njoh Ekoume, T., additional, Noda, K., additional, Nozaki, S., additional, Ohtani, Y., additional, Oka, T., additional, Okumura, A., additional, Otero-Santos, J., additional, Paiano, S., additional, Palatiello, M., additional, Paneque, D., additional, Paoletti, R., additional, Paredes, J. M., additional, Pavletić, L., additional, Persic, M., additional, Pihet, M., additional, Pirola, G., additional, Podobnik, F., additional, Moroni, P. G. Prada, additional, Prandini, E., additional, Principe, G., additional, Priyadarshi, C., additional, Rhode, W., additional, Ribó, M., additional, Rico, J., additional, Righi, C., additional, Rugliancich, A., additional, Sahakyan, N., additional, Saito, T., additional, Sakurai, S., additional, Satalecka, K., additional, Saturni, F. G., additional, Schleicher, B., additional, Schmidt, K., additional, Schmuckermaier, F., additional, Schubert, J. L., additional, Schweizer, T., additional, Sitarek, J., additional, Sliusar, V., additional, Sobczynska, D., additional, Spolon, A., additional, Stamerra, A., additional, Strišković, J., additional, Strom, D., additional, Strzys, M., additional, Suda, Y., additional, Surić, T., additional, Tajima, H., additional, Takahashi, M., additional, Takeishi, R., additional, Tavecchio, F., additional, Temnikov, P., additional, Terauchi, K., additional, Terzić, T., additional, Teshima, M., additional, Tosti, L., additional, Truzzi, S., additional, Tutone, A., additional, Ubach, S., additional, van Scherpenberg, J., additional, Acosta, M. Vazquez, additional, Ventura, S., additional, Verguilov, V., additional, Viale, I., additional, Vigorito, C. F., additional, Vitale, V., additional, Vovk, I., additional, Walter, R., additional, Will, M., additional, Wunderlich, C., additional, Yamamoto, T., additional, Zarić, D., additional, Cerruti, M., additional, Acosta-Pulido, J. A., additional, Apolonio, G., additional, Bachev, R., additional, Baloković, M., additional, Benítez, E., additional, Björklund, I., additional, Bozhilov, V., additional, Brown, L. F., additional, Bugg, A., additional, Carbonell, W., additional, Carnerero, M. I., additional, Carosati, D., additional, Casadio, C., additional, Chamani, W., additional, Chen, W. P., additional, Chigladze, R. A., additional, Damljanovic, G., additional, Epps, K., additional, Erkenov, A., additional, Feige, M., additional, Finke, J., additional, Fuentes, A., additional, Gazeas, K., additional, Giroletti, M., additional, Grishina, T. S., additional, Gupta, A. C., additional, Gurwell,, M. A., additional, Heidemann, E., additional, Hiriart, D., additional, Hou, W. J., additional, Hovatta, T., additional, Ibryamov, S., additional, Joner, M. D., additional, Jorstad, S. G., additional, Kania, J., additional, Kiehlmann, S., additional, Kimeridze, G. N., additional, Kopatskaya, E. N., additional, Kopp, M., additional, Korte, M., additional, Kotas, B., additional, Koyama, S., additional, Kramer, J. A., additional, Kunkel, L., additional, Kurtanidze, S. O., additional, Kurtanidze, O. M., additional, Lähteenmäki, A., additional, López, J. M., additional, Larionov, V. M., additional, Larionova, E. G., additional, Larionova, L. V., additional, Leto, C., additional, Lorey, C., additional, Mújica, R., additional, Madejski, G. M., additional, Marchili, N., additional, Marscher, A. P., additional, Minev, M., additional, Modaressi, A., additional, Morozova, D. A., additional, Mufakharov, T., additional, Myserlis, I., additional, Nikiforova, A. A., additional, Nikolashvili, M. G., additional, Ovcharov, E., additional, Perri, M., additional, Raiteri, C. M., additional, Readhead, A. C. S., additional, Reimer, A., additional, Reinhart, D., additional, Righini, S., additional, Rosenlehner, K., additional, Sadun, A. C., additional, Savchenko, S. S., additional, Scherbantin, A., additional, Schneider, L., additional, Schoch, K., additional, Seifert, D., additional, Semkov, E., additional, Sigua, L. A., additional, Singh, C., additional, Sola, P., additional, Sotnikova, Y., additional, Spencer, M., additional, Steineke, R., additional, Stojanovic, M., additional, Strigachev, A., additional, Tornikoski, M., additional, Traianou, E., additional, Tramacere, A., additional, Troitskaya, Yu. V., additional, Troitskiy, I. S., additional, Trump, J. B., additional, Tsai, A., additional, Valcheva, A., additional, Vasilyev, A. A., additional, Verrecchia, F., additional, Villata, M., additional, Vince, O., additional, Vrontaki, K., additional, Weaver, Z. R., additional, Zaharieva, E., additional, and Zottmann, N., additional
Published: 2023
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36. VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations

Author: Acharyya, A., primary, Adams, C. B., additional, Archer, A., additional, Bangale, P., additional, Benbow, W., additional, Brill, A., additional, Christiansen, J. L., additional, Chromey, A. J., additional, Errando, M., additional, Falcone, A., additional, Feng, Q., additional, Finley, J. P., additional, Foote, G. M., additional, Fortson, L., additional, Furniss, A., additional, Gallagher, G., additional, Hanlon, W., additional, Hanna, D., additional, Hervet, O., additional, Hinrichs, C. E., additional, Hoang, J., additional, Holder, J., additional, Jin, W., additional, Johnson, M. N., additional, Kaaret, P., additional, Kertzman, M., additional, Kieda, D., additional, Kleiner, T. K., additional, Korzoun, N., additional, Krennrich, F., additional, Lang, M. J., additional, Lundy, M., additional, Maier, G., additional, McGrath, C. E, additional, Millard, M. J., additional, Millis, J., additional, Mooney, C. L., additional, Moriarty, P., additional, Mukherjee, R., additional, O’Brien, S., additional, Ong, R. A., additional, Pohl, M., additional, Pueschel, E., additional, Quinn, J., additional, Ragan, K., additional, Reynolds, P. T., additional, Ribeiro, D., additional, Roache, E., additional, Sadeh, I., additional, Sadun, A. C., additional, Saha, L., additional, Santander, M., additional, Sembroski, G. H., additional, Shang, R., additional, Splettstoesser, M., additional, Talluri, A. K., additional, Tucci, J. V., additional, Vassiliev, V. V., additional, Williams, D. A., additional, Wong, S. L., additional, Hovatta, Talvikki, additional, Jorstad, Svetlana G., additional, Kiehlmann, Sebastian, additional, Lähteenmäki, Anne, additional, Liodakis, Ioannis, additional, Marscher, Alan P., additional, Max-Moerbeck, Walter, additional, Readhead, Anthony C. S., additional, Reeves, Rodrigo, additional, Smith, Paul S., additional, and Tornikoski, Merja, additional
Published: 2023
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37. VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations

Author: Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Benbow, W., Brill, A., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Foote, G. M., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W., Hanna, D., Hervet, O., Hinrichs, C. E., Hoang, J., Holder, J., Jin, W., Johnson, M. N., Kaaret, P., Kertzman, M., Kieda, D., Kleiner, T. K., Korzoun, N., Krennrich, F., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E., Millard, M. J., Millis, J., Mooney, C. L., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Sadeh, I., Sadun, A. C., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Talluri, A. Kaushik, Tucci, J. V., Vassiliev, V. V., Williams, D. A., Wong, S. L., Hovatta, Talvikki, Jorstad, Svetlana G., Kiehlmann, Sebastian, Lähteenmäki, Anne, Liodakis, Ioannis, Marscher, Alan P., Max-Moerbeck, Walter, Readhead, Anthony C. S., Reeves, Rodrigo, Smith, Paul S., Tornikoski, Merja, and VERITAS Collaboration
Subjects: VHE [gamma ray], model [emission], FOS: Physical sciences, GeV, power spectrum, GLAST, emission: model, blazar, emission [gamma ray], synchrotron, flux [gamma ray], optical, gamma ray: flux, High Energy Astrophysical Phenomena (astro-ph.HE), variability, imaging [detector], photon, detector: imaging, polarization: monitoring, monitoring [polarization], gamma ray: emission, gamma ray: VHE, correlation, ddc:520, spectral, VERITAS, Astrophysics - High Energy Astrophysical Phenomena, spectral energy distribution
Abstract: The astrophysical journal / 1 950(2), 152 (2023). doi:10.3847/1538-4357/acd2d0, We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13σ detection with a differential photon spectral index, Γ = 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of τ$_{obs}$ = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model., Published by Institute of Physics Publ., London
Published: 2023
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38. Blazar spectral variability as explained by a twisted inhomogeneous jet

Author: Raiteri, C. M., Villata, M., Acosta-Pulido, J. A., Agudo, I., Arkharov, A. A., Bachev, R., Baida, G. V., Benítez, E., Borman, G. A., Boschin, W., Bozhilov, V., Butuzova, M. S., Calcidese, P., Carnerero, M. I., Carosati, D., Casadio, C., Castro-Segura, N., Chen, W.-P., Damljanovic, G., DʼAmmando, F., Di Paola, A., Echevarría, J., Efimova, N. V., Ehgamberdiev, Sh. A., Espinosa, C., Fuentes, A., Giunta, A., Gómez, J. L., Grishina, T. S., Gurwell, M. A., Hiriart, D., Jermak, H., Jordan, B., Jorstad, S. G., Joshi, M., Kopatskaya, E. N., Kuratov, K., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Larionov, V. M., Larionova, E. G., Larionova, L. V., Lázaro, C., Lin, C. S., Malmrose, M. P., Marscher, A. P., Matsumoto, K., McBreen, B., Michel, R., Mihov, B., Minev, M., Mirzaqulov, D. O., Mokrushina, A. A., Molina, S. N., Moody, J. W., Morozova, D. A., Nazarov, S. V., Nikolashvili, M. G., Ohlert, J. M., Okhmat, D. N., Ovcharov, E., Pinna, F., Polakis, T. A., Protasio, C., Pursimo, T., Redondo-Lorenzo, F. J., Rizzi, N., Rodriguez-Coira, G., Sadakane, K., Sadun, A. C., Samal, M. R., Savchenko, S. S., Semkov, E., Skiff, B. A., Slavcheva-Mihova, L., Smith, P. S., Steele, I. A., Strigachev, A., Tammi, J., Thum, C., Tornikoski, M., Troitskaya, Yu. V., Troitsky, I. S., Vasilyev, A. A., and Vince, O.
Published: 2017
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39. Multiwavelength Observations of the Blazar VER J0521+211 during an Elevated TeV Gamma-Ray State

Author: Abe, H., Abe, S., Acciari, V. A., Agudo, I., Aniello, T., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Arcaro, C., Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., Barres de Almeida, U., Barrio, J. A., Batković, I., Baxter, J., Becerra González, J., Bednarek, W., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bošnjak, Ž., Burelli, I., Busetto, G., Carosi, R., Carretero-Castrillo, M., Castro-Tirado, A. J., Ceribella, G., Chai, Y., Chilingarian, A., Cikota, S., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Del Popolo, A., Delfino, M., Delgado, J., Delgado Mendez, C., Depaoli, D., Di Pierro, F., Di Venere, L., Do Souto Espiñeira, E., Dominis Prester, D., Donini, A., Dorner, D., Doro, M., Elsaesser, D., Emery, G., Escudero, J., Fallah Ramazani, V., Fariña, L., Fattorini, A., Foffano, L., Font, L., Fruck, C., Fukami, S., Fukazawa, Y., García López, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Giesbrecht Paiva, J. G., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Grau, R., Green, D., Green, J. G., Hadasch, D., Hahn, A., Hassan, T., Heckmann, L., Herrera, J., Hrupec, D., Hütten, M., Imazawa, R., Inada, T., Iotov, R., Ishio, K., Jiménez Martínez, I., Jormanainen, J., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Linhoff, L., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Lorini, A., Lyard, E., Machado de Oliveira Fraga, B., Majumdar, P., Makariev, M., Maneva, G., Mang, N., Manganaro, M., Mangano, S., Mannheim, K., Mariotti, M., Martínez, M., Mas-Aguilar, A., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., Molina, E., Mondal, H. A., Moralejo, A., Morcuende, D., Moreno, V., Nakamori, T., Nanci, C., Nava, L., Neustroev, V., Nievas Rosillo, M., Nigro, C., Nilsson, K., Nishijima, K., Njoh Ekoume, T., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Okumura, A., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Persic, M., Pihet, M., Pirola, G., Podobnik, F., Prada Moroni, P. G., Prandini, E., Principe, G., Priyadarshi, C., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schmuckermaier, F., Schubert, J. L., Schweizer, T., Sitarek, J., Sliusar, V., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Surić, T., Tajima, H., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terauchi, K., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Vazquez Acosta, M., Ventura, S., Verguilov, V., Viale, I., Vigorito, C. F., Vitale, V., Vovk, I., Walter, R., Will, M., Wunderlich, C., Yamamoto, T., Zarić, D., Other, Groups, Cerruti, collaborations: M., Acosta-Pulido, J. A., Apolonio, G., Bachev, R., Baloković, M., Benítez, E., Björklund, I., Bozhilov, V., Brown, L. F., Bugg, A., Carbonell, W., Carnerero, M. I., Carosati, D., Casadio, C., Chamani, W., Chen, W. P., Chigladze, R. A., Damljanovic, G., Epps, K., Erkenov, A., Feige, M., Finke, J., Fuentes, A., Gazeas, K., Giroletti, M., Grishina, T. S., Gupta, A. C., Gurwell, M. A., Heidemann, E., Hiriart, D., Hou, W. J., Hovatta, T., Ibryamov, S., Joner, M. D., Jorstad, S. G., Kania, J., Kiehlmann, S., Kimeridze, G. N., Kopatskaya, E. N., Kopp, M., Korte, M., Kotas, B., Koyama, S., Kramer, J. A., Kunkel, L., Kurtanidze, S. O., Kurtanidze, O. M., Lähteenmäki, A., López, J. M., Larionov, V. M., Larionova, E. G., Larionova, L. V., Leto, C., Lorey, C., Mújica, R., Madejski, G. M., Marchili, N., Marscher, A. P., Minev, M., Modaressi, A., Morozova, D. A., Mufakharov, T., Myserlis, I., Nikiforova, A. A., Nikolashvili, M. G., Ovcharov, E., Perri, M., Raiteri, C. M., Readhead, A. C. S., Reimer, A., Reinhart, D., Righini, S., Rosenlehner, K., Sadun, A. C., Savchenko, S. S., Scherbantin, A., Schneider, L., Schoch, K., Seifert, D., Semkov, E., Sigua, L. A., Singh, C., Sola, P., Sotnikova, Y., Spencer, M., Steineke, R., Stojanovic, M., Strigachev, A., Tornikoski, M., Traianou, E., Tramacere, A., Troitskaya, Yu. V., Troitskiy, I. S., Trump, J. B., Tsai, A., Valcheva, A., Vasilyev, A. A., Verrecchia, F., Villata, M., Vince, O., Vrontaki, K., Weaver, Z. R., Zaharieva, E., Zottmann, N., Ministerio de Ciencia e Innovación (España), European Commission, Federal Ministry of Education and Research (Germany), Istituto Nazionale di Fisica Nucleare, Istituto Nazionale di Astrofisica, Swiss National Science Foundation, Department of Atomic Energy (India), Ministry of Education, Culture, Sports, Science and Technology (Japan), Ministry of Education and Science (Bulgaria), and Academy of Finland
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), BL Lacertae objects: individual (VER J0521+211 = RGB J0521.8+2112) – galaxies: active – galaxies: jets – gamma rays: galaxies – radiation mechanisms: non-thermal, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Active galactic nuclei, High energy astrophysics, Blazars, BL Lacertae objects, Relativistic jets, Gamma-rays, Non-thermal radiation sources, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ddc:520, Física nuclear, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Full list of authors: Adams, C. B.; Batista, P.; Benbow, W.; Brill, A.; Brose, R.; Buckley, J. H.; Capasso, M.; Christiansen, J. L.; Errando, M.; Feng, Q.; Finley, J. P.; Foote, G. M.; Fortson, L.; Furniss, A.; Gallagher, G.; Gent, A.; Giuri, C.; Hanlon, W. F.; Hanna, D.; Hassan, T.; Hervet, O.; Holder, J.; Hona, B.; Hughes, G.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kieda, D.; Kleiner, T. K.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nievas-Rosillo, M.; Ong, R. A.; Otte, A. N.; Patel, S.; Patel, S. R.; Pfrang, K.; Pohl, M.; Prado, R. R.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Roache, E.; Ryan, J. L.; Sadeh, I; Santander, M.; Sembroski, G. H.; Shang, R.; Stevenson, B.; Tucci, J., V; Vassiliev, V. V.; Wakely, S. P.; Weinstein, A.; Wells, R. M.; Williams, D. A.; Williamson, T. J.; Acciari, V. A.; Aniello, T.; Ansoldi, S.; Antonelli, L. A.; Engels, A. Arbet; Arcaro, C.; Artero, M.; Asano, K.; Baack, D.; Babic, A.; Baquero, A.; de Almeida, U. Barres; Barrio, J. A.; Batkovic, I; Becerra Gonzalez, J.; Bednarek, W.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bokenkamp, H.; Bonnoli, G.; Bosnjak, Z.; Burelli, I; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Del Popolo, A.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Di Pierro, F.; Di Venere, L.; Do Souto Espineira, E.; Prester, D. Dominis; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Ramazani, V. Fallah; Farina, L.; Fattorini, A.; Font, L.; Fruck, C.; Fukami, S.; Fukazawa, Y.; Garcia Lopez, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinovic, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Heckmann, L.; Herrera, J.; Hrupec, D.; Hutten, M.; Inada, T.; Iotov, R.; Ishio, K.; Iwamura, Y.; Jimenez Martinez, I; Jormanainen, J.; Jouvin, L.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Linhoff, L.; Lombardi, S.; Longo, F.; Lopez-Coto, R.; Lopez-Moya, M.; Lopez-Oramas, A.; Loporchio, S.; Lorini, A.; de Oliveira Fraga, B. Machado; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Mariotti, M.; Martinez, M.; Aguilar, A. Mas; Mazin, D.; Menchiari, S.; Mender, S.; Micanovic, S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Mondal, H. A.; Moralejo, A.; Morcuende, D.; Moreno, V; Nakamori, T.; Nanci, C.; Nava, L.; Neustroev, V; Nievas Rosillo, M.; Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pavletic, L.; Penil, P.; Persic, M.; Pihet, M.; Moroni, P. G. Prada; Prandini, E.; Priyadarshi, C.; Puljak, I; Rhode, W.; Ribo, M.; Rico, J.; Righi, C.; Rugliancich, A.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schmuckermaier, F.; Schubert, J. L.; Schweizer, T.; Sitarek, J.; Snidaric, I; Sobczynska, D.; Spolon, A.; Stamerra, A.; Striskovic, J.; Strom, D.; Strzys, M.; Suda, Y.; Suric, T.; Takahashi, M.; Takeishi, R.; Tavecchio, F.; Temnikov, P.; Terzic, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Viale, I; Vigorito, C. F.; Vitale, V.; Vovk, I; Will, M.; Wunderlich, C.; Yamamoto, T.; Zaric, D.; VERITAS Collaboration; MAGIC Collaboration.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We report on a long-lasting, elevated gamma-ray flux state from VER J0521+211 observed by VERITAS, MAGIC, and Fermi-LAT in 2013 and 2014. The peak integral flux above 200 GeV measured with the nightly binned light curve is (8.8 ± 0.4) × 10−7 photons m−2 s−1, or ∼37% of the Crab Nebula flux. Multiwavelength observations from X-ray, UV, and optical instruments are also presented. A moderate correlation between the X-ray and TeV gamma-ray fluxes was observed, and the X-ray spectrum appeared harder when the flux was higher. Using the gamma-ray spectrum and four models of the extragalactic background light (EBL), a conservative 95% confidence upper limit on the redshift of the source was found to be z ≤ 0.31. Unlike the gamma-ray and X-ray bands, the optical flux did not increase significantly during the studied period compared to the archival low-state flux. The spectral variability from optical to X-ray bands suggests that the synchrotron peak of the spectral energy distribution (SED) may become broader during flaring states, which can be adequately described with a one-zone synchrotron self-Compton model varying the high-energy end of the underlying particle spectrum. The synchrotron peak frequency of the SED and the radio morphology of the jet from the MOJAVE program are consistent with the source being an intermediate-frequency-peaked BL Lac object. © 2022. The Author(s). Published by the American Astronomical Society., This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, and the Smithsonian Institution in the U.S.; by NSERC in Canada; and by the Helmholtz Association in Germany. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy's Office of Science, and resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under contract No. DE-AC02-05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument. The MAGIC Collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF, MPG, and HGF; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish Ministerio de Ciencia e Innovación (MICINN) (PID2019-104114RB-C31, PID2019-104114RB-C32, PID2019-104114RB-C33, PID2019-105510GB-C31,PID2019-107847RB-C41, PID2019-107847RB-C42, PID2019-107847RB-C44, PID2019-107988GB-C22); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-400/18.12.2020; and the Academy of Finland grant No. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia "Severo Ochoa" (SEV-2016-0588, SEV-2017-0709, CEX2019-000920-S), the Unidad de Excelencia "María de Maeztu" (CEX2019-000918-M, MDM-2015-0509-18-2), and the CERCA program of the Generalitat de Catalunya; by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project uniri-prirod-18-48; by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3; by the Polish National Research Centre grant UMO-2016/22/M/ST9/00382; and by the Brazilian MCTIC, CNPq, and FAPERJ. Q.F. was supported by NSF grant PHY-1806554 at Barnard College.
Published: 2022
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40. Unveiling the complex correlation patterns in Mrk 421

Author: Arbet-Engels, A., Paneque, D., Heckmann, L., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., Barres Almeida, U., Barrio, J. A., Batković, I., Becerra González, J., Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bökenkamp, H., Bonnoli, G., Bošnjak, Ž, Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Giacomo D'Amico, D Elia, V., Da Vela, P., Dazzi, F., Angelis, A., Lotto, B., Delfino, M., Delgado, J., Delgado Mendez, C., Depaoli, D., Di Pierro, F., Di Venere, L., Do Souto Espiñeira, E., Dominis Prester, D., Donini, A., Dorner, D., Doro, M., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Fukazawa, Y., García López, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Inada, T., Ishio, K., Iwamura, Y., Jiménez Martínez, I., Jormanainen, J., Jouvin, L., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Linhoff, L., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Machado Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Nakamori, T., Nava, L., Neustroev, V., Nigro, C., Nilsson, K., Nishijima, K., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Paiano, S., Palatiello, M., Paoletti, R., Paredes, J. M., Pavletić, L., Peñil, P., Persic, M., Pihet, M., Prada Moroni, P. G., Prandini, E., Priyadarshi, C., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Surić, T., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Wunderlich, C., Yamamoto, T., Zarić, D., Balbo, M., Bretz, T., Buss, J., Eisenberger, L., Hildebrand, D., Iotov, R., Kalenski, A., D Ammando, F., Horan, D., Lien, A. Y., Baloković, M., Madejski, G. M., Perri, M., Verrecchia, F., Leto, C., Lähteenmäki, A., Tornikoski, M., Ramakrishnan, V., Järvelä, E., Vera, R. J. C., Villata, M., Raiteri, C. M., Gupta, A. C., Pandey, A., Fuentes, A., Agudo, I., Casadio, C., Semkov, E., Ibryamov, S., Marchini, A., Bachev, R., Strigachev, A., Ovcharov, E., Bozhilov, V., Valcheva, A., Zaharieva, E., Damljanovic, G., Vince, O., Larionov, V. M., Borman, G. A., Grishina, T. S., Hagen-Thorn, V. A., Kopatskaya, E. N., Larionova, E. G., Larionova, L. V., Morozova, D. A., Nikiforova, A. A., Savchenko, S. S., Troitskiy, I. S., Troitskaya, Y. V., Vasilyev, A. A., Merkulova, O. A., Chen, W. P., Samal, M., Lin, H. C., Moody, J. W., Sadun, A. C., Jorstad, S. G., Marscher, A. P., Weaver, Z. R., Feige, M., Kania, J., Kopp, M., Kunkel, L., Reinhart, D., Scherbantin, A., Schneider, L., Lorey, C., Acosta-Pulido, J. A., Carnerero, M. I., Carosati, D., Kurtanidze, S. O., Kurtanidze, O. M., Nikolashvili, M. G., Chanishvili, R. G., Chigladze, R. A., Ivanidze, R. Z., Kimeridze, G. N., Sigua, L. A., Joner, M. D., Spencer, M., Giroletti, M., Marchili, N., Righini, S., and Rizzi, N.
Subjects: Physics, education.field_of_study, Astrophysics::High Energy Astrophysical Phenomena, Population, Flux, Sigma, Astrophysics, Synchrotron, Redshift, law.invention, law, MAGIC (telescope), education, Blazar, Flare
Abstract: The blazar Mrk421 (redshift z=0.031) is one of the brightest and closest BL Lac type objects, making it an ideal target to probe blazar physics. We report on an extensive multi-wavelength observing campaign in 2017, during which the intra-band correlation patterns show some disparity and complex behaviours. Observations from several instruments are used to achieve an optimal temporal coverage from radio to TeV energies. In particular, four multi-hour NuSTAR observations organised simultaneously with MAGIC allow to obtain a precise measurement of the falling segments of the two spectral components. A detailed investigation of the very-high-energy (VHE; >100 GeV) versus X-ray flux correlation is performed, by binning the data into several sub-energy bands. A positively correlated variability is observed, but the correlation characteristics change substantially across the various bands probed. Furthermore, during the simultaneous MAGIC and NuSTAR observations a clear change of the Compton dominance is detected without a simultaneous change in the synchrotron regime, indicating "orphan gamma-ray activity". We also investigate an intriguing bright flare at VHE without a substantial flux increase in the X-rays. Within a leptonic scenario, this behaviour is best explained by the appearance of a second population of highly-energetic electrons spanning a narrow range of energies. Finally, our multi-wavelength correlation study also reveals an anti-correlation between the UV/optical and X-ray bands at a significance level above 3 sigma.
Published: 2022

41. The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies

Author: Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Dumm, J., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., Nievas-Rosillo, M., O’Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Stevenson, B., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babić, A., Banerjee, B., Barres de Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Chai, Y., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D’Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Do Souto Espiñera, E., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Fernández-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., García López, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Godinović, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Machado de Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Nöthe, M., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peñil, P., Peresano, M., Persic, M., Prada Moroni, P. G., Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Sun, S., Surić, T., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Tsujimoto, S., van Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Vovk, I., Will, M., Zarić, D., Aller, H. D., Aller, M. F., Carini, M. T., Horan, D., Jordan, B., Jorstad, S. G., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Larionov, V. M., Larionova, E. G., Madejski, G., Marscher, A. P., Max-Moerbeck, W., Moody, J. Ward, Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Sigua, L. A., Smith, P. S., Talvikki, H., Tammi, J., Tornikoski, M., Troitsky, I. S., Villata, M., (VERITAS Collaboration), (MAGIC Collaboration), (Multiwavelength Partners), Department of Energy (US), Smithsonian Institution, National Science Foundation (US), National Energy Research Scientific Computing Center (US), German Research Foundation, Istituto Nazionale di Fisica Nucleare, Istituto Nazionale di Astrofisica, Ministerio de Economía y Competitividad (España), Department of Atomic Energy (India), Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology (Japan), Croatian Science Foundation, University of Rijeka, Polish National Agency for Academic Exchange, National Aeronautics and Space Administration (US), Shota Rustaveli National Science Foundation, Boston University, University of Utah, Harvard University, University of California Los Angeles, Columbia University, University of Potsdam, Washington University St. Louis, California Polytechnic State University, San Luis Obispo, Iowa State University, University of Minnesota Twin Cities, Pennsylvania State University, Purdue University, California State University, East Bay, Georgia Institute of Technology, National University of Ireland, Galway, German Electron Synchrotron, University of California Santa Cruz, University of Delaware, University of Iowa, DePauw University, McGill University, Complutense University, University College Dublin, University of Wisconsin-Madison, Universidad de Buenos Aires, Cork Institute of Technology, University of Alabama, University of Chicago, Instituto de Astrofísica de Canarias, University of Udine, INAF, Osservatorio Astronomico di Roma, Swiss Federal Institute of Technology Zurich, Dortmund University, Saha Institute of Nuclear Physics, Centro Brasileiro de Pesquisas Físicas, University of Łódź, University of Siena, National Institute for Nuclear Physics, Max Planck Institute for Physics, Institute for High Energy Physics, University of Padova, University of Pisa, University of Würzburg, University of Turku, Autonomous University of Barcelona, University of Barcelona, National Academy of Sciences of the Republic of Armenia, The University of Tokyo, Bulgarian Academy of Sciences, Fudan University, University of Michigan, Ann Arbor, Western Kentucky University, CNRS, Dublin Institute for Advanced Studies, Ilia State University, Department of Electronics and Nanoengineering, St. Petersburg State University, United States Department of Energy, Universidad de Chile, Brigham Young University, California Institute of Technology, University of Colorado Denver, Aoyama Gakuin University, University of Arizona, Metsähovi Radio Observatory, Aalto-yliopisto, Aalto University, Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Dumm, J., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Stevenson, B., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babic, A., Banerjee, B., Barres De Almeida, U., Barrio, J. A., Becerra Gonzalez, J., Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Chai, Y., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Do Souto Espiñera, E., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Fernandez-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., Garcia Lopez, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Godinovic, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Machado De Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Masuda, S., Mazin, D., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogues, L., Nothe, M., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peñil, P., Peresano, M., Persic, M., Prada Moroni, P. G., Prandini, E., Puljak, I., Rhode, W., Ribo, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Snidaric, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Sun, S., Suric, T., Tavecchio, F., Temnikov, P., Terzic, T., Teshima, M., Torres-Alba, N., Tsujimoto, S., Van Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Vovk, I., Will, M., Zaric, D., Aller, H. D., Aller, M. F., Carini, M. T., Horan, D., Jordan, B., Jorstad, S. G., Kurtanidze, O. M., Kurtanidze, S. O., Lahteenmaki, A., Larionov, V. M., Larionova, E. G., Madejski, G., Marscher, A. P., Max-Moerbeck, W., Moody, J. W., Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Sigua, L. A., Smith, P. S., Talvikki, H., Tammi, J., Tornikoski, M., Troitsky, I. S., and Villata, M.
Subjects: Multiple days, Gamma-ray astronomY, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Flux, Markarian galaxies, Astrophysics, Blazar, 01 natural sciences, 7. Clean energy, BL Lacertae object, High energy astrophysic, law.invention, law, Observatory, BL Lacertae objects, Blazars, High energy astrophysics, Relativistic jets, Gamma-ray astronomy, Time domain astronomy, Relativistic jet, 0103 physical sciences, MAGIC (telescope), BL lacertae objects, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Astronomy and Astrophysics, Light curve, Space and Planetary Science, Markarian galaxie, Electrónica, Electricidad, Flare
Abstract: We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ∼27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsahovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ∼25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ⪆ 33) and the size of the emission region (δR≲ 3.8 × 10cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model., This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Smithsonian Institution, and NSERC in Canada. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy’s Office of Science, and the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under contract No. DE-AC02- 05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and the collaborating institutions in the construction and operation of the instrument. The MAGIC collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2- R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015- 71662-C2-2-P, FPA201790566REDC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, and the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV2015-0548 and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782, the University of Rijeka Project 13.12.1.3.02, the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382, and the Brazilian MCTIC, CNPq, and FAPERJ. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University, Finland, and the OVRO 40 m monitoring program, which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST1109911. The UMRAO data were obtained through NSF grant AST 0607523 and NASA Fermi GI award NNX09AU16G. The St. Petersburg University team acknowledges support from Russian RFBR foundation, grant 12-02-00452. The Abastumani Observatory team acknowledges financial support by the Shota Rustaveli National Science Foundation through project FR/577/6-320/13. The Steward Observatory data were obtained under Fermi Guest Investigator Program grant NNX09AU10G. The research at Boston University is supported by NASA grant 80NSSC17K0649 and NSF grant AST-1615796. Software. VEGAS (Cogan 2008), Event Display (Daniel 2008), MARS (Moralejo et al. 2009), Fermi Science Tools81, HEASoft (FTOOLS+XANADU; HEASARC 2014), REX,85 Xspec (Arnaud 1996), emcee (Foreman-Mackey et al. 2013).
Published: 2020

42. Multiwavelength variability and correlation studies of Mrk421 during historically low X-ray and $\upgamma$-ray activity in 2015{\textendash}2016

Author: Biswajit, Banerjee, Acciari, Victor A., Stefano, Ansoldi, Lucio Angelo Antonelli, Axel Arbet Engels, Manuel, Artero, Katsuaki, Asano, Dominik, Baack, Ana, Babi('(c)), Andr('(e))s, Baquero, Ulisses Barres de Almeida, Juan Abel Barrio, Ivana, Batkovi('(c)), Josefa Becerra Gonz('(a))lez, Wlodek, Bednarek, Lorenzo, Bellizzi, Elisa, Bernardini, Maria-Isabel, Bernardos, Alessio, Berti, Jürgen, Besenrieder, Wrijupan, Bhattacharyya, Ciro, Bigongiari, Adrian, Biland, Oscar, Blanch, Hendrik, Bökenkamp, Giacomo Bonnoli, ( (Z))eljka Bo( (s))njak, Giovanni, Busetto, Roberto, Carosi, Giovanni, Ceribella, Matteo, Cerruti, Yating, Chai, Ashot, Chilingarian, Stefan, Cikota, Sidika Merve Colak, Eduardo, Colombo, Jose Luis Contreras, Juan, Cortina, Stefano, Covino, Giacomo D( extquotesingle)Amico, Valerio D( extquotesingle)Elia, Paolo Da Vela, Francesco, Dazzi, Alessandro De Angelis, Barbara De Lotto, Manuel, Delfino, Jordi, Delgado, Carlos Delgado Mendez, Davide, Depaoli, Federico Di Pierro, Leonardo Di Venere, Elia Do Souto Espi(~(n))eira, Dijana Dominis Prester, Alice, Donini, Daniela, Dorner, Michele, Doro, Dominik, Elsaesser, Vandad Fallah Ramazani, Alicia, Fattorini, Maria Victoria Fonseca, Lluis, Font, Christian, Fruck, Satoshi, Fukami, Yasushi, Fukazawa, Garc('(i))a L('(o))pez, Ramon J., Markus, Garczarczyk, Sargis, Gasparyan, Markus, Gaug, Giglietto, Nicola, Francesco, Giordano, Pawel, Gliwny, Nikola, Godinovi('(c)), David, Green, Jarred Gershon Green, Daniela, Hadasch, Alexander, Hahn, Lea, Heckmann, Javier, Herrera, John, Hoang, Dario, Hrupec, Moritz, Hütten, Tomohiro, Inada, Kazuma, Ishio, Yuki, Iwamura, Irene Jim('(e))nez Mart('(i))nez, Jenni, Jormanainen, L('(e))a, Jouvin, Marie, Karjalainen, Daniel, Kerszberg, Yukiho, Kobayashi, Hidetoshi, Kubo, Junko, Kushida, Alessandra, Lamastra, Damir, Lelas, Francesco, Leone, Elina, Lindfors, Lena, Linhoff, Saverio, Lombardi, Francesco, Longo, Rub('(e))n, L('(o))pez-Coto, Marcos, L('(o))pez-Moya, Alicia, L('(o))pez-Oramas, Loporchio, Serena, Bernardo Machado de Oliveira Fraga, Camilla, Maggio, Pratik, Majumdar, Martin, Makariev, Manuela, Mallamaci, Galina, Maneva, Marina, Manganaro, Karl, Mannheim, Laura, Maraschi, Mos(`(e)), Mariotti, Manel, Mart('(i))nez, Daniel, Mazin, Stefano, Menchiari, Simone, Mender, Sa( (s))a Mi('(c))anovi('(c)), Davide, Miceli, Tjark, Miener, Jose Miguel Miranda, Razmik, Mirzoyan, Edgar, Molina, Abelardo, Moralejo, Daniel, Morcuende, Victoria, Moreno, Elena, Moretti, Takeshi, Nakamori, Lara, Nava, Vitaly, Neustroev, Cosimo, Nigro, Kari, Nilsson, Kyoshi, Nishijima, Koji, Noda, Seiya, Nozaki, Yoshiki, Ohtani, Tomohiko, Oka, Jorge, Otero-Santos, Simona, Paiano, Michele, Palatiello, David, Paneque, Riccardo, Paoletti, Paredes, Josep M., Lovro, Pavleti('(c)), Pablo, Pe(~(n))il, Massimo, Persic, Marine, Pihet, Pier Giorgio Prada Moroni, Elisa, Prandini, Chaitanya, Priyadarshi, Ivica, Puljak, Wolfgang, Rhode, Marc, Rib('(o)), Javier, Rico, Chiara, Righi, Andrea, Rugliancich, Narek, Sahakyan, Takayuki, Saito, Shunsuke, Sakurai, Konstancja, Satalecka, Francesco Gabriele Saturni, Bernd, Schleicher, Kevin, Schmidt, Thomas, Schweizer, Julian, Sitarek, Iva, ( (S))nidari('(c)), Dorota, Sobczy('(n))ska, Alessia, Spolon, Antonio, Stamerra, Jelena Stri( (s))kovi('(c)), Derek, Strom, Marcel, Strzys, Yusuke, Suda, Tihomir, Suri('(c)), Mitsunari, Takahashi, Ryuji, Takeishi, Fabrizio, Tavecchio, Petar, Temnikov, Tomislav, Terzi('(c)), Masahiro, Teshima, Luca, Tosti, Stefano, Truzzi, Antonio, Tutone, Santiago, Ubach, Juliane van Scherpenberg, Gaia, Vanzo, Monica VAZQUEZ ACOSTA, Sofia, Ventura, Vassil, Verguilov, Carlo Francesco Vigorito, Vincenzo, Vitale, Ievgen, Vovk, Martin, Will, Carolin, Wunderlich, Tokonatsu, Yamamoto, Darko, Zari('(c)), Matteo, Balbo, Thomas, Bretz, Jens, Buss, Laura, Eisenberger, Dorothee, Hildebrand, Roman, Iotov, Adelina, Kalenski, Alison, Mitchell, Dominik, Neise, Maximilian, Noethe, Aleksander, Paravac, Vitalii, Sliusar, Roland, Walter, Valverde, J., Horan, D., Giroletti, M., Perri, M., Verrecchia, F., Leto, C., Sadun, A. C., Moody, J. W., Joner, M., Marscher, A. P., Jorstad, S. G., Lähteenmäki, A., ( extasciitilde)Tornikoski, M., Ramakrishnan, V., Järvelä, E., Vera, R. J. C., Righini, S., Lien, A. Y., and And
Published: 2021

43. Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and γ-ray activity in 2015-2016

Author: Banerjee, B., Terzić, T., Paneque, D., Majumdar, P., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Artero, M., Asano, K., Babić, A., Banrje, B., Baquero, A., Barres Almeida, U., Barrio, J. A., Batković, I., Becerra González, J., Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Blanch, O., Bökenkamp, H., Bonnoli, G., Bošnjak, Ž, Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Giacomo D'Amico, D’elia, V., Da Vela, P., Dazzi, F., Angelis, A., Lotto, B., Delfino, M., Delgado, J., Delgado Mendez, C., Depaoli, D., Di Pierro, F., Di Venere, L., Do Souto Espiñeira, E., Dominis Prester, D., Donini, A., Doro, M., Fallah Ramazani, V., Fattorini, A., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Fukazawa, Y., García López, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Inada, T., Ishio, K., Iwamura, Y., Jiménez Martínez, I., Jormanainen, J., Jouvin, L., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Linhoff, L., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Machado Oliveira Fraga, B., Maggio, C., Righini, S., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Nakamori, T., Nava, L., Neustroev, V., Nigro, C., Nilsson, K., Nishijima, K., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Paiano, S., Palatiello, M., Vera, R. J. C., Paoletti, R., Paredes, J. M., Pavletić, L., Peñil, P., Persic, M., Pihet, M., Prada Moroni, P. G., Prandini, E., Priyadarshi, C., Puljak, I., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Lien, A. Y., Schmidt, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Surić, T., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Järvelä, E., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Wunderlich, C., Yamamoto, T., Zarić, D., Arbet-Engels, A., Baack, D., Balbo, M., Biland, A., Bretz, T., Buss, J., Dorner, D., Eisenberger, L., Elsaesser, D., Hildebrand, D., Iotov, R., Kalenski, A., Mannheim, K., Mitchell, A., Neise, D., Noethe, M., Paravac, A., Rhode, W., Schleicher, B., Sliusar, V., Walter, R., Valverde, J., Horan, D., Giroletti, M., Perri, M., Verrecchia, F., Leto, C., Sadun, A. C., Moody, J. W., Joner, M., Marscher, A. P., Jorstad, S. G., Lähteenmäki, A., Tornikoski, M., Ramakrishnan, V., Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), MAGIC, ITA, USA, GBR, DEU, ARM, BRA, CHL, HRV, FIN, JPN, IND, POL, RUS, CHE, German Research Foundation, Istituto Nazionale di Fisica Nucleare, Istituto Nazionale di Astrofisica, Swiss National Science Foundation, Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía y Competitividad (España), Department of Atomic Energy (India), Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology (Japan), Ministry of Education, Youth and Science (Bulgaria), Academy of Finland, University of Tokyo, La Caixa, University of Rijeka, Polish National Agency for Academic Exchange, Ministério da Ciência e Tecnologia (Brasil), Croatian Science Foundation, Department of Electronics and Nanoengineering, Metsähovi Radio Observatory, Aalto-yliopisto, Aalto University, Acciari, Va, Ansoldi, S, Antonelli, La, Asano, K, Babic, A, Banerjee, B, Baquero, A, de Almeida, Ub, Barrio, Ja, Gonzalez, Jb, Bednarek, W, Bellizzi, L, Bernardini, E, Bernardos, M, Berti, A, Besenrieder, J, Bhattacharyya, W, Bigongiari, C, Blanch, O, Bonnoli, G, Bosnjak, Z, Busetto, G, Carosi, R, Ceribella, G, Cerruti, M, Chai, Y, Chilingarian, A, Cikota, S, Colak, Sm, Colombo, E, Contreras, Jl, Cortina, J, Covino, S, D'Amico, G, D'Elia, V, Da Vela, P, Dazzi, F, De Angelis, A, De Lotto, B, Delfino, M, Delgado, J, Mendez, Cd, Depaoli, D, Di Girolamo, T, Di Pierro, F, Di Venere, L, Neira, Ede, Prester, Dd, Donini, A, Doro, M, Ramazani, Vf, Fattorini, A, Ferrara, G, Foffano, L, Fonseca, Mv, Font, L, Fruck, C, Fukami, S, Lopez, Rjg, Garczarczyk, M, Gasparyan, S, Gaug, M, Giglietto, N, Giordano, F, Gliwny, P, Green, Jg, Green, D, Hadasch, D, Hahn, A, Heckmann, L, Herrera, J, Hoang, J, Hrupec, D, Hutten, M, Inada, T, Inoue, S, Ishio, K, Iwamura, Y, Jormanainen, J, Jouvin, L, Kajiwara, Y, Karjalainen, M, Kerszberg, D, Kobayashi, Y, Kubo, H, Kushida, J, Lamastra, A, Lelas, D, Leone, F, Lindfors, E, Lombardi, S, Longo, F, Lopez, M, Lopez-Coto, R, Lopez-Oramas, A, Loporchio, S, Fraga, Bmd, Maggio, C, Majumdar, P, Makariev, M, Mallamaci, M, Maneva, G, Manganaro, M, Maraschi, L, Mariotti, M, Martinez, M, Mazin, D, Mender, S, Micanovic, S, Miceli, D, Miener, T, Minev, M, Miranda, Jm, Mirzoyan, R, Molina, E, Moralejo, A, Morcuende, D, Moreno, V, Moretti, E, Munar-Adrover, P, Neustroev, V, Nigro, C, Nilsson, K, Ninci, D, Nishijima, K, Noda, K, Nozaki, S, Ohtani, Y, Oka, T, Otero-Santos, J, Palatiello, M, Paneque, D, Paoletti, R, Paredes, Jm, Pavletic, L, Penil, P, Perennes, C, Persic, M, Moroni, Pgp, Prandini, E, Priyadarshi, C, Puljak, I, Rhode, W, Ribo, M, Rico, J, Righi, C, Rugliancich, A, Saha, L, Sahakyan, N, Saito, T, Sakurai, S, Satalecka, K, Schleicher, B, Schmidt, K, Schweizer, T, Sitarek, J, Snidaric, I, Sobczynska, D, Spolon, A, Stamerra, A, Strom, D, Strzys, M, Suda, Y, Suric, T, Takahashi, M, Tavecchio, F, Temnikov, P, Terzic, T, Teshima, M, Torres-Alba, N, Tosti, L, Truzzi, S, van Scherpenberg, J, Vanzo, G, Acosta, Mv, Ventura, S, Verguilov, V, Vigorito, Cf, Vitale, V, Vovk, I, Will, M, Zaric, D, Arbet-Engels, A, Baack, D, Balbo, M, Beck, M, Biederbeck, N, Biland, A, Bretz, T, Bruegge, K, Buss, J, Dorner, D, Elsaesser, D, Hildebrand, D, Iotov, R, Klinger, M, Mannheim, K, Neise, D, Neronov, A, Noethe, M, Paravac, A, Sliusar, V, Theissen, F, Walter, R, Valverde, J, Horan, D, Giroletti, M, Perri, M, Verrecchia, F, Leto, C, Sadun, Ac, Moody, Jw, Joner, M, Marscher, Ap, Jorstad, Sg, Lahteenmaki, A, Tornikoski, M, Ramakrishnan, V, Jarvela, E, Vera, Rjc, Righini, S, and Lien, Ay
Subjects: BL Lacertae objects: individual: Mrk 421, galaxies: active, methods: data analysis, methods: observational, radiation mechanisms: non-thermal, Non-thermal, Astrophysics, 4/3, GeV, 01 natural sciences, law.invention, Correlation, law, optical, MAGIC (telescope), data analysis [Methods], 010303 astronomy & astrophysics, Physics, individual: Mrk 421 [BL Lacertae objects], radio wave, Gamma ray, Low activity, X-ray, non-thermal [radiation mechanisms], Synchrotron, Log-normal distribution, Electrónica, Electricidad, Astrophysics - High Energy Astrophysical Phenomena, Radio wave, active [Galaxies], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, VHE, GLAST, blazar, Flux (metallurgy), 0103 physical sciences, synchrotron, Radiation mechanisms, TeV, observational [Methods], Blazar, 010308 nuclear & particles physics, Astronomy and Astrophysics, Spectral component, MAGIC, flux, Space and Planetary Science, 13. Climate action, gamma ray, correlation, data analysi [methods], ddc:520, spectral, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Energy (signal processing)
Abstract: Acciari, V. A., et al. (MAGIC Collaboration), We report a characterization of the multiband flux variability and correlations of the nearby (z = 0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT, MAGIC, FACT, and other collaborations and instruments from 2014 November till 2016 June. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F>1 TeV < 1.7 × 10-12 ph cm-2 s-1) and in the 2-10 keV (X-ray) band (F 2-10, keV< 3.6× 10-11 erg cm-2 s-1), during which the Swift-BAT data suggest an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very high-energy (E > 0.1 TeV) γ-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HRkeV and HRTeV show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 d centred at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 d centred at a time lag of 43+9-6 d. This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a lognormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process., The financial support of the German BMBF and MPG; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish MINECO (FPA2017-87859-P, FPA2017-85668-P, FPA2017-82729-C6-2-R, FPA2017-82729-C6-6-R, FPA2017-82729-C6-5-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2017-87055-C2-2-P, FPA2017-90566-REDC); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-268/16.12.2019 and the Academy of Finland grant nr. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia ‘Severo Ochoa’ SEV-2016-0588 and SEV-2015-0548, the Unidad de Excelencia ‘María de Maeztu’ MDM-2014-0369 and the ‘la Caixa’ Foundation (fellowship LCF/BQ/PI18/11630012), by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq, and FAPERJ.
Published: 2021
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44. Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and gamma-ray activity in 2015–2016

Author: Acciari, V. A. (V. A.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Asano, K. (K.), Babic, A. (A.), Banerjee, B. (B.), Baquero, A. (A.), de Almeida, U. B. (U. Barres), Barrio, J. A. (J. A.), Becerra Gonzalez, J. (J.), Bednarek, W. (W.), Bellizzi, L. (L.), Bernardini, E. (E.), Bernardos, M. (M.), Berti, A. (A.), Besenrieder, J. (J.), Bhattacharyya, W. (W.), Bigongiari, C. (C.), Blanch, O. (O.), Bonnoli, G. (G.), Bosnjak, Z. (Z.), Busetto, G. (G.), Carosi, R. (R.), Ceribella, G. (G.), Cerruti, M. (M.), Chai, Y. (Y.), Chilingarian, A. (A.), Cikota, S. (S.), Colak, S. M. (S. M.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), D'Amico, G. (G.), D'Elia, V. (V), Da Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Delfino, M. (M.), Delgado, J. (J.), Delgado Mendez, C. (C.), Depaoli, D. (D.), Di Girolamo, T. (T.), Di Pierro, F. (F.), Di Venere, L. (L.), Espi Neira, E. D. (E. Do Souto), Prester, D. D. (D. Dominis), Donini, A. (A.), Doro, M. (M.), Ramazani, V. F. (V. Fallah), Fattorini, A. (A.), Ferrara, G. (G.), Foffano, L. (L.), Fonseca, M. V. (M., V), Font, L. (L.), Fruck, C. (C.), Fukami, S. (S.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gasparyan, S. (S.), Gaug, M. (M.), Giglietto, N. (N.), Giordano, F. (F.), Gliwny, P. (P.), Green, J. G. (J. G.), Green, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Heckmann, L. (L.), Herrera, J. (J.), Hoang, J. (J.), Hrupec, D. (D.), Huetten, M. (M.), Inada, T. (T.), Inoue, S. (S.), Ishio, K. (K.), Iwamura, Y. (Y.), Jormanainen, J. (J.), Jouvin, L. (L.), Kajiwara, Y. (Y.), Karjalainen, M. (M.), Kerszberg, D. (D.), Kobayashi, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Lamastra, A. (A.), Lelas, D. (D.), Leone, F. (F.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Lopez-Coto, R. (R.), Lopez-Oramas, A. (A.), Loporchio, S. (S.), de Oliveira Fraga, B. M. (B. Machado), Maggio, C. (C.), Majumdar, P. (P.), Makariev, M. (M.), Mallamaci, M. (M.), Maneva, G. (G.), Manganaro, M. (M.), Maraschi, L. (L.), Mariotti, M. (M.), Martinez, M. (M.), Mazin, D. (D.), Mender, S. (S.), Micanovic, S. (S.), Miceli, D. (D.), Miener, T. (T.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Molina, E. (E.), Moralejo, A. (A.), Morcuende, D. (D.), Moreno, V. (V), Moretti, E. (E.), Munar-Adrover, P. (P.), Neustroev, V. (V), Nigro, C. (C.), Nilsson, K. (K.), Ninci, D. (D.), Nishijima, K. (K.), Noda, K. (K.), Nozaki, S. (S.), Ohtani, Y. (Y.), Oka, T. (T.), Otero-Santos, J. (J.), Palatiello, M. (M.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Pavletic, L. (L.), Penil, P. (P.), Perennes, C. (C.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Priyadarshi, C. (C.), Puljak, I. (I), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saha, L. (L.), Sahakyan, N. (N.), Saito, T. (T.), Sakurai, S. (S.), Satalecka, K. (K.), Schleicher, B. (B.), Schmidt, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I), Sobczynska, D. (D.), Spolon, A. (A.), Stamerra, A. (A.), Strom, D. (D.), Strzys, M. (M.), Suda, Y. (Y.), Suric, T. (T.), Takahashi, M. (M.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Tosti, L. (L.), Truzzi, S. (S.), van Scherpenberg, J. (J.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Ventura, S. (S.), Verguilov, V. (V.), Vigorito, C. F. (C. F.), Vitale, V. (V.), Vovk, I. (I), Will, M. (M.), Zaric, D. (D.), Arbet-Engels, A. (A.), Baack, D. (D.), Balbo, M. (M.), Beck, M. (M.), Biederbeck, N. (N.), Biland, A. (A.), Bretz, T. (T.), Bruegge, K. (K.), Buss, J. (J.), Dorner, D. (D.), Elsaesser, D. (D.), Hildebrand, D. (D.), Iotov, R. (R.), Klinger, M. (M.), Mannheim, K. (K.), Neise, D. (D.), Neronov, A. (A.), Noethe, M. (M.), Paravac, A. (A.), Sliusar, V. (V), Theissen, F. (F.), Walter, R. (R.), Valverde, J. (J.), Horan, D. (D.), Giroletti, M. (M.), Perri, M. (M.), Verrecchia, F. (F.), Leto, C. (C.), Sadun, A. C. (A. C.), Moody, J. W. (J. W.), Joner, M. (M.), Marscher, A. P. (A. P.), Jorstad, S. G. (S. G.), Lahteenmaki, A. (A.), Tornikoski, M. (M.), Ramakrishnan, V. (V), Jarvela, E. (E.), Vera, R. J. (R. J. C.), Righini, S. (S.), Lien, A. Y. (A. Y.), Acciari, V. A. (V. A.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Asano, K. (K.), Babic, A. (A.), Banerjee, B. (B.), Baquero, A. (A.), de Almeida, U. B. (U. Barres), Barrio, J. A. (J. A.), Becerra Gonzalez, J. (J.), Bednarek, W. (W.), Bellizzi, L. (L.), Bernardini, E. (E.), Bernardos, M. (M.), Berti, A. (A.), Besenrieder, J. (J.), Bhattacharyya, W. (W.), Bigongiari, C. (C.), Blanch, O. (O.), Bonnoli, G. (G.), Bosnjak, Z. (Z.), Busetto, G. (G.), Carosi, R. (R.), Ceribella, G. (G.), Cerruti, M. (M.), Chai, Y. (Y.), Chilingarian, A. (A.), Cikota, S. (S.), Colak, S. M. (S. M.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), D'Amico, G. (G.), D'Elia, V. (V), Da Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Delfino, M. (M.), Delgado, J. (J.), Delgado Mendez, C. (C.), Depaoli, D. (D.), Di Girolamo, T. (T.), Di Pierro, F. (F.), Di Venere, L. (L.), Espi Neira, E. D. (E. Do Souto), Prester, D. D. (D. Dominis), Donini, A. (A.), Doro, M. (M.), Ramazani, V. F. (V. Fallah), Fattorini, A. (A.), Ferrara, G. (G.), Foffano, L. (L.), Fonseca, M. V. (M., V), Font, L. (L.), Fruck, C. (C.), Fukami, S. (S.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gasparyan, S. (S.), Gaug, M. (M.), Giglietto, N. (N.), Giordano, F. (F.), Gliwny, P. (P.), Green, J. G. (J. G.), Green, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Heckmann, L. (L.), Herrera, J. (J.), Hoang, J. (J.), Hrupec, D. (D.), Huetten, M. (M.), Inada, T. (T.), Inoue, S. (S.), Ishio, K. (K.), Iwamura, Y. (Y.), Jormanainen, J. (J.), Jouvin, L. (L.), Kajiwara, Y. (Y.), Karjalainen, M. (M.), Kerszberg, D. (D.), Kobayashi, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Lamastra, A. (A.), Lelas, D. (D.), Leone, F. (F.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Lopez-Coto, R. (R.), Lopez-Oramas, A. (A.), Loporchio, S. (S.), de Oliveira Fraga, B. M. (B. Machado), Maggio, C. (C.), Majumdar, P. (P.), Makariev, M. (M.), Mallamaci, M. (M.), Maneva, G. (G.), Manganaro, M. (M.), Maraschi, L. (L.), Mariotti, M. (M.), Martinez, M. (M.), Mazin, D. (D.), Mender, S. (S.), Micanovic, S. (S.), Miceli, D. (D.), Miener, T. (T.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Molina, E. (E.), Moralejo, A. (A.), Morcuende, D. (D.), Moreno, V. (V), Moretti, E. (E.), Munar-Adrover, P. (P.), Neustroev, V. (V), Nigro, C. (C.), Nilsson, K. (K.), Ninci, D. (D.), Nishijima, K. (K.), Noda, K. (K.), Nozaki, S. (S.), Ohtani, Y. (Y.), Oka, T. (T.), Otero-Santos, J. (J.), Palatiello, M. (M.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Pavletic, L. (L.), Penil, P. (P.), Perennes, C. (C.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Priyadarshi, C. (C.), Puljak, I. (I), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saha, L. (L.), Sahakyan, N. (N.), Saito, T. (T.), Sakurai, S. (S.), Satalecka, K. (K.), Schleicher, B. (B.), Schmidt, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I), Sobczynska, D. (D.), Spolon, A. (A.), Stamerra, A. (A.), Strom, D. (D.), Strzys, M. (M.), Suda, Y. (Y.), Suric, T. (T.), Takahashi, M. (M.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Tosti, L. (L.), Truzzi, S. (S.), van Scherpenberg, J. (J.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Ventura, S. (S.), Verguilov, V. (V.), Vigorito, C. F. (C. F.), Vitale, V. (V.), Vovk, I. (I), Will, M. (M.), Zaric, D. (D.), Arbet-Engels, A. (A.), Baack, D. (D.), Balbo, M. (M.), Beck, M. (M.), Biederbeck, N. (N.), Biland, A. (A.), Bretz, T. (T.), Bruegge, K. (K.), Buss, J. (J.), Dorner, D. (D.), Elsaesser, D. (D.), Hildebrand, D. (D.), Iotov, R. (R.), Klinger, M. (M.), Mannheim, K. (K.), Neise, D. (D.), Neronov, A. (A.), Noethe, M. (M.), Paravac, A. (A.), Sliusar, V. (V), Theissen, F. (F.), Walter, R. (R.), Valverde, J. (J.), Horan, D. (D.), Giroletti, M. (M.), Perri, M. (M.), Verrecchia, F. (F.), Leto, C. (C.), Sadun, A. C. (A. C.), Moody, J. W. (J. W.), Joner, M. (M.), Marscher, A. P. (A. P.), Jorstad, S. G. (S. G.), Lahteenmaki, A. (A.), Tornikoski, M. (M.), Ramakrishnan, V. (V), Jarvela, E. (E.), Vera, R. J. (R. J. C.), Righini, S. (S.), and Lien, A. Y. (A. Y.)
Abstract: We report a characterization of the multiband flux variability and correlations of the nearby (z = 0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT, MAGIC, FACT, and other collaborations and instruments from 2014 November till 2016 June. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F> 1 TeV < 1.7 × 10⁻¹² ph cm⁻² s⁻¹) and in the 2–10 keV (X-ray) band (F2–10 keV < 3.6 × 10⁻¹¹ erg cm⁻² s⁻¹), during which the Swift-BAT data suggest an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very high-energy (E > 0.1 TeV) gamma-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HRkeV and HRTeV show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 d centred at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 d centred at a time lag of $43_{-6}^{+9}$ d. This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a lognormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process.
Published: 2021

45. Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and γ-ray activity in 2015–2016

Author: Acciari, V A, primary, Ansoldi, S, additional, Antonelli, L A, additional, Asano, K, additional, Babić, A, additional, Banerjee, B, additional, Baquero, A, additional, de Almeida, U Barres, additional, Barrio, J A, additional, González, J Becerra, additional, Bednarek, W, additional, Bellizzi, L, additional, Bernardini, E, additional, Bernardos, M, additional, Berti, A, additional, Besenrieder, J, additional, Bhattacharyya, W, additional, Bigongiari, C, additional, Blanch, O, additional, Bonnoli, G, additional, Bošnjak, Ž, additional, Busetto, G, additional, Carosi, R, additional, Ceribella, G, additional, Cerruti, M, additional, Chai, Y, additional, Chilingarian, A, additional, Cikota, S, additional, Colak, S M, additional, Colombo, E, additional, Contreras, J L, additional, Cortina, J, additional, Covino, S, additional, D’Amico, G, additional, D’Elia, V, additional, Da Vela, P, additional, Dazzi, F, additional, De Angelis, A, additional, De Lotto, B, additional, Delfino, M, additional, Delgado, J, additional, Mendez, C Delgado, additional, Depaoli, D, additional, Girolamo, T Di, additional, Pierro, F Di, additional, Venere, L Di, additional, Espi neira, E Do Souto, additional, Prester, D Dominis, additional, Donini, A, additional, Doro, M, additional, Ramazani, V Fallah, additional, Fattorini, A, additional, Ferrara, G, additional, Foffano, L, additional, Fonseca, M V, additional, Font, L, additional, Fruck, C, additional, Fukami, S, additional, López, R J García, additional, Garczarczyk, M, additional, Gasparyan, S, additional, Gaug, M, additional, Giglietto, N, additional, Giordano, F, additional, Gliwny, P, additional, Godinović, N, additional, Green, J G, additional, Green, D, additional, Hadasch, D, additional, Hahn, A, additional, Heckmann, L, additional, Herrera, J, additional, Hoang, J, additional, Hrupec, D, additional, Hütten, M, additional, Inada, T, additional, Inoue, S, additional, Ishio, K, additional, Iwamura, Y, additional, Jormanainen, J, additional, Jouvin, L, additional, Kajiwara, Y, additional, Karjalainen, M, additional, Kerszberg, D, additional, Kobayashi, Y, additional, Kubo, H, additional, Kushida, J, additional, Lamastra, A, additional, Lelas, D, additional, Leone, F, additional, Lindfors, E, additional, Lombardi, S, additional, Longo, F, additional, López, M, additional, López-Coto, R, additional, López-Oramas, A, additional, Loporchio, S, additional, Fraga, B Machado de Oliveira, additional, Maggio, C, additional, Majumdar, P, additional, Makariev, M, additional, Mallamaci, M, additional, Maneva, G, additional, Manganaro, M, additional, Maraschi, L, additional, Mariotti, M, additional, Martínez, M, additional, Mazin, D, additional, Mender, S, additional, Mićanović, S, additional, Miceli, D, additional, Miener, T, additional, Minev, M, additional, Miranda, J M, additional, Mirzoyan, R, additional, Molina, E, additional, Moralejo, A, additional, Morcuende, D, additional, Moreno, V, additional, Moretti, E, additional, Munar-Adrover, P, additional, Neustroev, V, additional, Nigro, C, additional, Nilsson, K, additional, Ninci, D, additional, Nishijima, K, additional, Noda, K, additional, Nozaki, S, additional, Ohtani, Y, additional, Oka, T, additional, Otero-Santos, J, additional, Palatiello, M, additional, Paneque, D, additional, Paoletti, R, additional, Paredes, J M, additional, Pavletić, L, additional, Pe nil, P, additional, Perennes, C, additional, Persic, M, additional, Moroni, P G Prada, additional, Prandini, E, additional, Priyadarshi, C, additional, Puljak, I, additional, Rhode, W, additional, Ribó, M, additional, Rico, J, additional, Righi, C, additional, Rugliancich, A, additional, Saha, L, additional, Sahakyan, N, additional, Saito, T, additional, Sakurai, S, additional, Satalecka, K, additional, Schleicher, B, additional, Schmidt, K, additional, Schweizer, T, additional, Sitarek, J, additional, Šnidarić, I, additional, Sobczynska, D, additional, Spolon, A, additional, Stamerra, A, additional, Strom, D, additional, Strzys, M, additional, Suda, Y, additional, Surić, T, additional, Takahashi, M, additional, Tavecchio, F, additional, Temnikov, P, additional, Terzić, T, additional, Teshima, M, additional, Torres-Albà, N, additional, Tosti, L, additional, Truzzi, S, additional, van Scherpenberg, J, additional, Vanzo, G, additional, Acosta, M Vazquez, additional, Ventura, S, additional, Verguilov, V, additional, Vigorito, C F, additional, Vitale, V, additional, Vovk, I, additional, Will, M, additional, Zarić, D, additional, Arbet-Engels, A, additional, Baack, D, additional, Balbo, M, additional, Beck, M, additional, Biederbeck, N, additional, Biland, A, additional, Bretz, T, additional, Bruegge, K, additional, Buss, J, additional, Dorner, D, additional, Elsaesser, D, additional, Hildebrand, D, additional, Iotov, R, additional, Klinger, M, additional, Mannheim, K, additional, Neise, D, additional, Neronov, A, additional, Noethe, M, additional, Paravac, A, additional, Sliusar, V, additional, Theissen, F, additional, Walter, R, additional, Valverde, J, additional, Horan, D, additional, Giroletti, M, additional, Perri, M, additional, Verrecchia, F, additional, Leto, C, additional, Sadun, A C, additional, Moody, J W, additional, Joner, M, additional, Marscher, A P, additional, Jorstad, S G, additional, Lähteenmäki, A, additional, Tornikoski, M, additional, Ramakrishnan, V, additional, Järvelä, E, additional, Vera, R J C, additional, Righini, S, additional, and Lien, A Y, additional
Published: 2020
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46. Unraveling the Complex Behavior of Mrk 421 with Simultaneous X-Ray and VHE Observations during an Extreme Flaring Activity in 2013 April *

Author: Acciari, V. A., primary, Ansoldi, S., additional, Antonelli, L. A., additional, Engels, A. Arbet, additional, Baack, D., additional, Babić, A., additional, Banerjee, B., additional, de Almeida, U. Barres, additional, Barrio, J. A., additional, González, J. Becerra, additional, Bednarek, W., additional, Bellizzi, L. K., additional, Bernardini, E., additional, Berti, A., additional, Besenrieder, J., additional, Bhattacharyya, W., additional, Bigongiari, C., additional, Biland, A., additional, Blanch, O., additional, Bonnoli, G., additional, Bošnjak, Ž., additional, Busetto, G., additional, Carosi, R., additional, Ceribella, G., additional, Cerruti, M., additional, Chai, Y., additional, Chilingarian, A., additional, Cikota, S., additional, Colak, S. M., additional, Colin, U., additional, Colombo, E., additional, Contreras, J. L., additional, Cortina, J., additional, Covino, S., additional, D’Elia, V., additional, Vela, P. Da, additional, Dazzi, F., additional, Angelis, A. De, additional, Lotto, B. De, additional, Puppo, F. Del, additional, Delfino, M., additional, Delgado, J., additional, Depaoli, D., additional, Pierro, F. Di, additional, Venere, L. Di, additional, Souto Espiñeira, E. Do, additional, Prester, D. Dominis, additional, Donini, A., additional, Dorner, D., additional, Doro, M., additional, Elsaesser, D., additional, Ramazani, V. Fallah, additional, Fattorini, A., additional, Ferrara, G., additional, Foffano, L., additional, Fonseca, M. V., additional, Font, L., additional, Fruck, C., additional, Fukami, S., additional, López, R. J. García, additional, Garczarczyk, M., additional, Gasparyan, S., additional, Gaug, M., additional, Giglietto, N., additional, Giordano, F., additional, Gliwny, P., additional, Godinović, N., additional, Green, D., additional, Hadasch, D., additional, Hahn, A., additional, Hassan, T., additional, Herrera, J., additional, Hoang, J., additional, Hrupec, D., additional, Hütten, M., additional, Inada, T., additional, Inoue, S., additional, Ishio, K., additional, Iwamura, Y., additional, Jouvin, L., additional, Kajiwara, Y., additional, Kerszberg, D., additional, Kobayashi, Y., additional, Kubo, H., additional, Kushida, J., additional, Lamastra, A., additional, Lelas, D., additional, Leone, F., additional, Lindfors, E., additional, Lombardi, S., additional, Longo, F., additional, López, M., additional, López-Coto, R., additional, López-Oramas, A., additional, Loporchio, S., additional, de Oliveira Fraga, B. Machado, additional, Maggio, C., additional, Majumdar, P., additional, Makariev, M., additional, Mallamaci, M., additional, Maneva, G., additional, Manganaro, M., additional, Mannheim, K., additional, Maraschi, L., additional, Mariotti, M., additional, Martínez, M., additional, Mazin, D., additional, Mender, S., additional, Mićanović, S., additional, Miceli, D., additional, Miener, T., additional, Minev, M., additional, Miranda, J. M., additional, Mirzoyan, R., additional, Molina, E., additional, Moralejo, A., additional, Morcuende, D., additional, Moreno, V., additional, Moretti, E., additional, Munar-Adrover, P., additional, Neustroev, V., additional, Nigro, C., additional, Nilsson, K., additional, Ninci, D., additional, Nishijima, K., additional, Noda, K., additional, Nogués, L., additional, Nozaki, S., additional, Ohtani, Y., additional, Oka, T., additional, Otero-Santos, J., additional, Palatiello, M., additional, Paneque, D., additional, Paoletti, R., additional, Paredes, J. M., additional, Pavletić, L., additional, Peñil, P., additional, Peresano, M., additional, Persic, M., additional, Moroni, P. G. Prada, additional, Prandini, E., additional, Puljak, I., additional, Rhode, W., additional, Ribó, M., additional, Rico, J., additional, Righi, C., additional, Rugliancich, A., additional, Saha, L., additional, Sahakyan, N., additional, Saito, T., additional, Sakurai, S., additional, Satalecka, K., additional, Schleicher, B., additional, Schmidt, K., additional, Schweizer, T., additional, Sitarek, J., additional, Šnidarić, I., additional, Sobczynska, D., additional, Spolon, A., additional, Stamerra, A., additional, Strom, D., additional, Strzys, M., additional, Suda, Y., additional, Surić, T., additional, Takahashi, M., additional, Tavecchio, F., additional, Temnikov, P., additional, Terzić, T., additional, Teshima, M., additional, Torres-Albà, N., additional, Tosti, L., additional, Scherpenberg, J. van, additional, Vanzo, G., additional, Acosta, M. Vazquez, additional, Ventura, S., additional, Verguilov, V., additional, Vigorito, C. F., additional, Vitale, V., additional, Vovk, I., additional, Will, M., additional, Zarić, D., additional, Collaboration), (MAGIC, additional, Petropoulou, M., additional, Finke, J., additional, D’Ammando, F., additional, Baloković, M., additional, Madejski, G., additional, Mori, K., additional, Puccetti, Simonetta, additional, Leto, C., additional, Perri, M., additional, Verrecchia, F., additional, Villata, M., additional, Raiteri, C. M., additional, Agudo, I., additional, Bachev, R., additional, Berdyugin, A., additional, Blinov, D. A., additional, Chanishvili, R., additional, Chen, W. P., additional, Chigladze, R., additional, Damljanovic, G., additional, Eswaraiah, C., additional, Grishina, T. S., additional, Ibryamov, S., additional, Jordan, B., additional, Jorstad, S. G., additional, Joshi, M., additional, Kopatskaya, E. N., additional, Kurtanidze, O. M., additional, Kurtanidze, S. O., additional, Larionova, E. G., additional, Larionova, L. V., additional, Larionov, V. M., additional, Latev, G., additional, Lin, H. C., additional, Marscher, A. P., additional, Mokrushina, A. A., additional, Morozova, D. A., additional, Nikolashvili, M. G., additional, Semkov, E., additional, Smith, P. S., additional, Strigachev, A., additional, Troitskaya, Yu. V., additional, Troitsky, I. S., additional, Vince, O., additional, Barnes, J., additional, Güver, T., additional, Moody, J. W., additional, Sadun, A. C., additional, Hovatta, T., additional, Richards, J. L., additional, Max-Moerbeck, W., additional, Readhead, A. C. S., additional, Lähteenmäki, A., additional, Tornikoski, M., additional, Tammi, J., additional, Ramakrishnan, V., additional, and Reinthal, R., additional
Published: 2020
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47. The Great Markarian 421 flare of 2010 February:multiwavelength variability and correlation studies

Author: Abeysekara, A. U. (A. U.), Benbow, W. (W.), Bird, R. (R.), Brill, A. (A.), Brose, R. (R.), Buchovecky, M. (M.), Buckley, J. H. (J. H.), Christiansen, J. L. (J. L.), Chromey, A. J. (A. J.), Daniel, M. K. (M. K.), Dumm, J. (J.), Falcone, A. (A.), Feng, Q. (Q.), Finley, J. P. (J. P.), Fortson, L. (L.), Furniss, A. (A.), Galante, N. (N.), Gent, A. (A.), Gillanders, G. H. (G. H.), Giuri, C. (C.), Gueta, O. (O.), Hassan, T. (T.), Hervet, O. (O.), Holder, J. (J.), Hughes, G. (G.), Humensky, T. B. (T. B.), Johnson, C. A. (C. A.), Kaaret, P. (P.), Kar, P. (P.), Kelley-Hoskins, N. (N.), Kertzman, M. (M.), Kieda, D. (D.), Krause, M. (M.), Krennrich, F. (F.), Kumar, S. (S.), Lang, M. J. (M. J.), Moriarty, P. (P.), Mukherjee, R. (R.), Nelson, T. (T.), Nieto, D. (D.), Nievas-Rosillo, M. (M.), O'Brien, S. (S.), Ong, R. A. (R. A.), Otte, A. N. (A. N.), Park, N. (N.), Petrashyk, A. (A.), Pichel, A. (A.), Pohl, M. (M.), Prado, R. R. (R. R.), Pueschel, E. (E.), Quinn, J. (J.), Ragan, K. (K.), Reynolds, P. T. (P. T.), Richards, G. T. (G. T.), Roache, E. (E.), Rovero, A. C. (A. C.), Rulten, C. (C.), Sadeh, I. (I), Santander, M. (M.), Sembroski, G. H. (G. H.), Shahinyan, K. (K.), Stevenson, B. (B.), Sushch, I. (I), Tyler, J. (J.), Vassiliev, V. V. (V. V.), Wakely, S. P. (S. P.), Weinstein, A. (A.), Wells, R. M. (R. M.), Wilcox, P. (P.), Wilhelm, A. (A.), Williams, D. A. (D. A.), Zitzer, B. (B.), Acciari, V. A. (V. A.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Engels, A. A. (A. Arbet), Baack, D. (D.), Babic, A. (A.), Banerjee, B. (B.), Barres de Almeida, U. (U.), Barrio, J. A. (J. A.), Becerra Gonzalez, J. (J.), Bednarek, W. (W.), Bellizzi, L. (L.), Bernardini, E. (E.), Berti, A. (A.), Besenrieder, J. (J.), Bhattacharyya, W. (W.), Bigongiari, C. (C.), Biland, A. (A.), Blanch, O. (O.), Bonnoli, G. (G.), Busetto, G. (G.), Carosi, R. (R.), Ceribella, G. (G.), Chai, Y. (Y.), Cikota, S. (S.), Colak, S. M. (S. M.), Colin, U. (U.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), D'Elia, V. (V), Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Delfino, M. (M.), Delgado, J. (J.), Di Pierro, F. (F.), Souto Espinera, E. (E.), Prester, D. D. (D. Dominis), Dorner, D. (D.), Doro, M. (M.), Einecke, S. (S.), Elsaesser, D. (D.), Ramazani, V. F. (V. Fallah), Fattorini, A. (A.), Fernandez-Barral, A. (A.), Ferrara, G. (G.), Fidalgo, D. (D.), Foffano, L. (L.), Fonseca, M. V. (M., V), Font, L. (L.), Fruck, C. (C.), Galindo, D. (D.), Gallozzi, S. (S.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gasparyan, S. (S.), Gaug, M. (M.), Godinovic, N. (N.), Green, D. (D.), Guberman, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Herrera, J. (J.), Hoang, J. (J.), Hrupec, D. (D.), Inoue, S. (S.), Ishio, K. (K.), Iwamura, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Lamastra, A. (A.), Lelas, D. (D.), Leone, F. (F.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Lopez-Coto, R. (R.), Lopez-Oramas, A. (A.), Machado de Oliveira Fraga, B. (B.), Maggio, C. (C.), Majumdar, P. (P.), Makariev, M. (M.), Mallamaci, M. (M.), Maneva, G. (G.), Manganaro, M. (M.), Mannheim, K. (K.), Maraschi, L. (L.), Mariotti, M. (M.), Martinez, M. (M.), Masuda, S. (S.), Mazin, D. (D.), Miceli, D. (D.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Molina, E. (E.), Moralejo, A. (A.), Morcuende, D. (D.), Moreno, V. (V), Moretti, E. (E.), Munar-Adrover, P. (P.), Neustroev, V. (V), Niedzwiecki, A. (A.), Nievas Rosillo, M. (M.), Nigro, C. (C.), Nilsson, K. (K.), Ninci, D. (D.), Nishijima, K. (K.), Noda, K. (K.), Nogues, L. (L.), Noethe, M. (M.), Paiano, S. (S.), Palacio, J. (J.), Palatiello, M. (M.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Penil, P. (P.), Peresano, M. (M.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Puljak, I. (I), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saha, L. (L.), Sahakyan, N. (N.), Saito, T. (T.), Satalecka, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I), Sobczynska, D. (D.), Somero, A. (A.), Stamerra, A. (A.), Strom, D. (D.), Strzys, M. (M.), Sun, S. (S.), Suric, T. (T.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Tsujimoto, S. (S.), van Scherpenberg, J. (J.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Vovk, I. (I), Will, M. (M.), Zaric, D. (D.), Aller, H. D. (H. D.), Aller, M. F. (M. F.), Carini, M. T. (M. T.), Horan, D. (D.), Jordan, B. (B.), Jorstad, S. G. (S. G.), Kurtanidze, O. M. (O. M.), Kurtanidze, S. O. (S. O.), Lahteenmaki, A. (A.), Larionov, V. M. (V. M.), Larionova, E. G. (E. G.), Madejski, G. (G.), Marscher, A. P. (A. P.), Max-Moerbeck, W. (W.), Moody, J. W. (J. Ward), Morozova, D. A. (D. A.), Nikolashvili, M. G. (M. G.), Raiteri, C. M. (C. M.), Readhead, A. C. (A. C. S.), Richards, J. L. (J. L.), Sadun, A. C. (A. C.), Sakamoto, T. (T.), Sigua, L. A. (L. A.), Smith, P. S. (P. S.), Talvikki, H. (H.), Tammi, J. (J.), Tornikoski, M. (M.), Troitsky, I. S. (I. S.), and Villata, M. (M.)
Subjects: Gamma-ray astronomy, Astrophysics::High Energy Astrophysical Phenomena, Time domain astronomy, BL Lacertae objects, Markarian galaxies, Relativistic jets, High energy astrophysics, Blazars
Abstract: We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ~27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsähovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare “decline“ epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ~25–55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ≳ 33) and the size of the emission region (δ⁻¹ RB ≲ × 10¹³ cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux–flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model.
Published: 2020

48. Unraveling the complex behavior of Mrk 421 with simultaneous X-Ray and VHE observations during an extreme flaring activity in 2013 April

Author: Acciari, V. A. (V. A.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Engels, A. A. (A. Arbet), Baack, D. (D.), Babic, A. (A.), Banerjee, B. (B.), Barres de Almeida, U. (U.), Barrio, J. A. (J. A.), Becerra Gonzalez, J. (J.), Bednarek, W. (W.), Bellizzi, L. K. (L. K.), Bernardini, E. (E.), Berti, A. (A.), Besenrieder, J. (J.), Bhattacharyya, W. (W.), Bigongiari, C. (C.), Biland, A. (A.), Blanch, O. (O.), Bonnoli, G. (G.), Bosnjak, Z. (Z.), Busetto, G. (G.), Carosi, R. (R.), Ceribella, G. (G.), Cerruti, M. (M.), Chai, Y. (Y.), Chilingarian, A. (A.), Cikota, S. (S.), Colak, S. M. (S. M.), Colin, U. (U.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), D'Elia, V. (V), Da Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Del Puppo, F. (F.), Delfino, M. (M.), Delgado, J. (J.), Depaoli, D. (D.), Di Pierro, F. (F.), Di Venere, L. (L.), Do Souto Espineira, E. (E.), Prester, D. D. (D. Dominis), Donini, A. (A.), Dorner, D. (D.), Doro, M. (M.), Elsaesser, D. (D.), Ramazani, V. F. (V. Fallah), Fattorini, A. (A.), Ferrara, G. (G.), Foffano, L. (L.), Fonseca, M. V. (M., V), Font, L. (L.), Fruck, C. (C.), Fukami, S. (S.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gasparyan, S. (S.), Gaug, M. (M.), Giglietto, N. (N.), Giordano, F. (F.), Gliwny, P. (P.), Godinovic, N. (N.), Green, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Hassan, T. (T.), Herrera, J. (J.), Hoang, J. (J.), Hrupec, D. (D.), Huetten, M. (M.), Inada, T. (T.), Inoue, S. (S.), Ishio, K. (K.), Iwamura, Y. (Y.), Jouvin, L. (L.), Kajiwara, Y. (Y.), Kerszberg, D. (D.), Kobayashi, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Lamastra, A. (A.), Lelas, D. (D.), Leone, F. (F.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Lopez-Coto, R. (R.), Lopez-Oramas, A. (A.), Loporchio, S. (S.), Machado de Oliveira Fraga, B. (B.), Maggio, C. (C.), Majumdar, P. (P.), Makariev, M. (M.), Mallamaci, M. (M.), Maneva, G. (G.), Manganaro, M. (M.), Mannheim, K. (K.), Maraschi, L. (L.), Mariotti, M. (M.), Martinez, M. (M.), Mazin, D. (D.), Mender, S. (S.), Micanovic, S. (S.), Miceli, D. (D.), Miener, T. (T.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Molina, E. (E.), Moralejo, A. (A.), Morcuende, D. (D.), Moreno, V. (V), Moretti, E. (E.), Munar-Adrover, P. (P.), Neustroev, V. (V), Nigro, C. (C.), Nilsson, K. (K.), Ninci, D. (D.), Nishijima, K. (K.), Noda, K. (K.), Nogues, L. (L.), Nozaki, S. (S.), Ohtani, Y. (Y.), Oka, T. (T.), Otero-Santos, J. (J.), Palatiello, M. (M.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Pavletic, L. (L.), Penil, P. (P.), Peresano, M. (M.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Puljak, I. (I), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saha, L. (L.), Sahakyan, N. (N.), Saito, T. (T.), Sakurai, S. (S.), Satalecka, K. (K.), Schleicher, B. (B.), Schmidt, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I), Sobczynska, D. (D.), Spolon, A. (A.), Stamerra, A. (A.), Strom, D. (D.), Strzys, M. (M.), Suda, Y. (Y.), Suric, T. (T.), Takahashi, M. (M.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Tosti, L. (L.), van Scherpenberg, J. (J.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Ventura, S. (S.), Verguilov, V. (V.), Vigorito, C. F. (C. F.), Vitale, V. (V.), Vovk, I. (I), Will, M. (M.), Zaric, D. (D.), Petropoulou, M. (M.), Finke, J. (J.), D'Ammando, F. (F.), Balokovi, M. (M.), Madejskic, G. (G.), Mori, K. (K.), Puccetti, S. (Simonetta), Leto, C. (C.), Perri, M. (M.), Verrecchia, F. (F.), Villata, M. (M.), Raiteri, C. M. (C. M.), Agudo, I. (I), Bachev, R. (R.), Berdyugin, A. (A.), Blinov, D. A. (D. A.), Chanishvili, R. (R.), Chen, W. P. (W. P.), Chigladze, R. (R.), Damljanovic, G. (G.), Eswaraiah, C. (C.), Grishina, T. S. (T. S.), Ibryamov, S. (S.), Jordan, B. (B.), Jorstad, S. G. (S. G.), Joshi, M. (M.), Kopatskaya, E. N. (E. N.), Kurtanidze, O. M. (O. M.), Kurtanidze, S. O. (S. O.), Larionova, E. G. (E. G.), Larionova, L. V. (L., V), Larionov, V. M. (V. M.), Latev, G. (G.), Lin, H. C. (H. C.), Marscher, A. P. (A. P.), Mokrushina, A. A. (A. A.), Morozova, D. A. (D. A.), Nikolashvili, M. G. (M. G.), Semkov, E. (E.), Smith, P. S. (P. S.), Strigachev, A. (A.), Troitskaya, Y. V. (Yu, V), Troitsky, I. S. (I. S.), Vince, O. (O.), Barnes, J. (J.), Guver, T. (T.), Moody, J. W. (J. W.), Sadun, A. C. (A. C.), Hovatta, T. (T.), Richards, J. L. (J. L.), Max-Moerbeck, W. (W.), Readhead, A. C. (A. C. S.), Lahteenmaki, A. (A.), Tornikoski, M. (M.), Tammi, J. (J.), Ramakrishnan, V. (V), Reinthal, R. (R.), Acciari, V. A. (V. A.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Engels, A. A. (A. Arbet), Baack, D. (D.), Babic, A. (A.), Banerjee, B. (B.), Barres de Almeida, U. (U.), Barrio, J. A. (J. A.), Becerra Gonzalez, J. (J.), Bednarek, W. (W.), Bellizzi, L. K. (L. K.), Bernardini, E. (E.), Berti, A. (A.), Besenrieder, J. (J.), Bhattacharyya, W. (W.), Bigongiari, C. (C.), Biland, A. (A.), Blanch, O. (O.), Bonnoli, G. (G.), Bosnjak, Z. (Z.), Busetto, G. (G.), Carosi, R. (R.), Ceribella, G. (G.), Cerruti, M. (M.), Chai, Y. (Y.), Chilingarian, A. (A.), Cikota, S. (S.), Colak, S. M. (S. M.), Colin, U. (U.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), D'Elia, V. (V), Da Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Del Puppo, F. (F.), Delfino, M. (M.), Delgado, J. (J.), Depaoli, D. (D.), Di Pierro, F. (F.), Di Venere, L. (L.), Do Souto Espineira, E. (E.), Prester, D. D. (D. Dominis), Donini, A. (A.), Dorner, D. (D.), Doro, M. (M.), Elsaesser, D. (D.), Ramazani, V. F. (V. Fallah), Fattorini, A. (A.), Ferrara, G. (G.), Foffano, L. (L.), Fonseca, M. V. (M., V), Font, L. (L.), Fruck, C. (C.), Fukami, S. (S.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gasparyan, S. (S.), Gaug, M. (M.), Giglietto, N. (N.), Giordano, F. (F.), Gliwny, P. (P.), Godinovic, N. (N.), Green, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Hassan, T. (T.), Herrera, J. (J.), Hoang, J. (J.), Hrupec, D. (D.), Huetten, M. (M.), Inada, T. (T.), Inoue, S. (S.), Ishio, K. (K.), Iwamura, Y. (Y.), Jouvin, L. (L.), Kajiwara, Y. (Y.), Kerszberg, D. (D.), Kobayashi, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Lamastra, A. (A.), Lelas, D. (D.), Leone, F. (F.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Lopez-Coto, R. (R.), Lopez-Oramas, A. (A.), Loporchio, S. (S.), Machado de Oliveira Fraga, B. (B.), Maggio, C. (C.), Majumdar, P. (P.), Makariev, M. (M.), Mallamaci, M. (M.), Maneva, G. (G.), Manganaro, M. (M.), Mannheim, K. (K.), Maraschi, L. (L.), Mariotti, M. (M.), Martinez, M. (M.), Mazin, D. (D.), Mender, S. (S.), Micanovic, S. (S.), Miceli, D. (D.), Miener, T. (T.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Molina, E. (E.), Moralejo, A. (A.), Morcuende, D. (D.), Moreno, V. (V), Moretti, E. (E.), Munar-Adrover, P. (P.), Neustroev, V. (V), Nigro, C. (C.), Nilsson, K. (K.), Ninci, D. (D.), Nishijima, K. (K.), Noda, K. (K.), Nogues, L. (L.), Nozaki, S. (S.), Ohtani, Y. (Y.), Oka, T. (T.), Otero-Santos, J. (J.), Palatiello, M. (M.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Pavletic, L. (L.), Penil, P. (P.), Peresano, M. (M.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Puljak, I. (I), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saha, L. (L.), Sahakyan, N. (N.), Saito, T. (T.), Sakurai, S. (S.), Satalecka, K. (K.), Schleicher, B. (B.), Schmidt, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I), Sobczynska, D. (D.), Spolon, A. (A.), Stamerra, A. (A.), Strom, D. (D.), Strzys, M. (M.), Suda, Y. (Y.), Suric, T. (T.), Takahashi, M. (M.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Tosti, L. (L.), van Scherpenberg, J. (J.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Ventura, S. (S.), Verguilov, V. (V.), Vigorito, C. F. (C. F.), Vitale, V. (V.), Vovk, I. (I), Will, M. (M.), Zaric, D. (D.), Petropoulou, M. (M.), Finke, J. (J.), D'Ammando, F. (F.), Balokovi, M. (M.), Madejskic, G. (G.), Mori, K. (K.), Puccetti, S. (Simonetta), Leto, C. (C.), Perri, M. (M.), Verrecchia, F. (F.), Villata, M. (M.), Raiteri, C. M. (C. M.), Agudo, I. (I), Bachev, R. (R.), Berdyugin, A. (A.), Blinov, D. A. (D. A.), Chanishvili, R. (R.), Chen, W. P. (W. P.), Chigladze, R. (R.), Damljanovic, G. (G.), Eswaraiah, C. (C.), Grishina, T. S. (T. S.), Ibryamov, S. (S.), Jordan, B. (B.), Jorstad, S. G. (S. G.), Joshi, M. (M.), Kopatskaya, E. N. (E. N.), Kurtanidze, O. M. (O. M.), Kurtanidze, S. O. (S. O.), Larionova, E. G. (E. G.), Larionova, L. V. (L., V), Larionov, V. M. (V. M.), Latev, G. (G.), Lin, H. C. (H. C.), Marscher, A. P. (A. P.), Mokrushina, A. A. (A. A.), Morozova, D. A. (D. A.), Nikolashvili, M. G. (M. G.), Semkov, E. (E.), Smith, P. S. (P. S.), Strigachev, A. (A.), Troitskaya, Y. V. (Yu, V), Troitsky, I. S. (I. S.), Vince, O. (O.), Barnes, J. (J.), Guver, T. (T.), Moody, J. W. (J. W.), Sadun, A. C. (A. C.), Hovatta, T. (T.), Richards, J. L. (J. L.), Max-Moerbeck, W. (W.), Readhead, A. C. (A. C. S.), Lahteenmaki, A. (A.), Tornikoski, M. (M.), Tammi, J. (J.), Ramakrishnan, V. (V), and Reinthal, R. (R.)
Abstract: We report on a multiband variability and correlation study of the TeV blazar Mrk 421 during an exceptional flaring activity observed from 2013 April 11 to 19. The study uses, among others, data from GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT), Swift, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Large Area Telescope, Very Energetic Radiation Imaging Telescope Array System (VERITAS), and Major Atmospheric Gamma Imaging Cherenkov (MAGIC). The large blazar activity and the 43 hr of simultaneous NuSTAR and MAGIC/VERITAS observations permitted variability studies on 15 minute time bins over three X-ray bands (3–7 keV, 7–30 keV, and 30–80 keV) and three very-high-energy (VHE; >0.1 TeV) gamma-ray bands (0.2–0.4 TeV, 0.4–0.8 TeV, and >0.8 TeV). We detected substantial flux variations on multi-hour and sub-hour timescales in all of the X-ray and VHE gamma-ray bands. The characteristics of the sub-hour flux variations are essentially energy independent, while the multi-hour flux variations can have a strong dependence on the energy of the X-rays and the VHE gamma-rays. The three VHE bands and the three X-ray bands are positively correlated with no time lag, but the strength and characteristics of the correlation change substantially over time and across energy bands. Our findings favor multi-zone scenarios for explaining the achromatic/chromatic variability of the fast/slow components of the light curves, as well as the changes in the flux–flux correlation on day-long timescales. We interpret these results within a magnetic reconnection scenario, where the multi-hour flux variations are dominated by the combined emission from various plasmoids of different sizes and velocities, while the sub-hour flux variations are dominated by the emission from a single small plasmoid moving across the magnetic reconnection layer.
Published: 2020

49. Unraveling the Complex Behavior of Mrk 421 with Simultaneous X-Ray and VHE Observations during an Extreme Flaring Activity in 2013 April

Author: Federal Ministry of Education and Research (Germany), Istituto Nazionale di Astrofisica, Swiss National Science Foundation, Istituto Nazionale di Fisica Nucleare, Ministerio de Economía y Competitividad (España), European Commission, Department of Atomic Energy (India), Ministry of Education, Culture, Sports, Science and Technology (Japan), Japan Society for the Promotion of Science, Ministry of Education, Youth and Science (Bulgaria), Academy of Finland, Croatian Science Foundation, University of Rijeka, German Research Foundation, National Centre for Research and Development (Poland), Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, National Aeronautics and Space Administration (US), Department of Energy (US), Centre National de la Recherche Scientifique (France), Russian Science Foundation, Gordon and Betty Moore Foundation, John Templeton Foundation, Shota Rustaveli National Science Foundation, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Acciari, Victor, Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babić, A., Banerjee, B., Barres de Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, Wlodek, Palatiello, M., Max-Moerbeck, W., MAGIC Collaboration, Readhead, A. C. S., Lähteenmäki, Anne, Tornikoski, Merja, Tammi, J., Martínez, M., Ramakrishnan, V., Ishio, K., Do Souto Espiñeira, E., Reinthal, R., Cerruti, Matteo, Paneque, D., Chai, Y., Chilingarian, A., Fattorini, A., Cikota, S., Colak, S.M., Colin, U., Colombo, E., Sitarek, J., Peresano, M., Contreras, J.L., Mazin, D., Cortina, J., Paoletti, R., Covino, Stefano, D'Elia, V., Da Vela, Paolo, Ferrara, G., Dazzi, F., Maneva, G., de Angelis, A., Mannheim, K., de Lotto, B., Del Puppo, F., Delfino, M., Delgado, J., Paredes, Josep M., Mender, S., Depaoli, D., Foffano, L., Šnidarić, I., Fonseca, M.V., Font, L., Iwamura, Y., Fruck, Christian, Fukami, S., García López, R. J., Garczarczyk, M., Gasparyan, S., Pavletić, L., Finke, J., Sobczynska, D., Miceli, D., Gaug, Markus, Giglietto, N., Jouvin, L., Giordano, F., Gliwny, P., Godinović, N., Green, D., Hadasch, D., Hahn, A., Spolon, A., Peñil, P., Hassan, T., Baloković, M., Kajiwara, Y., Kerszberg, Daniel, Miener, T., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Stamerra, A., Kurtanidze, S.O., Perri, M., Lelas, D., Leone, F., Lindfors, E., Madejski, G., Lombardi, S., Longo, F., López, M., Minev, M., Bigongiari, C., López-Coto, R., Busetto, G., López-Oramas, A., di Pierro, F., Loporchio, S., Machado de Oliveira Fraga, B., Maggio, C., Majumdar, P., Mori, K., Makariev, M., Strom, D., Mallamaci, M., Miranda, J. M., Larionova, Elena G., Mirzoyan, R., Molina, E., Persic, M., Moralejo, A., Morcuende, D., Moreno, Vicente, Moretti, E., Marscher, Alan P., Munar-Adrover, P., Puccetti, Simonetta, Bernardini, E., Larionova, Liyudmila V., Neustroev, V., Nigro, C., Nilsson, Kari, Moroni, P. G. Prada, Ninci, D., Nishijima, K., D'Ammando, F., Noda, K., Nogués, L., Nozaki, S., Ohtani, Y., Larionov, Valeri M., Leto, C., Oka, T., Besenrieder, J., Prandini, E., Puljak, I., Strzys, M., Rhode, W., Ribó, Marc, Rico, J., Righi, C., Rugliancich, A., Latev, G., di Venere, L., Bonnoli, G., Saha, L., Sahakyan, N., Suda, Y., Saito, T., Bhattacharyya, W., Sakurai, S., Satalecka, K., Schleicher, B., Schmidt, K., Lin, H. C., Schweizer, T., Prester, D. Dominis, Surić, T., Takahashi, M., Verrecchia, F., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Herrera, J., Ramazani, V. Fallah, Torres-Albà, N., Biland, A., Tosti, L., Donini, A., van Scherpenberg, J., Vanzo, G., Vázquez Acosta, M., Villata, M., Ventura, S., Bellizzi, L. K., Verguilov, V., Berti, A., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Dorner, D., Blanch, O., Zarić, D., Raiteri, C.M., Hoang, J., Agudo, Iván, Bachev, R., Mokrushina, A. A., Berdyugin, A., Blinov, D.A., Chanishvili, R., Chen, W. P., Chigladze, R., Doro, M., Manganaro, M., Hrupec, D., Bošnjak, Ž., Damljanovic, G., Eswaraiah, C., Morozova, D.A., Grishina, T.S., Ibryamov, S., Jordan, B., Jorstad, S.G., Joshi, M., Kopatskaya, Evgenia N., Hütten, M., Elsaesser, D., Kurtanidze, O.M., Maraschi, L., Nikolashvili, M.G., Semkov, E., Carosi, R., Smith, P. S., Strigachev, A., Troitskaya, Yu. V., Troitsky, I. S., Inada, T., Otero-Santos, J., Mićanović, S., Vince, O., Barnes, J., Güver, T., Mariotti, M., Moody, J.W., Sadun, A. C., Hovatta, T., Ceribella, G., Inoue, S., Richards, J. L., Federal Ministry of Education and Research (Germany), Istituto Nazionale di Astrofisica, Swiss National Science Foundation, Istituto Nazionale di Fisica Nucleare, Ministerio de Economía y Competitividad (España), European Commission, Department of Atomic Energy (India), Ministry of Education, Culture, Sports, Science and Technology (Japan), Japan Society for the Promotion of Science, Ministry of Education, Youth and Science (Bulgaria), Academy of Finland, Croatian Science Foundation, University of Rijeka, German Research Foundation, National Centre for Research and Development (Poland), Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, National Aeronautics and Space Administration (US), Department of Energy (US), Centre National de la Recherche Scientifique (France), Russian Science Foundation, Gordon and Betty Moore Foundation, John Templeton Foundation, Shota Rustaveli National Science Foundation, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Acciari, Victor, Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babić, A., Banerjee, B., Barres de Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, Wlodek, Palatiello, M., Max-Moerbeck, W., MAGIC Collaboration, Readhead, A. C. S., Lähteenmäki, Anne, Tornikoski, Merja, Tammi, J., Martínez, M., Ramakrishnan, V., Ishio, K., Do Souto Espiñeira, E., Reinthal, R., Cerruti, Matteo, Paneque, D., Chai, Y., Chilingarian, A., Fattorini, A., Cikota, S., Colak, S.M., Colin, U., Colombo, E., Sitarek, J., Peresano, M., Contreras, J.L., Mazin, D., Cortina, J., Paoletti, R., Covino, Stefano, D'Elia, V., Da Vela, Paolo, Ferrara, G., Dazzi, F., Maneva, G., de Angelis, A., Mannheim, K., de Lotto, B., Del Puppo, F., Delfino, M., Delgado, J., Paredes, Josep M., Mender, S., Depaoli, D., Foffano, L., Šnidarić, I., Fonseca, M.V., Font, L., Iwamura, Y., Fruck, Christian, Fukami, S., García López, R. J., Garczarczyk, M., Gasparyan, S., Pavletić, L., Finke, J., Sobczynska, D., Miceli, D., Gaug, Markus, Giglietto, N., Jouvin, L., Giordano, F., Gliwny, P., Godinović, N., Green, D., Hadasch, D., Hahn, A., Spolon, A., Peñil, P., Hassan, T., Baloković, M., Kajiwara, Y., Kerszberg, Daniel, Miener, T., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Stamerra, A., Kurtanidze, S.O., Perri, M., Lelas, D., Leone, F., Lindfors, E., Madejski, G., Lombardi, S., Longo, F., López, M., Minev, M., Bigongiari, C., López-Coto, R., Busetto, G., López-Oramas, A., di Pierro, F., Loporchio, S., Machado de Oliveira Fraga, B., Maggio, C., Majumdar, P., Mori, K., Makariev, M., Strom, D., Mallamaci, M., Miranda, J. M., Larionova, Elena G., Mirzoyan, R., Molina, E., Persic, M., Moralejo, A., Morcuende, D., Moreno, Vicente, Moretti, E., Marscher, Alan P., Munar-Adrover, P., Puccetti, Simonetta, Bernardini, E., Larionova, Liyudmila V., Neustroev, V., Nigro, C., Nilsson, Kari, Moroni, P. G. 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Abstract: We report on a multiband variability and correlation study of the TeV blazar Mrk 421 during an exceptional flaring activity observed from 2013 April 11 to 19. The study uses, among others, data from GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT), Swift, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Large Area Telescope, Very Energetic Radiation Imaging Telescope Array System (VERITAS), and Major Atmospheric Gamma Imaging Cherenkov (MAGIC). The large blazar activity and the 43 hr of simultaneous NuSTAR and MAGIC/VERITAS observations permitted variability studies on 15 minute time bins over three X-ray bands (3-7 keV, 7-30 keV, and 30-80 keV) and three very-high-energy (VHE; >0.1 TeV) gamma-ray bands (0.2-0.4 TeV, 0.4-0.8 TeV, and >0.8 TeV). We detected substantial flux variations on multi-hour and sub-hour timescales in all of the X-ray and VHE gamma-ray bands. The characteristics of the sub-hour flux variations are essentially energy independent, while the multi-hour flux variations can have a strong dependence on the energy of the X-rays and the VHE gamma-rays. The three VHE bands and the three X-ray bands are positively correlated with no time lag, but the strength and characteristics of the correlation change substantially over time and across energy bands. Our findings favor multi-zone scenarios for explaining the achromatic/chromatic variability of the fast/slow components of the light curves, as well as the changes in the flux-flux correlation on day-long timescales. We interpret these results within a magnetic reconnection scenario, where the multi-hour flux variations are dominated by the combined emission from various plasmoids of different sizes and velocities, while the sub-hour flux variations are dominated by the emission from a single small plasmoid moving across the magnetic reconnection layer. © 2020. The American Astronomical Society. All rights reserved.
Published: 2020

50. Relativistic dynamics of expanding sources

Author: Sadun, A. C. and Sadun, L. A.
Published: 1991
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