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1. 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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2. The detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Author: MAGIC Collaboration, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Baack, D., Babić, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., Bednarek, W., Bernardini, E., Berse, R. Ch., Berti, A., Bhattacharyya, W., Biland, A., Blanch, O., Bonnoli, G., Carosi, R., Carosi, A., Ceribella, G., 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., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Elsaesser, D., 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., dić, D. Kuvež, Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., Maggio, C., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Mielke, K., 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., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takahashi, M., 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., González, J. Becerra, Tanaka, Y., Ojha, R., Finke, J., Lähteenmäki, A., Järvelä, E., Tornikoski, M., Ramakrishnan, V., Hovatta, T., Jorstad, S. G., Marscher, A. P., Larionov, V. M., Borman, G. A., Grishina, T. S., Kopatskaya, E. N., Larionova, L. V., Morozova, D. A., Savchenko, S. S., Troitskaya, Yu. V., Troitsky, I. S., Vasilyev, A. A., Agudo, I., Molina, S. N., Casadio, C., Gurwell, M., Carnerero, M. I., Protasio, C., and Pulido, J. A Acosta
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The very-high-energy (VHE, $\gtrsim 100$ GeV) $\gamma$-ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z=0.368 or z$\geqslant$0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. We investigate the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and put it in context with possible emission scenarios. We collect photometric data in radio, optical, X-ray, and $\gamma$ ray. We study both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy $\gamma$ ray\ (HE, 100 MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100$^\circ$. (...) The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars, i.e. inverse Compton scattering on an external soft photon field from the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to flat spectrum radio quasars (FSRQs) and low-frequency peaked BL Lac objects (LBL)., Comment: 15 pages, 7 figures, submitted to A&A
Published: 2018
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3. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

Author: MAGIC Collaboration, 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., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carosi, R., Carosi, A., Chatterjee, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Cumani, P., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Wilhelmi, E. de Oña, 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., 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., Hughes, G., Ishio, K., Konno, Y., Kubo, H., Kushida, J., Kuveždić, D., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Noda, K., Nogués, L., 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., Garcia, J. R., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Saito, T., Satalecka, K., Schroeder, S., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Torres, D. F., Torres-Albà, N., Toyama, T., Treves, A., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zarić, D., Desiante, R., D'Ammando, F., Larsson, S., Raiteri, C. M., Reinthal, R., Lähteenmäki, A., Järvelä, E., Tornikoski, M., Ramakrishnan, V., Jorstad, S. G., Marscher, A. P., Bala, V., MacDonald, N. R., Kaur, N., Sameer, Baliyan, K., Acosta-Pulido, J. A., Lazaro, C., Martínez-Lombilla, C., Grinon-Marin, A. B., Yabar, A. Pastor, Protasio, C., Carnerero, M. I., Jermak, H., Steele, I. A., Larionov, V. M., Borman, G. A., and Grishina, T. S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. PKS 1510-089 is one of only a few flat spectrum radio quasars detected in the VHE (very-high-energy, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510-089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510-089 with the MAGIC telescopes during a long high gamma-ray state in May 2015. In order to perform broadband modelling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510-089 has been detected by MAGIC during a few day-long observations performed in the middle of a long, high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. However, due to large uncertainty on the knot separation time, the association with the VHE gamma-ray emission cannot be firmly established. The spectral shape in the VHE band during the flare is similar to the ones obtained during previous measurements of the source. The observed flux variability sets for the first time constraints on the size of the region from which VHE gamma rays are emitted. We model the broadband SED in the framework of the external Compton scenario and discuss the possible emission site in view of multiwavelength data and alternative emission models., Comment: 12 pages, 10 figures, accepted for a publication in A&A
Published: 2016
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4. 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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5. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Baack, D., Babić, A., Banerjee, B., Bangale, P., Barres De Almeida, U., Barrio, J. A., Bednarek, W., Bernardini, E., Berse, R. Ch., Berti, A., Bhattacharyya, W., Biland, A., Blanch, O., Bonnoli, G., Carosi, R., Carosi, A., Ceribella, G., 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., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fallah Ramazani, V., Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., García López, R. J., 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., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Mielke, K., Minev, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moreno, V., Moretti, E., Nagayoshi, T., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Paiano, S., Palacio, J., Paneque, D., Paoletti, R., Paredes, J. M., Pedaletti, Giovanna, Peresano, M., Persic, M., Prada Moroni, P. G., Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takahashi, M., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Treves, A., Tsujimoto, S., Vanzo, G., Vazquez Acosta, M., Vovk, I., Ward, J. E., Will, M., Zarić, D., Becerra Gonzalez, Josefa, Tanaka, Y., Ojha, R., Finke, J., Lähteenmäki, A., Järvelä, E., Tornikoski, M., Ramakrishnan, V., Hovatta, T., Jorstad, S. G., Marscher, A. P., Larionov, V. M., Borman, G. A., Grishina, T. S., Kopatskaya, E. N., Larionova, L. V., Morozova, D. A., Savchenko, S. S., Troitskaya, Yu. V., Troitsky, I. S., Vasilyev, A. A., Agudo, I., Molina, S. N., Casadio, C., Gurwell, M., Carnerero, M. I., Protasio, C., and Acosta Pulido, J. A.
Abstract: Astronomy and astrophysics 617, A30 (2018). doi:10.1051/0004-6361/201832624, ims.The very high energy (VHE&100GeV)γ-ray MAGIC observations of the blazar S4 0954+65, were triggered by anexceptionally high flux state of emission in the optical. This blazar has a disputed redshift ofz= 0.368 orz>0.45 and an uncertainclassification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understandphysical processes in the jet of S4 0954+65 and thus contribute to its classification.Methods.We investigated the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazarduring an enhanced state in February 2015 and have put it in context with possible emission scenarios. We collected photometric datain radio, optical, X-ray, andγ-ray. We studied both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data.Results.Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data withFermi-LAT at high energyγ-ray(HE, 100 MeV, Published by EDP Sciences, Les Ulis
Published: 2018
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6. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Author: Ahnen, M. L. (M. L.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Arcaro, C. (C.), Baack, D. (D.), Babic, A. (A.), Banerjee, B. (B.), Bangale, P. (P.), Barres de Almeida, U. (U.), Barrio, J. A. (J. A.), Bednarek, W. (W.), Bernardini, E. (E.), Berse, R. C. (R. Ch.), Berti, A. (A.), Bhattacharyya, W. (W.), Biland, A. (A.), Blanch, O. (O.), Bonnoli, G. (G.), Carosi, R. (R.), Carosi, A. (A.), Ceribella, G. (G.), Chatterjee, A. (A.), Colak, S. M. (S. M.), Colin, P. (P.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), Cumani, P. (P.), Da Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Delfino, M. (M.), Delgado, J. (J.), Di Pierro, F. (F.), Dominguez, A. (A.), Prester, D. D. (D. Dominis), Dorner, D. (D.), Doro, M. (M.), Einecke, S. (S.), Elsaesser, D. (D.), Ramazani, V. F. (V. Fallah), Fernandez-Barral, A. (A.), Fidalgo, D. (D.), Fonseca, M. V. (M. V.), Font, L. (L.), Fruck, C. (C.), Galindo, D. (D.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gaug, M. (M.), Giammaria, P. (P.), Godinovic, N. (N.), Gora, D. (D.), Guberman, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Hassan, T. (T.), Hayashida, M. (M.), Herrera, J. (J.), Hose, J. (J.), Hrupec, D. (D.), Ishio, K. (K.), Konno, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Kuvezdic, D. (D.), Lelas, D. (D.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Maggio, C. (C.), Majumdar, P. (P.), Makariev, 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.), Mielke, K. (K.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Moralejo, A. (A.), Moreno, V. (V.), Moretti, E. (E.), Nagayoshi, T. (T.), 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.), Paiano, S. (S.), Palacio, J. (J.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Pedaletti, G. (G.), Peresano, M. (M.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Puljak, I. (I.), Garcia, J. R. (J. R.), Reichardt, I. (I.), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saito, T. (T.), Satalecka, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I.), Sobczynska, D. (D.), Stamerra, A. (A.), Strzys, M. (M.), Suric, T. (T.), Takahashi, M. (M.), Takalo, L. (L.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Treves, A. (A.), Tsujimoto, S. (S.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Vovk, I. (I.), Ward, J. E. (J. E.), Will, M. (M.), Zaric, D. (D.), Becerra Gonzalez, J. (J.), Tanaka, Y. (Y.), Ojha, R. (R.), Finke, J. (J.), Lahteenmaki, A. (A.), Jarvela, E. (E.), Tornikoski, M. (M.), Ramakrishnan, V. (V.), Hovatta, T. (T.), Jorstad, S. G. (S. G.), Marscher, A. P. (A. P.), Larionov, V. M. (V. M.), Borman, G. A. (G. A.), Grishina, T. S. (T. S.), Kopatskaya, E. N. (E. N.), Larionova, L. V. (L. V.), Morozova, D. A. (D. A.), Savchenko, S. S. (S. S.), Troitskaya, Y. V. (Yu. V.), Troitsky, I. S. (I. S.), Vasilyev, A. A. (A. A.), Agudo, I. (I.), Molina, S. N. (S. N.), Casadio, C. (C.), Gurwell, M. (M.), Carnerero, M. I. (M. I.), Protasio, C. (C.), Acosta Pulido, J. A. (J. A.), Ahnen, M. L. (M. L.), Ansoldi, S. (S.), Antonelli, L. A. (L. A.), Arcaro, C. (C.), Baack, D. (D.), Babic, A. (A.), Banerjee, B. (B.), Bangale, P. (P.), Barres de Almeida, U. (U.), Barrio, J. A. (J. A.), Bednarek, W. (W.), Bernardini, E. (E.), Berse, R. C. (R. Ch.), Berti, A. (A.), Bhattacharyya, W. (W.), Biland, A. (A.), Blanch, O. (O.), Bonnoli, G. (G.), Carosi, R. (R.), Carosi, A. (A.), Ceribella, G. (G.), Chatterjee, A. (A.), Colak, S. M. (S. M.), Colin, P. (P.), Colombo, E. (E.), Contreras, J. L. (J. L.), Cortina, J. (J.), Covino, S. (S.), Cumani, P. (P.), Da Vela, P. (P.), Dazzi, F. (F.), De Angelis, A. (A.), De Lotto, B. (B.), Delfino, M. (M.), Delgado, J. (J.), Di Pierro, F. (F.), Dominguez, A. (A.), Prester, D. D. (D. Dominis), Dorner, D. (D.), Doro, M. (M.), Einecke, S. (S.), Elsaesser, D. (D.), Ramazani, V. F. (V. Fallah), Fernandez-Barral, A. (A.), Fidalgo, D. (D.), Fonseca, M. V. (M. V.), Font, L. (L.), Fruck, C. (C.), Galindo, D. (D.), Garcia Lopez, R. J. (R. J.), Garczarczyk, M. (M.), Gaug, M. (M.), Giammaria, P. (P.), Godinovic, N. (N.), Gora, D. (D.), Guberman, D. (D.), Hadasch, D. (D.), Hahn, A. (A.), Hassan, T. (T.), Hayashida, M. (M.), Herrera, J. (J.), Hose, J. (J.), Hrupec, D. (D.), Ishio, K. (K.), Konno, Y. (Y.), Kubo, H. (H.), Kushida, J. (J.), Kuvezdic, D. (D.), Lelas, D. (D.), Lindfors, E. (E.), Lombardi, S. (S.), Longo, F. (F.), Lopez, M. (M.), Maggio, C. (C.), Majumdar, P. (P.), Makariev, 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.), Mielke, K. (K.), Minev, M. (M.), Miranda, J. M. (J. M.), Mirzoyan, R. (R.), Moralejo, A. (A.), Moreno, V. (V.), Moretti, E. (E.), Nagayoshi, T. (T.), 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.), Paiano, S. (S.), Palacio, J. (J.), Paneque, D. (D.), Paoletti, R. (R.), Paredes, J. M. (J. M.), Pedaletti, G. (G.), Peresano, M. (M.), Persic, M. (M.), Moroni, P. G. (P. G. Prada), Prandini, E. (E.), Puljak, I. (I.), Garcia, J. R. (J. R.), Reichardt, I. (I.), Rhode, W. (W.), Ribo, M. (M.), Rico, J. (J.), Righi, C. (C.), Rugliancich, A. (A.), Saito, T. (T.), Satalecka, K. (K.), Schweizer, T. (T.), Sitarek, J. (J.), Snidaric, I. (I.), Sobczynska, D. (D.), Stamerra, A. (A.), Strzys, M. (M.), Suric, T. (T.), Takahashi, M. (M.), Takalo, L. (L.), Tavecchio, F. (F.), Temnikov, P. (P.), Terzic, T. (T.), Teshima, M. (M.), Torres-Alba, N. (N.), Treves, A. (A.), Tsujimoto, S. (S.), Vanzo, G. (G.), Vazquez Acosta, M. (M.), Vovk, I. (I.), Ward, J. E. (J. E.), Will, M. (M.), Zaric, D. (D.), Becerra Gonzalez, J. (J.), Tanaka, Y. (Y.), Ojha, R. (R.), Finke, J. (J.), Lahteenmaki, A. (A.), Jarvela, E. (E.), Tornikoski, M. (M.), Ramakrishnan, V. (V.), Hovatta, T. (T.), Jorstad, S. G. (S. G.), Marscher, A. P. (A. P.), Larionov, V. M. (V. M.), Borman, G. A. (G. A.), Grishina, T. S. (T. S.), Kopatskaya, E. N. (E. N.), Larionova, L. V. (L. V.), Morozova, D. A. (D. A.), Savchenko, S. S. (S. S.), Troitskaya, Y. V. (Yu. V.), Troitsky, I. S. (I. S.), Vasilyev, A. A. (A. A.), Agudo, I. (I.), Molina, S. N. (S. N.), Casadio, C. (C.), Gurwell, M. (M.), Carnerero, M. I. (M. I.), Protasio, C. (C.), and Acosta Pulido, J. A. (J. A.)
Abstract: Aims: The very high energy (VHE ≳100 GeV) γ-ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z = 0.368 or z ≥ 0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. Methods: We investigated the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and have put it in context with possible emission scenarios. We collected photometric data in radio, optical, X-ray, and γ-ray. We studied both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Results: Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy γ-ray (HE, 100 MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100°. Conclusions: The high emission state during the flare allows us to compile the simultaneous broadband SED and to characterize it in the scope of blazar jet emission models. The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars (FSRQs), that is, inverse Compton scattering on an external soft photon fieldfrom the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to FSRQs and low-frequency peaked BL Lac objects
Published: 2018

7. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Author: Ministerio de Economía y Competitividad (España), Swiss National Science Foundation, Federal Ministry of Education and Research (Germany), Junta de Andalucía, Max Planck Society, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Baack, D., Babi¿, A., Banerjee, B., Bangale, P., Barres de Almeida, U., Barrio, J. A., Bednarek, Wlodek, Larionova, Liyudmila V., García López, R. J., Vasilyev, A. A., Paoletti, R., Agudo, Iván, Dominis Prester, D., Paiano, S., Makariev, M., Molina, Sol, Schweizer, T., Majumdar, P., Casadio, Carolina, Gurwell, M., Carnerero, M. I., Ishio, K., Kuveždi¿, D., Protasio, C., Ceribella, G., Bonnoli, G., Konno, Y., Chatterjee, A., Satalecka, K., Colak, S.M., Godinović, N., Rugliancich, A., Moralejo, A., Colin, P., Tsujimoto, S., Colombo, E., Contreras, J.L., Cortina, J., Manganaro, M., Mariotti, M., Covino, Stefano, Dorner, D., di Pierro, F., Mannheim, K., Nogués, L., Doro, M., Lelas, D., Teshima, M., Noda, K., Einecke, S., Biland, A., Elsaesser, D., Fallah Ramazani, V., Fernández-Barral, Asunción, Moreno, Vicente, Fidalgo, Darío, Gora, D., Gaug, Markus, Moretti, E., Righi, C., Guberman, D., Martínez, M., Lähteenmäki, Anne, Rico, J., Hadasch, D., Hahn, A., Hassan, T., Palacio, J., Peresano, M., Hayashida, M., Paneque, D., Kushida, J., Persic, M., Terzi¿, T., Lindfors, E., Blanch, O., Temnikov, P., Lombardi, S., Longo, F., López, M., Saito, T., Šnidari¿, I., Maggio, C., Berse, R. Ch., Maraschi, L., Finke, J., Masuda, S., Delgado, J., Ojha, R., Mazin, D., Mielke, K., Minev, M., Torres-Albà, N., Vázquez Acosta, M., Miranda, J. M., Nagayoshi, T., Mirzoyan, R., Treves, A., Neustroev, V., Delfino, M., Niedzwiecki, A., Sobczynska, D., Dazzi, F., Morozova, D.A., Nievas Rosillo, M., Garczarczyk, M., Nigro, C., Nilsson, Kari, Ninci, D., Järvelä, E., Hovatta, T., Nishijima, K., Prada Moroni, P. G., Pedaletti, G., Tornikoski, Merja, Bernardini, E., Prandini, E., Vovk, I., Fruck, Christian, Acosta-Pulido, J. A., Puljak, I., Kubo, H., García, J. R, Reichardt, I., Rhode, W., Savchenko, S. S., Ribó, Marc, Stamerra, A., Sitarek, J., Troitskaya, Yu. V., Da Vela, Paolo, Strzys, M., Jorstad, S.G., Hrupec, D., Cumani, P., Surić, T., Takahashi, M., Takalo, L., Berti, A., Carosi, R., Tavecchio, F., Bhattacharyya, W., Vanzo, G., Carosi, A., Font, L., Ward, J. E., Maneva, G., Fonseca, M.V., Will, M., Zari¿, D., Becerra González, J., de Angelis, A., Domínguez, A., Tanaka, Y., de Lotto, B., Ramakrishnan, V., Hose, J., Marscher, Alan P., Paredes, Josep M., Herrera, J., Larionov, Valeri M., Borman, G.A., Grishina, T.S., Galindo, D., Giammaria, P., Kopatskaya, Evgenia N., Troitsky, I. S., Ministerio de Economía y Competitividad (España), Swiss National Science Foundation, Federal Ministry of Education and Research (Germany), Junta de Andalucía, Max Planck Society, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Baack, D., Babi¿, A., Banerjee, B., Bangale, P., Barres de Almeida, U., Barrio, J. A., Bednarek, Wlodek, Larionova, Liyudmila V., García López, R. J., Vasilyev, A. A., Paoletti, R., Agudo, Iván, Dominis Prester, D., Paiano, S., Makariev, M., Molina, Sol, Schweizer, T., Majumdar, P., Casadio, Carolina, Gurwell, M., Carnerero, M. I., Ishio, K., Kuveždi¿, D., Protasio, C., Ceribella, G., Bonnoli, G., Konno, Y., Chatterjee, A., Satalecka, K., Colak, S.M., Godinović, N., Rugliancich, A., Moralejo, A., Colin, P., Tsujimoto, S., Colombo, E., Contreras, J.L., Cortina, J., Manganaro, M., Mariotti, M., Covino, Stefano, Dorner, D., di Pierro, F., Mannheim, K., Nogués, L., Doro, M., Lelas, D., Teshima, M., Noda, K., Einecke, S., Biland, A., Elsaesser, D., Fallah Ramazani, V., Fernández-Barral, Asunción, Moreno, Vicente, Fidalgo, Darío, Gora, D., Gaug, Markus, Moretti, E., Righi, C., Guberman, D., Martínez, M., Lähteenmäki, Anne, Rico, J., Hadasch, D., Hahn, A., Hassan, T., Palacio, J., Peresano, M., Hayashida, M., Paneque, D., Kushida, J., Persic, M., Terzi¿, T., Lindfors, E., Blanch, O., Temnikov, P., Lombardi, S., Longo, F., López, M., Saito, T., Šnidari¿, I., Maggio, C., Berse, R. Ch., Maraschi, L., Finke, J., Masuda, S., Delgado, J., Ojha, R., Mazin, D., Mielke, K., Minev, M., Torres-Albà, N., Vázquez Acosta, M., Miranda, J. M., Nagayoshi, T., Mirzoyan, R., Treves, A., Neustroev, V., Delfino, M., Niedzwiecki, A., Sobczynska, D., Dazzi, F., Morozova, D.A., Nievas Rosillo, M., Garczarczyk, M., Nigro, C., Nilsson, Kari, Ninci, D., Järvelä, E., Hovatta, T., Nishijima, K., Prada Moroni, P. G., Pedaletti, G., Tornikoski, Merja, Bernardini, E., Prandini, E., Vovk, I., Fruck, Christian, Acosta-Pulido, J. A., Puljak, I., Kubo, H., García, J. R, Reichardt, I., Rhode, W., Savchenko, S. S., Ribó, Marc, Stamerra, A., Sitarek, J., Troitskaya, Yu. V., Da Vela, Paolo, Strzys, M., Jorstad, S.G., Hrupec, D., Cumani, P., Surić, T., Takahashi, M., Takalo, L., Berti, A., Carosi, R., Tavecchio, F., Bhattacharyya, W., Vanzo, G., Carosi, A., Font, L., Ward, J. E., Maneva, G., Fonseca, M.V., Will, M., Zari¿, D., Becerra González, J., de Angelis, A., Domínguez, A., Tanaka, Y., de Lotto, B., Ramakrishnan, V., Hose, J., Marscher, Alan P., Paredes, Josep M., Herrera, J., Larionov, Valeri M., Borman, G.A., Grishina, T.S., Galindo, D., Giammaria, P., Kopatskaya, Evgenia N., and Troitsky, I. S.
Abstract: The very high energy (VHE ¿ 100 GeV) -ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z = 0.368 or z ¿ 0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. Methods. We investigated the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and have put it in context with possible emission scenarios. We collected photometric data in radio, optical, X-ray, and ¿-ray. We studied both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Results. Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy ¿-ray(HE, 100 MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100. Conclusions. The high emission state during the flare allows us to compile the simultaneous broadband SED and to characterize it in the scope of blazar jet emission models. The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars (FSRQs), that is, inverse Compton scattering on an external soft photon field from the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to FSRQs and low-frequency peaked BL Lac objects (LBL). © ESO 2018.
Published: 2018

8. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510−089 in 2015

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Babić, A., Banerjee, B., Bangale, P., Barres De Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, W., Bernardini, E., Berti, A., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carosi, R., Carosi, A., Chatterjee, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Cumani, P., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., De Oña Wilhelmi, E., Di Pierro, F., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Eisenacher Glawion, D., Elsaesser, D., Engelkemeier, M., Fallah Ramazani, V., Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., García López, R. J., Garczarczyk, Markus, Gaug, M., Giammaria, P., Godinović, N., Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hassan, T., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Ishio, K., Konno, Y., Kushida, J., Kuveždić, D., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nilsson, K., Nishijima, K., Noda, K., Nogués, L., 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., Prada Moroni, P. G., Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Saito, T., Satalecka, K., Schroeder, S., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Torres, D. F., Torres-Albà, N., Toyama, T., Treves, A., Vanzo, G., Vazquez Acosta, M., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zarić, D., Desiante, R., D'Ammando, F., Larsson, S., Raiteri, C. M., Reinthal, R., Lähteenmäki, A., Järvelä, E., Tornikoski, M., Ramakrishnan, V., Jorstad, S. G., Marscher, A. P., Bala, V., MacDonald, N. R., Kaur, N., Sameer, Baliyan, K., Acosta-Pulido, J. A., Lazaro, C., Martínez-Lombilla, C., Grinon-Marin, A. B., Yabar, A. Pastor, Protasio, C., Carnerero, M. I., Jermak, H., Steele, I. A., Larionov, V. M., Borman, G. A., and Grishina, T. S.
Subjects: X-ray, flux, gamma ray: VHE, spectral, quasar, polarization: optical, rotation, MAGIC
Abstract: Astronomy and astrophysics 603, A29 (2017). doi:10.1051/0004-6361/201629960, Context. PKS 1510−089 is one of only a few flat spectrum radio quasars detected in the very-high-energy (VHE, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510−089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510−089 with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes during a long, high gamma-ray state in May 2015. In order to perform broadband modeling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray, and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510−089 was detected by MAGIC during a few day-long observations performed in the middle of a long, high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. However, owing to large uncertainty on the knot separation time, the association with the VHE gamma-ray emission cannot be firmly established. The spectral shape in the VHE band during the flare is similar to those obtained during previous measurements of the source. The observed flux variability sets constraints for the first time on the size of the region from which VHE gamma rays are emitted. We model the broadband SED in the framework of the external Compton scenario and discuss the possible emission site in view of multiwavelength data and alternative emission models. Key words: galaxies: active / galaxies: jets / gamma rays: galaxies / quasars: individual: PKS 1510-089, Published by EDP Sciences, Les Ulis
Published: 2017
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9. Blazar spectral variability as explained by a twisted inhomogeneous jet

Author: Raiteri C., Villata M., Acosta-Pulido J., Agudo I., Arkharov A., Bachev R., Baida G., Benítez E., Borman G., Boschin W., Bozhilov V., Butuzova M., Calcidese P., Carnerero M., Carosati D., Casadio C., Castro-Segura N., Chen W., Damljanovic G., D'Ammando F., Di Paola A., Echevarría J., Efimova N., Ehgamberdiev S., Espinosa C., Fuentes A., Giunta A., Gómez J., Grishina T., Gurwell M., Hiriart D., Jermak H., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Kuratov K., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionov V., Larionova E., Larionova L., Lázaro C., Lin C., Malmrose M., Marscher A., Matsumoto K., McBreen B., Michel R., Mihov B., Minev M., Mirzaqulov D., Mokrushina A., Molina S., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Okhmat D., Ovcharov E., Pinna F., Polakis T., Protasio C., Pursimo T., Redondo-Lorenzo F., Rizzi N., Rodriguez-Coira G., Sadakane K., Sadun A., Samal M., Savchenko S., Semkov E., Skiff B., Slavcheva-Mihova L., Smith P., and Steele I.
Subjects: Astrophysics::High Energy Astrophysical Phenomena
Abstract: © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions - such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution - can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing angle. The agreement between observations and theoretical predictions can be seen as further validation of the relativistic beaming theory.
Published: 2017

10. Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

Author: Carnerero, M. I., primary, Raiteri, C. M., additional, Villata, M., additional, Acosta-Pulido, J. A., additional, Larionov, V. M., additional, Smith, P. S., additional, D'Ammando, F., additional, Agudo, I., additional, Arévalo, M. J., additional, Bachev, R., additional, Barnes, J., additional, Boeva, S., additional, Bozhilov, V., additional, Carosati, D., additional, Casadio, C., additional, Chen, W. P., additional, Damljanovic, G., additional, Eswaraiah, E., additional, Forné, E., additional, Gantchev, G., additional, Gómez, J. L., additional, González-Morales, P. A., additional, Griñón-Marín, A. B., additional, Grishina, T. S., additional, Holden, M., additional, Ibryamov, S., additional, Joner, M. D., additional, Jordan, B., additional, Jorstad, S. G., additional, Joshi, M., additional, Kopatskaya, E. N., additional, Koptelova, E., additional, Kurtanidze, O. M., additional, Kurtanidze, S. O., additional, Larionova, E. G., additional, Larionova, L. V., additional, Latev, G., additional, Lázaro, C., additional, Ligustri, R., additional, Lin, H. C., additional, Marscher, A. P., additional, Martínez-Lombilla, C., additional, McBreen, B., additional, Mihov, B., additional, Molina, S. N., additional, Moody, J. W., additional, Morozova, D. A., additional, Nikolashvili, M. G., additional, Nilsson, K., additional, Ovcharov, E., additional, Pace, C., additional, Panwar, N., additional, Pastor Yabar, A., additional, Pearson, R. L., additional, Pinna, F., additional, Protasio, C., additional, Rizzi, N., additional, Redondo-Lorenzo, F. J., additional, Rodríguez-Coira, G., additional, Ros, J. A., additional, Sadun, A. C., additional, Savchenko, S. S., additional, Semkov, E., additional, Slavcheva-Mihova, L., additional, Smith, N., additional, Strigachev, A., additional, Troitskaya, Yu. V., additional, Troitsky, I. S., additional, Vasilyev, A. A., additional, and Vince, O., additional
Published: 2017
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11. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

Author: Raiteri, C. M., primary, Nicastro, F., additional, Stamerra, A., additional, Villata, M., additional, Larionov, V. M., additional, Blinov, D., additional, Acosta-Pulido, J. A., additional, Arévalo, M. J., additional, Arkharov, A. A., additional, Bachev, R., additional, Borman, G. A., additional, Carnerero, M. I., additional, Carosati, D., additional, Cecconi, M., additional, Chen, W.-P., additional, Damljanovic, G., additional, Di Paola, A., additional, Ehgamberdiev, Sh. A., additional, Frasca, A., additional, Giroletti, M., additional, González-Morales, P. A., additional, Griñon-Marín, A. B., additional, Grishina, T. S., additional, Huang, P.-C., additional, Ibryamov, S., additional, Klimanov, S. A., additional, Kopatskaya, E. N., additional, Kurtanidze, O. M., additional, Kurtanidze, S. O., additional, Lähteenmäki, A., additional, Larionova, E. G., additional, Larionova, L. V., additional, Lázaro, C., additional, Leto, G., additional, Liodakis, I., additional, Martínez-Lombilla, C., additional, Mihov, B., additional, Mirzaqulov, D. O., additional, Mokrushina, A. A., additional, Moody, J. W., additional, Morozova, D. A., additional, Nazarov, S. V., additional, Nikolashvili, M. G., additional, Ohlert, J. M., additional, Panopoulou, G. V., additional, Pastor Yabar, A., additional, Pinna, F., additional, Protasio, C., additional, Rizzi, N., additional, Sadun, A. C., additional, Savchenko, S. S., additional, Semkov, E., additional, Sigua, L. A., additional, Slavcheva-Mihova, L., additional, Strigachev, A., additional, Tornikoski, M., additional, Troitskaya, Yu. V., additional, Troitsky, I. S., additional, Vasilyev, A. A., additional, Vera, R. J. C., additional, Vince, O., additional, and Zanmar Sanchez, R., additional
Published: 2016
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12. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Babic, A., Banerjee, B., Bangale, P., De Almeida, U. Barres, Barrio, J. A., Bednarek, W., Bernardini, E., Berti, A., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carosi, R., Carosi, A., Chatterjee, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Cumani, P., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Wilhelmi, E. De Ona, Di Pierro, F., Doert, M., Dominguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Engelkemeier, M., Ramazani, V. Fallah, Fernandez-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Lopez, R. J. Garcia, Garczarczyk, M., Gaug, M., Giammaria, P., Godinovic, N., Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hassan, T., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Ishio, K., Konno, Y., Kubo, H., Kushida, J., Kuvezdic, D., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Mazin, D., Menzel, U., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Noda, K., Nogues, L., 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., Garcia, J. R., Reichardt, I., Rhode, W., Ribo, M., Rico, J., Saito, T., Satalecka, K., Schroeder, S., Schweizer, T., Shore, S. N., Sillanpaa, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Strzys, M., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzic, T., Tescaro, D., Teshima, M., Torres, D. F., Torres-Alba, N., Toyama, T., Treves, A., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zaric, D., Desiante, R., Gonzalez, J. Becerra, D'Ammando, F., Larsson, S., Raiteri, C. M., Reinthal, R., Lahteenmaki, A., Jarvela, E., Tornikoski, M., Ramakrishnan, V., Jorstad, S. G., Marscher, A. P., Bala, V., Macdonald, N. R., Kaur, N., Sameer, Baliyan, K., Acosta-Pulido, J. A., Lazaro, C., Marti-Nez-Lombilla, C., Grinon-Marin, A. B., Yabar, A. Pastor, Protasio, C., Carnerero, M. I., Jermak, H., Steele, I. A., Larionov, V. M., Borman, G. A., Grishina, T. S., MAGIC Collaboration, and Fermi-LAT Collaboration
Subjects: Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, gamma rays: galaxies, Astrophysics::Cosmology and Extragalactic Astrophysics, quasars: individual: PKS 1510-089, galaxies: jets
Abstract: Context. PKS 1510 089 is one of only a few flat spectrum radio quasars detected in the very-high-energy (VHE, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510 089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510 089 with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes during a long, high gamma-ray state in May 2015. In order to perform broadband modeling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray, and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510 089 was detected by MAGIC during a few day-long observations performed in the middle of a long, high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. However, owing to large uncertainty on the knot separation time, the association with the VHE gamma-ray emission cannot be firmly established. The spectral shape in the VHE band during the flare is similar to those obtained during previous measurements of the source. The observed flux variability sets constraints for the first time on the size of the region from which VHE gamma rays are emitted. We model the broadband SED in the framework of the external Compton scenario and discuss the possible emission site in view of multiwavelength data and alternative emission models.

13. Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

Author: Carnerero M., Raiteri C., Villata M., Acosta-Pulido J., Larionov V., Smith P., D'Ammando F., Agudo I., Arévalo M., Bachev R., Barnes J., Boeva S., Bozhilov V., Carosati D., Casadio C., Chen W., Damljanovic G., Eswaraiah E., Forné E., Gantchev G., Gómez J., González-Morales P., Griñón-Marín A., Grishina T., Holden M., Ibryamov S., Joner M., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Koptelova E., Kurtanidze O., Kurtanidze S., Larionova E., Larionova L., Latev G., Lázaro C., Ligustri R., Lin H., Marscher A., Martínez-Lombilla C., McBreen B., Mihov B., Molina S., Moody J., Morozova D., Nikolashvili M., Nilsson K., Ovcharov E., Pace C., Panwar N., Pastor Yabar A., Pearson R., Pinna F., Protasio C., Rizzi N., Redondo-Lorenzo F., Rodríguez-Coira G., Ros J., Sadun A., Savchenko S., Semkov E., Slavcheva-Mihova L., Smith N., Strigachev A., Troitskaya Y., Troitsky I., Vasilyev A., Vince O., Carnerero M., Raiteri C., Villata M., Acosta-Pulido J., Larionov V., Smith P., D'Ammando F., Agudo I., Arévalo M., Bachev R., Barnes J., Boeva S., Bozhilov V., Carosati D., Casadio C., Chen W., Damljanovic G., Eswaraiah E., Forné E., Gantchev G., Gómez J., González-Morales P., Griñón-Marín A., Grishina T., Holden M., Ibryamov S., Joner M., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Koptelova E., Kurtanidze O., Kurtanidze S., Larionova E., Larionova L., Latev G., Lázaro C., Ligustri R., Lin H., Marscher A., Martínez-Lombilla C., McBreen B., Mihov B., Molina S., Moody J., Morozova D., Nikolashvili M., Nilsson K., Ovcharov E., Pace C., Panwar N., Pastor Yabar A., Pearson R., Pinna F., Protasio C., Rizzi N., Redondo-Lorenzo F., Rodríguez-Coira G., Ros J., Sadun A., Savchenko S., Semkov E., Slavcheva-Mihova L., Smith N., Strigachev A., Troitskaya Y., Troitsky I., Vasilyev A., and Vince O.
Abstract: © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We report on long-term multiwavelength monitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007-2015, characterized by several extreme flares. The ratio between the optical, X-ray and γ-ray fluxes is very variable. The γ-ray flux variations show a fair correlation with the optical ones starting from 2012. We analyse spectropolarimetric data and find wavelength-dependence of the polarization degree (P), which is compatible with the presence of the host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA). Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of the EVPA. We build broad-band spectral energy distributions with simultaneous near-infrared and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite. They show strong variability in both flux and X-ray spectr al shape and suggest a shift of the synchrotron peak up to a factor of ~50 in frequency. The interpretation of the flux and spectral variability is compatible with jet models including at least two emitting regions that can change their orientation with respect to the line of sight.

14. Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

Author: Carnerero M., Raiteri C., Villata M., Acosta-Pulido J., Larionov V., Smith P., D'Ammando F., Agudo I., Arévalo M., Bachev R., Barnes J., Boeva S., Bozhilov V., Carosati D., Casadio C., Chen W., Damljanovic G., Eswaraiah E., Forné E., Gantchev G., Gómez J., González-Morales P., Griñón-Marín A., Grishina T., Holden M., Ibryamov S., Joner M., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Koptelova E., Kurtanidze O., Kurtanidze S., Larionova E., Larionova L., Latev G., Lázaro C., Ligustri R., Lin H., Marscher A., Martínez-Lombilla C., McBreen B., Mihov B., Molina S., Moody J., Morozova D., Nikolashvili M., Nilsson K., Ovcharov E., Pace C., Panwar N., Pastor Yabar A., Pearson R., Pinna F., Protasio C., Rizzi N., Redondo-Lorenzo F., Rodríguez-Coira G., Ros J., Sadun A., Savchenko S., Semkov E., Slavcheva-Mihova L., Smith N., Strigachev A., Troitskaya Y., Troitsky I., Vasilyev A., Vince O., Carnerero M., Raiteri C., Villata M., Acosta-Pulido J., Larionov V., Smith P., D'Ammando F., Agudo I., Arévalo M., Bachev R., Barnes J., Boeva S., Bozhilov V., Carosati D., Casadio C., Chen W., Damljanovic G., Eswaraiah E., Forné E., Gantchev G., Gómez J., González-Morales P., Griñón-Marín A., Grishina T., Holden M., Ibryamov S., Joner M., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Koptelova E., Kurtanidze O., Kurtanidze S., Larionova E., Larionova L., Latev G., Lázaro C., Ligustri R., Lin H., Marscher A., Martínez-Lombilla C., McBreen B., Mihov B., Molina S., Moody J., Morozova D., Nikolashvili M., Nilsson K., Ovcharov E., Pace C., Panwar N., Pastor Yabar A., Pearson R., Pinna F., Protasio C., Rizzi N., Redondo-Lorenzo F., Rodríguez-Coira G., Ros J., Sadun A., Savchenko S., Semkov E., Slavcheva-Mihova L., Smith N., Strigachev A., Troitskaya Y., Troitsky I., Vasilyev A., and Vince O.
Abstract: © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We report on long-term multiwavelength monitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007-2015, characterized by several extreme flares. The ratio between the optical, X-ray and γ-ray fluxes is very variable. The γ-ray flux variations show a fair correlation with the optical ones starting from 2012. We analyse spectropolarimetric data and find wavelength-dependence of the polarization degree (P), which is compatible with the presence of the host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA). Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of the EVPA. We build broad-band spectral energy distributions with simultaneous near-infrared and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite. They show strong variability in both flux and X-ray spectr al shape and suggest a shift of the synchrotron peak up to a factor of ~50 in frequency. The interpretation of the flux and spectral variability is compatible with jet models including at least two emitting regions that can change their orientation with respect to the line of sight.

15. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

Author: Raiteri C., Nicastro F., Stamerra A., Villata M., Larionov V., Blinov D., Acosta-Pulido J., Arévalo M., Arkharov A., Bachev R., Borman G., Carnerero M., Carosati D., Cecconi M., Chen W., Damljanovic G., Di Paola A., Ehgamberdiev S., Frasca A., Giroletti M., González-Morales P., Griñon-Marín A., Grishina T., Huang P., Ibryamov S., Klimanov S., Kopatskaya E., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionova E., Larionova L., Lázaro C., Leto G., Liodakis I., Martínez-Lombilla C., Mihov B., Mirzaqulov D., Mokrushina A., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Panopoulou G., Pastor Yabar A., Pinna F., Protasio C., Rizzi N., Sadun A., Savchenko S., Semkov E., Sigua L., Slavcheva-Mihova L., Strigachev A., Tornikoski M., Troitskaya Y., Troitsky I., Vasilyev A., Vera R., Vince O., Zanmar Sanchez R., Raiteri C., Nicastro F., Stamerra A., Villata M., Larionov V., Blinov D., Acosta-Pulido J., Arévalo M., Arkharov A., Bachev R., Borman G., Carnerero M., Carosati D., Cecconi M., Chen W., Damljanovic G., Di Paola A., Ehgamberdiev S., Frasca A., Giroletti M., González-Morales P., Griñon-Marín A., Grishina T., Huang P., Ibryamov S., Klimanov S., Kopatskaya E., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionova E., Larionova L., Lázaro C., Leto G., Liodakis I., Martínez-Lombilla C., Mihov B., Mirzaqulov D., Mokrushina A., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Panopoulou G., Pastor Yabar A., Pinna F., Protasio C., Rizzi N., Sadun A., Savchenko S., Semkov E., Sigua L., Slavcheva-Mihova L., Strigachev A., Tornikoski M., Troitskaya Y., Troitsky I., Vasilyev A., Vera R., Vince O., and Zanmar Sanchez R.
Abstract: © 2016 The Authors.In 2015 July 29-September 1, the satellite XMM-Newton pointed at the BL Lac object PG 1553+133 six times, collecting data for 218 h. During one of these epochs, simultaneous observations by the Swift satellite were requested to compare the results of the X-ray and optical-UV instruments. Optical, near-infrared and radio monitoring was carried out by the Whole Earth Blazar Telescope (WEBT) collaboration for the whole observing season. We here present the results of the analysis of all these data, together with an investigation of the source photometric and polarimetric behaviour over the last 3 yr. The 2015 EPIC spectra show slight curvature and the corresponding light curves display fast X-ray variability with a time-scale of the order of 1 h. In contrast to previous results, during the brightest X-ray states detected in 2015 the simple log-parabolic model that best fits the XMM-Newton data also reproduces reasonably well the whole synchrotron bump, suggesting a peak in the near- UV band. We found evidence of a wide rotation of the polarization angle in 2014, when the polarization degree was variable, but the flux remained almost constant. This is difficult to interpret with deterministic jet emission models, while it can be easily reproduced by assuming some turbulence of the magnetic field.

16. Blazar spectral variability as explained by a twisted inhomogeneous jet

Author: Raiteri C., Villata M., Acosta-Pulido J., Agudo I., Arkharov A., Bachev R., Baida G., Benítez E., Borman G., Boschin W., Bozhilov V., Butuzova M., Calcidese P., Carnerero M., Carosati D., Casadio C., Castro-Segura N., Chen W., Damljanovic G., D'Ammando F., Di Paola A., Echevarría J., Efimova N., Ehgamberdiev S., Espinosa C., Fuentes A., Giunta A., Gómez J., Grishina T., Gurwell M., Hiriart D., Jermak H., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Kuratov K., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionov V., Larionova E., Larionova L., Lázaro C., Lin C., Malmrose M., Marscher A., Matsumoto K., McBreen B., Michel R., Mihov B., Minev M., Mirzaqulov D., Mokrushina A., Molina S., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Okhmat D., Ovcharov E., Pinna F., Polakis T., Protasio C., Pursimo T., Redondo-Lorenzo F., Rizzi N., Rodriguez-Coira G., Sadakane K., Sadun A., Samal M., Savchenko S., Semkov E., Skiff B., Slavcheva-Mihova L., Smith P., Steele I., Raiteri C., Villata M., Acosta-Pulido J., Agudo I., Arkharov A., Bachev R., Baida G., Benítez E., Borman G., Boschin W., Bozhilov V., Butuzova M., Calcidese P., Carnerero M., Carosati D., Casadio C., Castro-Segura N., Chen W., Damljanovic G., D'Ammando F., Di Paola A., Echevarría J., Efimova N., Ehgamberdiev S., Espinosa C., Fuentes A., Giunta A., Gómez J., Grishina T., Gurwell M., Hiriart D., Jermak H., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Kuratov K., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionov V., Larionova E., Larionova L., Lázaro C., Lin C., Malmrose M., Marscher A., Matsumoto K., McBreen B., Michel R., Mihov B., Minev M., Mirzaqulov D., Mokrushina A., Molina S., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Okhmat D., Ovcharov E., Pinna F., Polakis T., Protasio C., Pursimo T., Redondo-Lorenzo F., Rizzi N., Rodriguez-Coira G., Sadakane K., Sadun A., Samal M., Savchenko S., Semkov E., Skiff B., Slavcheva-Mihova L., Smith P., and Steele I.
Abstract: © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions - such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution - can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six ma

17. Blazar spectral variability as explained by a twisted inhomogeneous jet

Author: Raiteri C., Villata M., Acosta-Pulido J., Agudo I., Arkharov A., Bachev R., Baida G., Benítez E., Borman G., Boschin W., Bozhilov V., Butuzova M., Calcidese P., Carnerero M., Carosati D., Casadio C., Castro-Segura N., Chen W., Damljanovic G., D'Ammando F., Di Paola A., Echevarría J., Efimova N., Ehgamberdiev S., Espinosa C., Fuentes A., Giunta A., Gómez J., Grishina T., Gurwell M., Hiriart D., Jermak H., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Kuratov K., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionov V., Larionova E., Larionova L., Lázaro C., Lin C., Malmrose M., Marscher A., Matsumoto K., McBreen B., Michel R., Mihov B., Minev M., Mirzaqulov D., Mokrushina A., Molina S., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Okhmat D., Ovcharov E., Pinna F., Polakis T., Protasio C., Pursimo T., Redondo-Lorenzo F., Rizzi N., Rodriguez-Coira G., Sadakane K., Sadun A., Samal M., Savchenko S., Semkov E., Skiff B., Slavcheva-Mihova L., Smith P., Steele I., Raiteri C., Villata M., Acosta-Pulido J., Agudo I., Arkharov A., Bachev R., Baida G., Benítez E., Borman G., Boschin W., Bozhilov V., Butuzova M., Calcidese P., Carnerero M., Carosati D., Casadio C., Castro-Segura N., Chen W., Damljanovic G., D'Ammando F., Di Paola A., Echevarría J., Efimova N., Ehgamberdiev S., Espinosa C., Fuentes A., Giunta A., Gómez J., Grishina T., Gurwell M., Hiriart D., Jermak H., Jordan B., Jorstad S., Joshi M., Kopatskaya E., Kuratov K., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionov V., Larionova E., Larionova L., Lázaro C., Lin C., Malmrose M., Marscher A., Matsumoto K., McBreen B., Michel R., Mihov B., Minev M., Mirzaqulov D., Mokrushina A., Molina S., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Okhmat D., Ovcharov E., Pinna F., Polakis T., Protasio C., Pursimo T., Redondo-Lorenzo F., Rizzi N., Rodriguez-Coira G., Sadakane K., Sadun A., Samal M., Savchenko S., Semkov E., Skiff B., Slavcheva-Mihova L., Smith P., and Steele I.
Abstract: © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions - such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution - can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six ma

18. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

Author: Raiteri C., Nicastro F., Stamerra A., Villata M., Larionov V., Blinov D., Acosta-Pulido J., Arévalo M., Arkharov A., Bachev R., Borman G., Carnerero M., Carosati D., Cecconi M., Chen W., Damljanovic G., Di Paola A., Ehgamberdiev S., Frasca A., Giroletti M., González-Morales P., Griñon-Marín A., Grishina T., Huang P., Ibryamov S., Klimanov S., Kopatskaya E., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionova E., Larionova L., Lázaro C., Leto G., Liodakis I., Martínez-Lombilla C., Mihov B., Mirzaqulov D., Mokrushina A., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Panopoulou G., Pastor Yabar A., Pinna F., Protasio C., Rizzi N., Sadun A., Savchenko S., Semkov E., Sigua L., Slavcheva-Mihova L., Strigachev A., Tornikoski M., Troitskaya Y., Troitsky I., Vasilyev A., Vera R., Vince O., Zanmar Sanchez R., Raiteri C., Nicastro F., Stamerra A., Villata M., Larionov V., Blinov D., Acosta-Pulido J., Arévalo M., Arkharov A., Bachev R., Borman G., Carnerero M., Carosati D., Cecconi M., Chen W., Damljanovic G., Di Paola A., Ehgamberdiev S., Frasca A., Giroletti M., González-Morales P., Griñon-Marín A., Grishina T., Huang P., Ibryamov S., Klimanov S., Kopatskaya E., Kurtanidze O., Kurtanidze S., Lähteenmäki A., Larionova E., Larionova L., Lázaro C., Leto G., Liodakis I., Martínez-Lombilla C., Mihov B., Mirzaqulov D., Mokrushina A., Moody J., Morozova D., Nazarov S., Nikolashvili M., Ohlert J., Panopoulou G., Pastor Yabar A., Pinna F., Protasio C., Rizzi N., Sadun A., Savchenko S., Semkov E., Sigua L., Slavcheva-Mihova L., Strigachev A., Tornikoski M., Troitskaya Y., Troitsky I., Vasilyev A., Vera R., Vince O., and Zanmar Sanchez R.
Abstract: © 2016 The Authors.In 2015 July 29-September 1, the satellite XMM-Newton pointed at the BL Lac object PG 1553+133 six times, collecting data for 218 h. During one of these epochs, simultaneous observations by the Swift satellite were requested to compare the results of the X-ray and optical-UV instruments. Optical, near-infrared and radio monitoring was carried out by the Whole Earth Blazar Telescope (WEBT) collaboration for the whole observing season. We here present the results of the analysis of all these data, together with an investigation of the source photometric and polarimetric behaviour over the last 3 yr. The 2015 EPIC spectra show slight curvature and the corresponding light curves display fast X-ray variability with a time-scale of the order of 1 h. In contrast to previous results, during the brightest X-ray states detected in 2015 the simple log-parabolic model that best fits the XMM-Newton data also reproduces reasonably well the whole synchrotron bump, suggesting a peak in the near- UV band. We found evidence of a wide rotation of the polarization angle in 2014, when the polarization degree was variable, but the flux remained almost constant. This is difficult to interpret with deterministic jet emission models, while it can be easily reproduced by assuming some turbulence of the magnetic field.

19. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Author: M. Hayashida, Satoshi Masuda, Arka Chatterjee, Juan Abel Barrio, D. Fidalgo, Yu. V. Troitskaya, Svetlana G. Jorstad, Emilia Järvelä, Marc Ribó, J. A. Acosta Pulido, Wrijupan Bhattacharyya, L. Maraschi, Kari Nilsson, P. Bangale, Hidetoshi Kubo, J. Hose, Stefano Ansoldi, Yusuke Konno, D. Elsaesser, Riccardo Paoletti, Tomislav Terzić, Francesco Longo, Elina Lindfors, P. G. Prada Moroni, Daniel Mazin, G. A. Borman, Alessandro Carosi, V. Fallah Ramazani, J. Palacio, D. Ninci, Kazuma Ishio, Pratik Majumdar, A. Berti, J. M. Paredes, Antonio Stamerra, N. Torres-Albà, J. Kushida, M. V. Fonseca, Jose Luis Contreras, M. Peresano, M. Makariev, G. Bonnoli, D. Kuveždić, Tarek M. Hassan, W. Bednarek, G. Pedaletti, Juan Cortina, Fabrizio Tavecchio, Martin Will, Chiara Righi, R. Ch. Berse, Ll. Font, Razmik Mirzoyan, Rodolfo Carosi, Dario Hrupec, Jose Miguel Miranda, J. Becerra González, M. A. Lopez, J. R. Garcia, Marina Manganaro, U. Barres de Almeida, P. Temnikov, E. Colombo, Oscar Blanch, T. S. Grishina, Mitsunari Takahashi, Stefano Covino, Louis Antonelli, Damir Lelas, Valeri M. Larionov, Aaron Dominguez, D. Galindo, Merja Tornikoski, Sergey S. Savchenko, Francesco Dazzi, Manuel Delfino, D. Dominis Prester, Wolfgang Rhode, Nikola Godinovic, Shimpei Tsujimoto, Tomoki Saito, Giovanni Ceribella, A. A. Vasilyev, Ana Babić, P. Cumani, L. O. Takalo, Konstancja Satalecka, L. Nogués, Michele Doro, Max Ludwig Ahnen, Dorota Sobczyńska, R. Ojha, K. Mielke, J. Finke, E. Moretti, Ievgen Vovk, P. Giammaria, Jordi Delgado, F. Di Pierro, Camilla Maggio, Daniela Dorner, Dariusz Gora, M. Gaug, G. Vanzo, C. Protasio, J. Herrera, D. Hadasch, Alba Fernández-Barral, Carolina Casadio, Anne Lähteenmäki, Mosè Mariotti, Masahiro Teshima, Alexander Hahn, E. Prandini, Cosimo Nigro, M. Nievas Rosillo, T. Nagayoshi, Kyoshi Nishijima, M. Minev, Iva Šnidarić, T. Schweizer, J. E. Ward, Sidika Merve Colak, E. N. Kopatskaya, A. Niedzwiecki, Koji Noda, Elisa Bernardini, Ivan S. Troitsky, David Paneque, D. Guberman, Saverio Lombardi, Andrea Rugliancich, V. Ramakrishnan, M. I. Martínez, Sabrina Einecke, Ivica Puljak, Pierre Colin, Markus Garczarczyk, M. I. Carnerero, Talvikki Hovatta, Sol N. Molina, P. Da Vela, Julian Sitarek, S. Paiano, Karl Mannheim, D. A. Morozova, A. De Angelis, A. Treves, Vitaly Neustroev, M. Vazquez Acosta, L. V. Larionova, G. Maneva, I. Agudo, Adrian Biland, Tihomir Surić, J. Rico, Dominik Baack, Alan P. Marscher, Christian Fruck, Victoria Moreno, Darko Zarić, B. De Lotto, Abelardo Moralejo, I. Reichardt, Mark Gurwell, B. Banerjee, Marcel Strzys, C. Arcaro, R. J. García López, Massimo Persic, Yasuyuki T. Tanaka, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Baack, D., Babić, A., Banerjee, B., Bangale, P., Barres De Almeida, U., Barrio, J. A., Bednarek, W., Bernardini, E., Berse, R. Ch., Berti, A., Bhattacharyya, W., Biland, A., Blanch, O., Bonnoli, G., Carosi, R., Carosi, A., Ceribella, G., 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., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fallah Ramazani, V., Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., García López, R. J., 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., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Mielke, K., Minev, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moreno, V., Moretti, E., Nagayoshi, T., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., 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., Persic, M., Prada Moroni, P. G., Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takahashi, M., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Treves, A., Tsujimoto, S., Vanzo, G., Vazquez Acosta, M., Vovk, I., Ward, J. E., Will, M., Zarić, D., Becerra González, J., Tanaka, Y., Ojha, R., Finke, J., Lähteenmäki, A., Järvelä, E., Tornikoski, M., Ramakrishnan, V., Hovatta, T., Jorstad, S. G., Marscher, A. P., Larionov, V. M., Borman, G. A., Grishina, T. S., Kopatskaya, E. N., Larionova, L. V., Morozova, D. A., Savchenko, S. S., Troitskaya, Yu. V., Troitsky, I. S., Vasilyev, A. A., Agudo, I., Molina, S. N., Casadio, C., Gurwell, M., Carnerero, M. I., Protasio, C., Acosta Pulido, J. A., Ministerio de Economía y Competitividad (España), Swiss National Science Foundation, Federal Ministry of Education and Research (Germany), Junta de Andalucía, Max Planck Society, Universitat de Barcelona, Department of Electronics and Nanoengineering, Aalto-yliopisto, and Aalto University
Subjects: individual: S4 0954+65 [BL Lacertae objects], Active galactic nucleus, active [Galaxies], BL Lacertae objects: individual: S4 0954+65, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Galaxies: active, Gamma rays: galaxies, Astronomy and Astrophysics, Space and Planetary Science, 0103 physical sciences, Gamma ray astronomy, Astronomia de raigs gamma, gamma rays:galaxies, galaxies:active, BL Lacertae objects:individual:S40954+65, Blazar, 010303 astronomy & astrophysics, Quasars, Astrophysics::Galaxy Astrophysics, Quàsars, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, gamma rays: galaxies, galaxies: active, galaxie [Gamma rays], 010308 nuclear & particles physics, Compton scattering, Optical polarization, Quasar, Astronomy and Astrophysic, Galaxies, Redshift, Galàxies, galaxies [gamma rays], ddc:520, Spectral energy distribution, Física nuclear, Astrophysics - High Energy Astrophysical Phenomena, Radio wave
Abstract: The very high energy (VHE ¿ 100 GeV) -ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z = 0.368 or z ¿ 0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. Methods. We investigated the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and have put it in context with possible emission scenarios. We collected photometric data in radio, optical, X-ray, and ¿-ray. We studied both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Results. Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy ¿-ray(HE, 100 MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100. Conclusions. The high emission state during the flare allows us to compile the simultaneous broadband SED and to characterize it in the scope of blazar jet emission models. The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars (FSRQs), that is, inverse Compton scattering on an external soft photon field from the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to FSRQs and low-frequency peaked BL Lac objects (LBL). © ESO 2018., 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, CSD2009-00064), and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2012-0234 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, 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. IA acknowledges support by a Ramón y Cajal grant of the Ministerio de Economía, Industria y Competitividad (MINECO) of Spain. The research at the IAA–CSIC was supported in part by the MINECO through grants AYA2016–80889–P, AYA2013–40825–P, and AYA2010–14844, and by the regional government of Andalucía through grant P09–FQM–4784.
Published: 2018

20. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

Author: I. Snidaric, M. Strzys, M. Vazquez Acosta, J. A. Acosta-Pulido, Vishal Bala, B. De Lotto, J. Palacio, Julian Sitarek, L. Nogués, E. Colombo, B. Biasuzzi, M. Makariev, C. Fruck, D. Nakajima, T. Toyama, Diego F. Torres, Abelardo Moralejo, Stefan Larsson, Navpreet Kaur, R. Desiante, L. O. Takalo, I. Reichardt, Francesco Longo, E. Prandini, Arka Chatterjee, A. Sillanpää, M. Peresano, A. Niedzwiecki, D. Hadasch, Elina Lindfors, D. Fidalgo, M. Engelkemeier, C. Protasio, S. Bonnefoy, Iain A. Steele, Daniel Mazin, S. Paiano, Karl Mannheim, Takashi Saito, Nicholas R. MacDonald, David Paneque, D. Guberman, Anne Lähteenmäki, Svetlana G. Jorstad, Kiran S. Baliyan, Tarek M. Hassan, W. Bednarek, L. Perri, Fabrizio Tavecchio, U. Menzel, Masahiro Teshima, M. Palatiello, Marina Manganaro, Stefano Ansoldi, Yusuke Konno, Ll. Font, Merja Tornikoski, S. Schroeder, Ivica Puljak, Riccardo Paoletti, D. Eisenacher Glawion, F. Di Pierro, Pierre Colin, Oscar Blanch, Pratik Majumdar, Mosè Mariotti, Markus Garczarczyk, Francesco Dazzi, M. Nievas Rosillo, T. S. Grishina, Louis Antonelli, M. V. Fonseca, A. Fernández-Barral, J. Hose, Max Ludwig Ahnen, F. Borracci, Emilia Järvelä, R. J. García López, G. Pedaletti, Thomas Bretz, Stefano Covino, P. Cumani, Kazuma Ishio, C. M. Raiteri, Konstancja Satalecka, T. Surić, M. Doert, M. H. Wu, E. de Oña Wilhelmi, D. Elsaesser, Michele Doro, A. B. Grinon-Marin, Dario Hrupec, J. Becerra González, D. Kuveždić, Nikola Godinovic, P. Temnikov, C. Lázaro, Saverio Lombardi, A. Pastor Yabar, Helen Jermak, Rodolfo Carosi, M. A. Lopez, Antonio Stamerra, J. E. Ward, S. N. Shore, Alessio Berti, P. Giammaria, Filippo D'Ammando, Juan Abel Barrio, R. Reinthal, P. Da Vela, D. Tescaro, P. G. Prada Moroni, Razmik Mirzoyan, U. Barres de Almeida, Massimo Persic, Alessandro Carosi, D. Galindo, Aaron Dominguez, L. Maraschi, Damir Lelas, Kari Nilsson, Daniela Dorner, Dariusz Gora, Gaia Vanzo, N. Torres-Albà, E. Moretti, M. Hayashida, Sameer, M. Gaug, Dorota Sobczyńska, J. M. Paredes, X. Paredes-Fortuny, J. Herrera, C. Martínez-Lombilla, D. Zarić, M. Will, Alexander Hahn, Tomislav Terzić, Koji Noda, Marc Ribó, Elisa Bernardini, J. R. Garcia, Gareth Hughes, Hidetoshi Kubo, K. Nishijima, D. Dominis Prester, V. Ramakrishnan, V. Fallah Ramazani, M. I. Martínez, G. A. Borman, Wolfgang Rhode, P. Bangale, J. Kushida, Jose Luis Contreras, Sabrina Einecke, G. Bonnoli, Juan Cortina, B. Banerjee, C. Arcaro, Valeri M. Larionov, Ana Babić, Adrian Biland, J. Rico, M. I. Carnerero, Alan P. Marscher, Ievgen Vovk, A. De Angelis, A. Treves, Vitaly Neustroev, T. Schweizer, G. Maneva, Juri Poutanen, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Babiä , A., Banerjee, B., Bangale, P., Barres De Almeida, U., Barrio, J. A., Bednarek, W., Bernardini, E., Berti, Alessio, Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carosi, R., Carosi, A., Chatterjee, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Cumani, P., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., De OÃ±a Wilhelmi, E., Di Pierro, F., Doert, M., Domãnguez, A., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Eisenacher Glawion, D., Elsaesser, D., Engelkemeier, M., Fallah Ramazani, V., FernÃ¡ndez Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., GarcÃa LÃ³pez, R. J., Garczarczyk, M., Gaug, M., Giammaria, P., Godinoviä , N., Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hassan, T., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Ishio, K., Konno, Y., Kubo, H., Kushida, J., Kuveå¾diä , D., Lelas, D., Lindfors, E., Lombardi, S., Longo, Francesco, Lã³pez, M., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martãnez, M., Mazin, D., Menzel, U., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nilsson, K., Nishijima, K., Noda, K., Noguã©s, L., Paiano, S., Palacio, J., Palatiello, Michele, Paneque, D., Paoletti, R., Paredes, J. M., Paredes Fortuny, X., Pedaletti, G., Peresano, M., Perri, L., Persic, M., Poutanen, J., Prada Moroni, P. G., Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Rhode, W., Ribã³, M., Rico, J., Saito, T., Satalecka, K., Schroeder, S., Schweizer, T., Shore, S. N., Sillanpã¤ã¤, A., Sitarek, J, Å nidariä , I., Sobczynska, D., Stamerra, A., Strzys, M., Suriä , T., Takalo, L., Tavecchio, F., Temnikov, P., Terziä , T., Tescaro, D., Teshima, M., Torres, D. F., Torres AlbÃ , N., Toyama, T., Treves, A., Vanzo, G., Vazquez Acosta, M., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zariä , D., Desiante, R., Becerra GonzÃ¡lez, J., D'Ammando, F., Larsson, S., Raiteri, C. M., Reinthal, R., Lã¤hteenmã¤ki, A., Jã¤rvelã¤, E., Tornikoski, M., Ramakrishnan, V., Jorstad, S. G., Marscher, A. P., Bala, V., Macdonald, N. R., Kaur, N., Sameer, Null, Baliyan, K., Acosta Pulido, J. A., Lazaro, C., MartÃ Nez Lombilla, C., Grinon Marin, A. B., Pastor Yabar, A., Protasio, C., Carnerero, M. I., Jermak, H., Steele, I. A., Larionov, V. M., Borman, G. A., Grishina, T. S., Swiss Federal Institute of Technology Zurich, University of Udine, INAF National Institute for Astrophysics, University of Padova, University of Rijeka, Saha Institute of Nuclear Physics, Max Planck Institute for Physics, Complutense University, University of Łódź, German Electron Synchrotron, Autonomous University of Barcelona, University of Siena, University of Würzburg, Instituto de Astrofísica de Canarias, Institute of Space Studies of Catalonia, Dortmund University, Finnish MAGIC Consortium, University of Barcelona, The University of Tokyo, Osservatorio Astronomicodi Roma, Bulgarian Academy of Sciences, University of Pisa, University of Bologna, KTH Royal Institute of Technology, University of Turku, Metsähovi Radio Observatory, Department of Radio Science and Engineering, Boston University, Physical Research Laboratory India, Lancaster University, Liverpool John Moores University, St. Petersburg State University, Crimean Astrophysical Observatory, Department of Electronics and Nanoengineering, Aalto-yliopisto, and Aalto University
Subjects: galaxies [Gamma rays], VHE [gamma ray], Astrophysics, 01 natural sciences, rotation, jet [Galaxies], law.invention, law, galaxies, active, galaxies: jets, gamma rays: galaxies, quasars: individual: PKS 1510-089, Broadband, QD, 010303 astronomy & astrophysics, QC, QB, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), galaxie [Gamma rays], Gamma ray, Optical polarization, Galaxies: active, Polarization (waves), Gamma rays: galaxies, optical [polarization], Spectral energy distribution, Electrónica, Física nuclear, Electricidad, Astrophysics - High Energy Astrophysical Phenomena, Galaxies: jets, Quasars: individual: PKS 1510-089, Astronomy and Astrophysics, Space and Planetary Science, Flare, active [Galaxies], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Photometry (optics), X-ray, 0103 physical sciences, individual: PKS 1510-089 [Quasars], quasar, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, Quasar, Astronomy and Astrophysic, MAGIC, flux, ddc:520, spectral, jets [Galaxies]
Abstract: Context. PKS 1510-089 is one of only a few flat spectrum radio quasars detected in the VHE (very-high-energy, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510-089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510-089 with the MAGIC telescopes during a long high gamma-ray state in May 2015. In order to perform broadband modelling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510-089 has been detected by MAGIC during a few day-long observations performed in the middle of a long, high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. However, due to large uncertainty on the knot separation time, the association with the VHE gamma-ray emission cannot be firmly established. The spectral shape in the VHE band during the flare is similar to the ones obtained during previous measurements of the source. The observed flux variability sets for the first time constraints on the size of the region from which VHE gamma rays are emitted. We model the broadband SED in the framework of the external Compton scenario and discuss the possible emission site in view of multiwavelength data and alternative emission models., 12 pages, 10 figures, accepted for a publication in A&A

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20 results on '"Protasio, C."'

1. Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017

2. The detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

3. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

4. Blazar spectral variability as explained by a twisted inhomogeneous jet

5. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

6. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

7. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

8. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510−089 in 2015

9. Blazar spectral variability as explained by a twisted inhomogeneous jet

10. Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

11. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

12. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

13. Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

14. Dissecting the long-term emission behaviour of the BL Lac object Mrk 421

15. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

16. Blazar spectral variability as explained by a twisted inhomogeneous jet

17. Blazar spectral variability as explained by a twisted inhomogeneous jet

18. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

19. Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

20. Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

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20 results on '"Protasio, C."'

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