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29,494 results on '"Rodriguez J"'

201. Energy calibration of the NEXT-White detector with 1% resolution near Q$_{\beta\beta}$ of $^{136}$Xe

Author

Renner, J., López, G. Díaz, Ferrario, P., Morata, J. A. Hernando, Kekic, M., Martínez-Lema, G., Monrabal, F., Gómez-Cadenas, J. J., Adams, C., Álvarez, V., Arazi, L., Arnquist, I. J., Azevedo, C. D. R, Bailey, K., Ballester, F., Benlloch-Rodríguez, J. M., Borges, F. I. G. M., Byrnes, N., Cárcel, S., Carrión, J. V., Cebrián, S., Church, E., Conde, C. A. N., Contreras, T., Díaz, J., Diesburg, M., Escada, J., Esteve, R., Felkai, R., Fernandes, A. F. M., Fernandes, L. M. P., Ferreira, A. L., Freitas, E. D. C., Generowicz, J., Ghosh, S., Goldschmidt, A., González-Díaz, D., Guenette, R., Gutiérrez, R. M., Haefner, J., Hafidi, K., Hauptman, J., Henriques, C. A. O., Herrero, P., Herrero, V., Ifergan, Y., Johnston, S., Jones, B. J. P., Labarga, L., Laing, A., Lebrun, P., López-March, N., Losada, M., Mano, R. D. P., Martín-Albo, J., Martínez, A., McDonald, A. D., Monteiro, C. M. B., Mora, F. J., Vidal, J. Muñoz, Novella, P., Nygren, D. R., Palmeiro, B., Para, A., Pérez, J., Psihas, F., Querol, M., Repond, J., Riordan, S., Ripoll, L., García, Y. Rodríguez, Rodríguez, J., Rogers, L., Romeo, B., Romo-Luque, C., Santos, F. P., Santos, J. M. F. dos, Simón, A., Sofka, C., Sorel, M., Stiegler, T., Toledo, J. F., Torrent, J., Usón, A., Veloso, J. F. C. A., Webb, R., Weiss-Babai, R., White, J. T., Woodruff, K., and Yahlali, N.

Subjects
Physics - Instrumentation and Detectors
Abstract

Excellent energy resolution is one of the primary advantages of electroluminescent high pressure xenon TPCs, and searches for rare physics events such as neutrinoless double-beta decay ($\beta\beta0\nu$) require precise energy measurements. Using the NEXT-White detector, developed by the NEXT (Neutrino Experiment with a Xenon TPC) collaboration, we show for the first time that an energy resolution of 1% FWHM can be achieved at 2.6 MeV, establishing the present technology as the one with the best energy resolution of all xenon detectors for $\beta\beta0\nu$ searches., Comment: 13 pages, 7 figures; accepted to JHEP

Published
2019
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202. Demonstration of the event identification capabilities of the NEXT-White detector

Author

NEXT Collaboration, Ferrario, P., Benlloch-Rodríguez, J. M., López, G. Díaz, Morata, J. A. Hernando, Kekic, M., Renner, J., Usón, A., Gómez-Cadenas, J. J., Adams, C., Álvarez, V., Arazi, L., Arnquist, I. J., Azevedo, C. D. R, Bailey, K., Ballester, F., Borges, F. I. G. M., Byrnes, N., Cárcel, S., Carrión, J. V., Cebrián, S., Church, E., Conde, C. A. N., Contreras, T., Díaz, J., Diesburg, M., Escada, J., Esteve, R., Felkai, R., Fernandes, A. F. M., Fernandes, L. M. P., Ferreira, A. L., Freitas, E. D. C., Generowicz, J., Ghosh, S., Goldschmidt, A., González-Díaz, D., Guenette, R., Gutiérrez, R. M., Haefner, J., Hafidi, K., Hauptman, J., Henriques, C. A. O., Herrero, P., Herrero, V., Ifergan, Y., Johnston, S., Jones, B. J. P., Labarga, L., Laing, A., Lebrun, P., López-March, N., Losada, M., Mano, R. D. P., Martín-Albo, J., Martínez, A., Martínez-Lema, G., McDonald, A. D., Monrabal, F., Monteiro, C. M. B., Mora, F. J., Vidal, J. Muñoz, Novella, P., Nygren, D. R., Palmeiro, B., Para, A., Pérez, J., Psihas, F., Querol, M., Repond, J., Riordan, S., Ripoll, L., García, Y. Rodríguez, Rodríguez, J., Rogers, L., Romeo, B., Romo-Luque, C., Santos, F. P., Santos, J. M. F. dos, Simón, A., Sofka, C., Sorel, M., Stiegler, T., Toledo, J. F., Torrent, J., Veloso, J. F. C. A., Webb, R., Weiss-Babai, R., White, J. T., Woodruff, K., and Yahlali, N.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

In experiments searching for neutrinoless double-beta decay, the possibility of identifying the two emitted electrons is a powerful tool in rejecting background events and therefore improving the overall sensitivity of the experiment. In this paper we present the first measurement of the efficiency of a cut based on the different event signatures of double and single electron tracks, using the data of the NEXT-White detector, the first detector of the NEXT experiment operating underground. Using a \TO\ calibration source to produce signal-like and background-like events with energies near 1.6 MeV, a signal efficiency of $71.6 \pm 1.5_{\textrm{ stat}} \pm 0.3_{\textrm{ sys}} \%$ for a background acceptance of $20.6 \pm 0.4_{\textrm{ stat}} \pm 0.3_{\textrm{ sys}} \%$ is found, in good agreement with Monte Carlo simulations. An extrapolation to the energy region of the neutrinoless double beta decay by means of Monte Carlo simulations is also carried out, and the results obtained show an improvement in background rejection over those obtained at lower energies., Comment: Accepted by JHEP

Published
2019
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203. Measurement of the fluctuations in the number of muons in extensive air showers with the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Cancio, A., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Dembinski, H., Dhital, N., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Halliday, R., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Mezek, G. Kukec, Lago, B. L., LaHurd, D., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lorek, R., Luce, Q., Lucero, A., Lundquist, J. P., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Elipe, G. Torralba, Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valiño, I., Valore, L., Varela, E., C., V. Varma K., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., and Zepeda, A.

Subjects
High Energy Physics - Experiment
Abstract

We present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultrahigh energy cosmic rays. We find that the measured fluctuations are in good agreement with predictions from air shower simulations. This observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultrahigh energies. Our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop., Comment: Published version, 11 pages, 3 figures, 1 table, Supplemental material appended

Published
2021
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204. Potential origin of the state-dependent high-energy tail in the black hole microquasar Cygnus X-1 as seen with INTEGRAL

Author

Cangemi, F., Beuchert, T., Siegert, T., Rodriguez, J., Grinberg, V., Belmont, R., Gouiffès, C., Kreykenbohm, I., Laurent, P., Pottschmidt, K., and Wilms, J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

0.1-10 MeV observations of the black hole microquasar Cygnus X-1 have shown the presence of a spectral feature in the form of a power law in addition to the standard black body and Comptonization components observed by INTEGRAL. This so-called "high-energy tail" has recently been shown to be strong in its hard spectral state and interpreted as high-energy part of the emission from a compact jet. This result was, however, obtained from a data set dominated by hard state observations. In the soft state, only upper limits on the presence and hence the potential parameters of a high-energy tail could be derived. Using an extended data set we aim at obtaining better constraints on the properties of this spectral component in both states. We make use of data obtained from 15 years of observations with the INTEGRAL satellite. The data set is separated into the different states and we analyse stacked state-resolved spectra obtained from the X-ray monitors, the gamma-ray imager, and the gamma-ray spectrometer onboard. A high-energy component is detected in both states confirming its earlier detection in the hard state and its suspected presence in the soft state with INTEGRAL. We first characterize the high-energy tail components in the two states through a model-independent, phenomenological analysis. We then apply physical models based on hybrid Comptonization. The spectra are well modeled in all cases, with a similar goodness of the fits. While in the phenomenological approach the high-enery tail has similar indices in both states, the fits with the physical models seem to indicate different properties. We discuss the potential origins of the high-energy components in both states, and favor an interpretation where the part of the high-energy component is due to a compact jet in the hard state and hybrid Comptonization in either a magnetised or non-magnetised corona in the soft state., Comment: 14 pages, 8 figures. Accepted for a publication in A&A

Published
2021
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205. New upper bounds for the forgotten index among bicyclic graphs

Author

Jahanbani, A., Shahbazi, L., Sheikholeslami, S. M., Rasi, R., and Rodriguez, J.

Subjects
Mathematics - Combinatorics, Computer Science - Discrete Mathematics
Abstract

The forgotten topological index of a graph $G$, denoted by $F(G)$, is defined as the sum of weights $d(u)^{2}+d(v)^{2}$ over all edges $uv$ of $G$ , where $d(u)$ denotes the degree of a vertex $u$. In this paper, we give sharp upper bounds of the F-index (forgotten topological index) over bicyclic graphs, in terms of the order and maximum degree.

Published
2021

206. Design and Performance Analysis of a Highly Efficient Polychromatic Full-Stokes Polarization Modulator for the CRISP Imaging Spectrometer

Author

de Wijn, A. G., Rodríguez, J. de la Cruz, Scharmer, G. B., Sliepen, G., and Sütterlin, P.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

We present the design and performance of a polychromatic polarization modulator for the CRisp Imaging SpectroPolarimeter (CRISP) Fabry-Perot tunable narrow-band imaging spectropolarimer at the Swedish 1-m Solar Telescope (SST). We discuss the design process in depth, compare two possible modulator designs through a tolerance analysis, and investigate thermal sensitivity of the selected design. The trade-offs and procedures described in this paper are generally applicable in the development of broadband polarization modulators. The modulator was built and has been operational since 2015. Its measured performance is close to optimal between 500 and 900~nm, and differences between the design and as-built modulator are largely understood. We show some example data, and briefly review scientific work that used data from SST/CRISP and this modulator.

Published
2021
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207. Characterization and on-field performance of the MuTe Silicon Photomultipliers

Author

Sánchez-Villafrades, J., Peña-Rodríguez, J., Asorey, H., and Núñez, L. A.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The Muon Telescope is a muography experiment for imaging volcanoes in Colombia. It consists of a scintillator tracking system and a water Cherenkov detector used for particle deposited energy measurement. The MuTe operates autonomously in high altitude environments where the temperature gradient reaches up to $10$$^{\circ}$C. In this work, we characterize the breakdown voltage, gain, and noise of the telescope silicon photomultipliers for temperature variations spanning $0$ to $40$$^{\circ}$C. We demonstrated that the discrimination threshold for the MuTe hodoscope must be above 5 pe to avoid contamination due to the SiPM dark count, crosstalk, and afterpulsing. We also assess the MuTe counting rate depending on day-night temperature variations.

Published
2021

208. The FRAM robotic telescope for atmospheric monitoring at the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Velázquez, J. C. Arteaga, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Orchera, P. G. Brichetto, Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Santos, D. Correia dos, Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Palma, F., de Souza, V., De Vito, E., del Río, M., Deligny, O., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, J. M., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Hamal, P., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Janecek, P., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Kunka, N., Lago, B. L., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lu, L., Luce, Q., Lucero, A., Lundquist, J. P., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nasr-Esfahani, A., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Martins, E. E. Pereira, Armand, J. Perez, Bertolli, C. Pérez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Segreto, A., Sehgal, S., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Taricco, C., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valore, L., Varela, E., C., V. Varma K., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watanabe, C., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., Cunniffe, R., Eliášek, J., Ebrová, I., Jelínek, M., Karpov, S., Kubánek, P., and Mašek, M.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

FRAM (F/Photometric Robotic Atmospheric Monitor) is a robotic telescope operated at the Pierre Auger Observatory in Argentina for the purposes of atmospheric monitoring using stellar photometry. As a passive system which does not produce any light that could interfere with the observations of the fluorescence telescopes of the observatory, it complements the active monitoring systems that use lasers. We discuss the applications of stellar photometry for atmospheric monitoring at optical observatories in general and the particular modes of operation employed by the Auger FRAM. We describe in detail the technical aspects of FRAM, the hardware and software requirements for a successful operation of a robotic telescope for such a purpose and their implementation within the FRAM system., Comment: Published version, 27 pages, 8 figures

Published
2021
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209. Design and implementation of the AMIGA embedded system for data acquisition

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Velázquez, J. C. Arteaga, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Binet, V., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Orchera, P. G. Brichetto, Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Santos, D. Correia dos, Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Palma, F., de Souza, V., De Vito, E., del Río, M., Deligny, O., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, J. M., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Hamal, P., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Janecek, P., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Kunka, N., Lago, B. L., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lu, L., Luce, Q., Lundquist, J. P., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nasr-Esfahani, A., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Martins, E. E. Pereira, Armand, J. Perez, Bertolli, C. Pérez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Segreto, A., Sehgal, S., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Tapia, A., Taricco, C., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valore, L., Varela, E., C., V. Varma K., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watanabe, C., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., del Castillo, N., de Innocenti, G., Ferreyro, L., Garavano, S., Gorbeña, D., Leal, N., Ríos, G., Paramidani, M., Pierri, G., Reyes, C., Riello, A., Salum, J. M., Croce, A. P. J. Sedoski, Silva, D., and Varela, C.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The Auger Muon Infill Ground Array (AMIGA) is part of the AugerPrime upgrade of the Pierre Auger Observatory. It consists of particle counters buried 2.3 m underground next to the water-Cherenkov stations that form the 23.5 km$^2$ large infilled array. The reduced distance between detectors in this denser area allows the lowering of the energy threshold for primary cosmic ray reconstruction down to about 10$^{17}$ eV. At the depth of 2.3 m the electromagnetic component of cosmic ray showers is almost entirely absorbed so that the buried scintillators provide an independent and direct measurement of the air showers muon content. This work describes the design and implementation of the AMIGA embedded system, which provides centralized control, data acquisition and environment monitoring to its detectors. The presented system was firstly tested in the engineering array phase ended in 2017, and lately selected as the final design to be installed in all new detectors of the production phase. The system was proven to be robust and reliable and has worked in a stable manner since its first deployment., Comment: Accepted for publication at JINST. Published version, 34 pages, 15 figures, 4 tables

Published
2021
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210. PETALO read-out: A novel approach for data acquisition systems in PET applications

Author

Herrero-Bosch, V., Gadea, R., Aliaga, R. J., Rodríguez, J., Toledo, J. F., Torres-Curado, R., Ballester, F., Esteve, R., Gómez-Cadenas, J. J., and Ferrario, P.

Subjects
Physics - Instrumentation and Detectors
Abstract

PETALO (a Positron Emission Tof Apparatus based on Liquid xenOn) is a new approach for Positron Emission Tomography scanners, based on liquid xenon. The PETALO detector aims at capturing the light produced by the scintillation in LXe taking advantage of its uniform response and continuity. This strategy will lead to a geometrical distortion free behavior compared to other PET detectors. To this end, the sensors chosen for the light readout are SiPMs, which provide large area, high gain and very low noise. In order to take advantage of the unique PETALO detector characteristics a read-out architecture must be designed to meet the following specifications: Electronics associated to detector (front-end and read-out itself) must be fully expandable in terms of detector size. Read-out scheme must be compatible with the non-segmented structure of the detector. Time of Flight (TOF) capabilities must be assured at the scanner level, that is to say front-end and read-out electronics should not degrade LXe time performance. In these proceedings, a new readout concept is introduced which is compatible with a fully continuous medium detector such as PETALO. Results show that the system is feasible, with the introduction of a fast compression technique to further reduce the data bandwidth requirements.

Published
2021
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211. Asymptotic analysis of a thin fluid layer flow between two moving surfaces

Author

Rodríguez, J. M. and Taboada-Vázquez, R.

Subjects
Mathematics - Analysis of PDEs, 35Q35 (Primary) 76M45, 35C20, 41A60, 76D08 (Secondary)
Abstract

In this paper we study the behavior of an incompressible viscous fluid moving between two very close surfaces also in motion. Using the asymptotic expansion method we formally justify two models, a lubrication model and a shallow water model, depending on the boundary conditions imposed. Finally, we discuss under what conditions each of the models would be applicable.

Published
2021
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212. Downflowing umbral flashes as an evidence of standing waves in sunspot umbrae

Author

Felipe, T., Henriques, V. M. J., Rodríguez, J. de la Cruz, and Socas-Navarro, H.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Umbral flashes are sudden brightenings commonly visible in the core of chromospheric lines. Theoretical and numerical modeling suggest that they are produced by the propagation of shock waves. According to these models and early observations, umbral flashes are associated with upflows. However, recent studies have reported umbral flashes in downflowing atmospheres. We aim to understand the origin of downflowing umbral flashes. We explore how the existence of standing waves in the umbral chromosphere impacts the generation of flashed profiles. We performed numerical simulations of wave propagation in a sunspot umbra with the code MANCHA. The Stokes profiles of the Ca II 8542 \AA\ line were synthesized with NICOLE. For freely-propagating waves, the chromospheric temperature enhancements of the oscillations are in phase with velocity upflows. In this case, the intensity core of the Ca II 8542 \AA\ atmosphere is heated during the upflowing stage of the oscillation. If we consider a different scenario with a resonant cavity, the wave reflections at the sharp temperature gradient of the transition region lead to standing oscillations. In this situation, temperature fluctuations are shifted backward and temperature enhancements partially coincide with the downflowing stage of the oscillation. In umbral flashes produced by standing oscillations, the reversal of the emission feature is produced when the oscillation is downflowing. The chromospheric temperature keeps increasing while the atmosphere is changing from a downflow to an upflow. During the appearance of flashed Ca II 8542 \AA\ cores, the atmosphere is upflowing most of the time, and only 38\% of the flashed profiles are associated with downflows. We find a scenario that remarkably explains the recent empirical findings of downflowing umbral flashes as a natural consequence of the presence of standing oscillations above sunspot umbrae., Comment: Letter accepted for publication in A&A

Published
2021
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213. Deep-Learning based Reconstruction of the Shower Maximum $X_{\mathrm{max}}$ using the Water-Cherenkov Detectors of the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Velázquez, J. C. Arteaga, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Orchera, P. G. Brichetto, Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Santos, D. Correia dos, Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Palma, F., de Souza, V., De Vito, E., del Río, M., Deligny, O., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, J. M., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Hamal, P., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Janecek, P., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Kunka, N., Lago, B. L., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lu, L., Luce, Q., Lucero, A., Lundquist, J. P., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nasr-Esfahani, A., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Martins, E. E. Pereira, Armand, J. Perez, Bertolli, C. Pérez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Segreto, A., Sehgal, S., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Taricco, C., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valore, L., Varela, E., C., V. Varma K., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watanabe, C., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., and Zepeda, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract

The atmospheric depth of the air shower maximum $X_{\mathrm{max}}$ is an observable commonly used for the determination of the nuclear mass composition of ultra-high energy cosmic rays. Direct measurements of $X_{\mathrm{max}}$ are performed using observations of the longitudinal shower development with fluorescence telescopes. At the same time, several methods have been proposed for an indirect estimation of $X_{\mathrm{max}}$ from the characteristics of the shower particles registered with surface detector arrays. In this paper, we present a deep neural network (DNN) for the estimation of $X_{\mathrm{max}}$. The reconstruction relies on the signals induced by shower particles in the ground based water-Cherenkov detectors of the Pierre Auger Observatory. The network architecture features recurrent long short-term memory layers to process the temporal structure of signals and hexagonal convolutions to exploit the symmetry of the surface detector array. We evaluate the performance of the network using air showers simulated with three different hadronic interaction models. Thereafter, we account for long-term detector effects and calibrate the reconstructed $X_{\mathrm{max}}$ using fluorescence measurements. Finally, we show that the event-by-event resolution in the reconstruction of the shower maximum improves with increasing shower energy and reaches less than $25~\mathrm{g/cm^{2}}$ at energies above $2\times 10^{19}~\mathrm{eV}$., Comment: Published version, 29 pages, 12 figures

Published
2021
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215. Radiometric and noise characteristics of InAs-rich T2SL MWIR pin photodiodes

Author

Giard E., Taalat R., Delmas M., Rodriguez J.-B., Christol P., and Ribet-Mohamed I.

Subjects
type-ii superlattice, photodiode, midwave infrared, quantum efficiency, noise, Applied optics. Photonics, TA1501-1820, Optics. Light, QC350-467
Abstract

We present a full characterization of the radiometric performances of a type-II InAs/GaSb superlattice pin photodiode operating in the mid-wavelength infrared domain. We first focused our attention on quantum efficiency, responsivity and angular response measurements: quantum efficiency reaches 23% at λ = 2.1 µm for 1 µm thick structure. Noise under illumination measurements are also reported: noise is limited by the Schottky contribution for reverse bias voltage smaller than 1.2 V. The specific detectivity, estimated for 2π field-of-view and 333 K background temperature, was determined equal to 2.29 × 1010 Jones for -0,8 V bias voltage and 77 K operating temperature.

Published
2014
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217. Calibration of the underground muon detector of the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Velázquez, J. C. Arteaga, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Orchera, P. G. Brichetto, Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Santos, D. Correia dos, Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Palma, F., de Souza, V., De Vito, E., del Río, M., Deligny, O., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, J. M., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Hamal, P., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Janecek, P., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Kunka, N., Lago, B. L., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lu, L., Luce, Q., Lucero, A., Lundquist, J. P., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nasr-Esfahani, A., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Martins, E. E. Pereira, Armand, J. Perez, Bertolli, C. Pérez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Segreto, A., Sehgal, S., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Taricco, C., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valore, L., Varela, E., C., V. Varma K., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watanabe, C., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., and Zepeda, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

To obtain direct measurements of the muon content of extensive air showers with energy above $10^{16.5}$ eV, the Pierre Auger Observatory is currently being equipped with an underground muon detector (UMD), consisting of 219 10 $\mathrm{m^2}$-modules, each segmented into 64 scintillators coupled to silicon photomultipliers (SiPMs). Direct access to the shower muon content allows for the study of both of the composition of primary cosmic rays and of high-energy hadronic interactions in the forward direction. As the muon density can vary between tens of muons per m$^2$ close to the intersection of the shower axis with the ground to much less than one per m$^2$ when far away, the necessary broad dynamic range is achieved by the simultaneous implementation of two acquisition modes in the read-out electronics: the binary mode, tuned to count single muons, and the ADC mode, suited to measure a high number of them. In this work, we present the end-to-end calibration of the muon detector modules: first, the SiPMs are calibrated by means of the binary channel, and then, the ADC channel is calibrated using atmospheric muons, detected in parallel to the shower data acquisition. The laboratory and field measurements performed to develop the implementation of the full calibration chain of both binary and ADC channels are presented and discussed. The calibration procedure is reliable to work with the high amount of channels in the UMD, which will be operated continuously, in changing environmental conditions, for several years., Comment: Published version, 25 pages, 12 figures, 0 tables

Published
2020
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218. An observationally-constrained model of strong magnetic reconnection in the solar chromosphere. Atmospheric stratification and estimates of heating rates

Author

Baso, C. J. Díaz, Rodríguez, J. de la Cruz, and Leenaarts, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics
Abstract

The evolution of the photospheric magnetic field plays a key role in the energy transport into the chromosphere and the corona. In active regions, newly emerging magnetic flux interacts with the pre-existent magnetic field, which can lead to reconnection events that convert magnetic energy to thermal energy. We aim to study the heating caused by a strong reconnection event that was triggered by magnetic flux cancellation. We use imaging-spectropolarimetric data in the Fe I 6301A, Fe I 6302A, Ca II 8542A and Ca II K obtained with the CRISP and CHROMIS instruments at the Swedish 1-m Solar Telescope. This data was inverted using multi-atom, multi-line non-LTE inversions using the STiC code. The inversion yielded a three-dimensional model of the reconnection event and surrounding atmosphere, including temperature, velocity, microturbulence, magnetic file configuration, and the radiative loss rate. The model atmosphere shows the emergence of magnetic loops with a size of several arcsecs into a pre-existing predominantly unipolar field. Where the reconnection region is expected to be, we see an increase in the chromospheric temperature of roughly 2000 K as well as bidirectional flows of the order of 10 km s$^{-1}$ emanating from the region. We see bright blobs of roughly 0.2 arcsec diameter in the Ca II K moving at a plane-of-the-sky velocity of order 100 km s$^{-1}$ and a blueshift of 100 km s$^{-1}$, which we interpret as plasmoids ejected from the same region. This evidence is consistent with theoretical models of reconnection and we thus conclude that reconnection is taking place. The chromospheric radiative losses at the reconnection site in our inferred model are as high as 160 kW m$^{-2}$, providing a quantitative constraint on theoretical models that aim to simulate reconnection caused by flux emergence in the chromosphere., Comment: 13 pages, 12 figures, accepted for publication in A&A

Published
2020
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219. Detection of short high-energy transients in the localuniverse with SVOM/ECLAIRs

Author

Arcier, B., Atteia, JL., Godet, O., Mate, S., Guillot, S., Dagoneau, N., Rodriguez, J., Gotz, D., Schanne, S., and Bernardini, M. G.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract

The coincidental detection of the gravitational wave event GW 170817 and the associated gamma-ray burst GRB 170817A marked the advent of multi-messenger astronomy and represented a milestone in the study of GRBs. In this context, the launch of SVOM in mid-2022, with its two wide-field high-energy instruments ECLAIRs and GRM, will foster the possibilities of coincidental transient detection with gravitational waves and gamma-rays events. The purpose of this paper is to assess the ability of SVOM/ECLAIRs to detect and quickly characterize high-energy transients in the local Universe (z<0.3), and to discuss the contribution of this instrument to multi-messenger astronomy and to gamma-ray burst(GRB) astrophysics in the 2020s. A list of local HE transients, along with their main characteristics, is constructed through an extensive literature survey. The detectability of these transients with ECLAIRs is assessed with detailed simulations using tools developed for the SVOM mission, including a GEANT4 simulation of the energy response and a simulated trigger algorithm representative of the onboard trigger algorithm. The SNR for almost all detections will be sufficiently high to allow the on-board ECLAIRs trigger algorithm to detect and derive the localisation of the transient, transmitting it to the SVOM satellite and ground-based instruments. Coupled with the anti-solar pointing strategy of SVOM, this will enable an optimal follow-up of the events, allowing the observation of their afterglows, supernovae/kilonovae counterparts, and host galaxies. We conclude the paper with a discussion of the unique contribution expected from SVOM and of the possibility of simultaneous GW detection for each type of transient in our sample.

Published
2020
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220. INTEGRAL discovery of a high-energy tail in the microquasar Cygnus X-3

Author

Cangemi, F., Rodriguez, J., Grinberg, V., Belmont, R., Laurent, P., and Wilms, J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The X-ray spectra of X-ray binaries are dominated by emission of either soft or hard X-rays which defines their soft and hard spectral states. Cygnus X-3 is amongst the list of X-ray binaries that show quite complex behavior, with various distinct spectral states. Because of its softness and intrinsic low flux above typically 50 keV, very little is known about the hard X/soft gamma-ray (100-1000 keV) emission in Cygnus X-3. Using the whole INTEGRAL data base, we aim to explore the 3-1000 keV spectra of Cygnus X-3. This allows to probe this region with the highest sensitivity ever, and search for the potential signature of a high-energy non-thermal component as sometimes seen in other sources. Our work is based on state classification carried out in previous studies with data from the Rossi X-Ray Timing Explorer. We extend this classification to the whole INTEGRAL data set and perform a long-term state-resolved spectral analysis. Six stacked spectra were obtained using 16 years of data from JEM-X, ISGRI, and SPI. We extract stacked images in three different energy bands, and detect the source up to 200 keV. In the hardest states, our phenomenological approach reveals the presence of an component > 50 keV in addition to the component usually interpreted as thermal Comptonization. We apply a more physical model of hybrid thermal/nonthermal corona to characterize this component and compare our results with those of previous studies. Our modeling indicates a more efficient acceleration of electrons in states where major ejections are observed. We find a dependence of the photon index of the power law as a function of the strong orbital modulation of the source in the Flaring InterMediate (FIM) state. This dependence could be due to a higher absorption when Cygnus X-3 is behind its companion. However, the uncertainties on the density column prevent us from drawing conclusions., Comment: Accepted for a publication in A&A, 14 pages, 7 figures, 4 tables

Published
2020
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221. Design, upgrade and characterization of the silicon photomultiplier front-end for the AMIGA detector at the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, J. M., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Lago, B. L., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Luce, Q., Lucero, A., Lundquist, J. P., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valore, L., Varela, E., C., V. Varma K., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., and Zepeda, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract

AMIGA (Auger Muons and Infill for the Ground Array) is an upgrade of the Pierre Auger Observatory to complement the study of ultra-high-energy cosmic rays (UHECR) by measuring the muon content of extensive air showers (EAS). It consists of an array of 61 water Cherenkov detectors on a denser spacing in combination with underground scintillation detectors used for muon density measurement. Each detector is composed of three scintillation modules, with 10 m$^2$ detection area per module, buried at 2.3 m depth, resulting in a total detection area of 30 m$^2$. Silicon photomultiplier sensors (SiPM) measure the amount of scintillation light generated by charged particles traversing the modules. In this paper, the design of the front-end electronics to process the signals of those SiPMs and test results from the laboratory and from the Pierre Auger Observatory are described. Compared to our previous prototype, the new electronics shows a higher performance, higher efficiency and lower power consumption, and it has a new acquisition system with increased dynamic range that allows measurements closer to the shower core. The new acquisition system is based on the measurement of the total charge signal that the muonic component of the cosmic ray shower generates in the detector., Comment: 40 pages, 33 figures

Published
2020
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222. Monopolar and dipolar relaxation in spin ice Ho$_2$Ti$_2$O$_7$

Author

Wang, Yishu, Reeder, T., Karaki, Y., Kindervater, J., Halloran, T., Maliszewskyj, N., Qiu, Yiming, Rodriguez, J. A., Gladchenko, S., Koohpayeh, S. M., Nakatsuji, S., and Broholm, C.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

When degenerate states are separated by large energy barriers, the approach to thermal equilibrium can be slow enough that physical properties are defined by the thermalization process rather than the equilibrium. The exploration of thermalization pushes experimental boundaries and provides refreshing insights into atomic scale correlations and processes that impact steady state dynamics and prospects for realizing solid state quantum entanglement. We present a comprehensive study of magnetic relaxation in Ho$_2$Ti$_2$O$_7$ based on frequency-dependent susceptibility measurements and neutron diffraction studies of the real-time atomic-scale response to field quenches. Covering nearly ten decades in time scales, these experiments uncover two distinct relaxation processes that dominate in different temperature regimes. At low temperatures (0.6K

Published
2020
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223. Characterization of Folding and Stretching in Mixing Enhancements

Author

Rodríguez, J., Chen, D., and Guzmán, A. M.

Subjects
Physics - Fluid Dynamics
Abstract

This research paper presents a 2D numerical model of an electrokinetic T-junction micromixer based on the stretching and folding theory presented by Ottino. Particle deformation was considered by simulating 2 $\mu m$ massless particles as 8-point square cells. Furthermore, stretching and folding definitions are proposed, compatible with a Lagrangian particle approach. Moreover, mixing homogeneity and consistency were measured in a 200 $\mu m$ square region of interest neighboring the outlet. Statistical analysis of the exiting mixing homogeneity at four different electric field conditions (93.5 V/cm, 109.8 V/cm, 126 V/cm and 117.9 V/cm, corresponding to a 23V, 27V, 29V and 31V potential difference) show that mixing consistency and homogeneity are not always increased with a higher electric field intensity, even after electrokinetic instabilities are formed, as increasingly unstable flow conditions decrease the ratio of folding to stretching ($m$), hindering the interaction between substances. Finally, an optimal proportion of stretching to folding was found for maximizing mixing efficiency at $m =0.0045$., Comment: 17 pages, 7 figures

Published
2020

224. Line formation of He I D3 and He I 10830 {\AA} in a small-scale reconnection event

Author

Libbrecht, T., Bjørgen, J. P., Leenaarts, J., Rodríguez, J. de la Cruz, Hansteen, V., and Joshi, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Aims. We aim to explain line formation of He I D3 and He I 10830 {\AA} in small-scale reconnection events. Methods. We make use of a simulated Ellerman bomb (EB), present in a Bifrost-generated radiative Magnetohydrodynamics (rMHD) snapshot. The resulting He I D3 and He I 10830 \AA\ line intensities are synthesized in 3D using the non-LTE Multi3D code. We compare the synthetic helium spectra with observed SST/TRIPPEL raster scans of EBs in He I 10830 \AA\ and He I D3. Results. Emission in He I D3 and He I 10830 \AA\ is formed in a thin shell around the EB at a height of $\sim 0.8$ Mm while the He I D3 absorption is formed above the EB at $\sim 4$ Mm. The height at which the emission is formed corresponds to the lower boundary of the EB, where the temperature increases rapidly from $6\cdot 10^3$ K to $10^6$ K. The opacity in He I D3 and He I 10830 \AA\ is generated via photoionization-recombination driven by EUV radiation that is locally generated in the EB at temperatures in the range of $2\cdot 10^4 - 2\cdot 10^6$ K and electron densities between $10^{11}$ and $10^{13}$ cm$^{-3}$. The synthetic emission signals are a result of coupling to local conditions in a thin shell around the EB, with temperatures between $7\cdot 10^3$ and $10^4$ K and electron densities ranging from $\sim 10^{12}$ to $10^{13}$ cm$^{-3}$. Hence, both strong non-LTE as well as thermal processes play a role in the formation of He I D3 and He I 10830 \AA\ in the synthetic EB/UV burst that we studied. Conclusions. In conclusion, the synthetic He I D3 and He I 10830 \AA\ emission signatures are an indicator of temperatures of at least $2\cdot 10^4$ K and in this case as high as $\sim 10^6$ K., Comment: 12 pages, 13 figures, submitted to A&A

Published
2020
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225. Investigating the mini and giant radio flare episodes of Cygnus X-3

Author

Egron, E., Pellizzoni, A., Righini, S., Giroletti, M., Koljonen, K., Pottschmidt, K., Trushkin, S., Lobina, J., Pilia, M., Wilms, J., Corbel, S., Grinberg, V., Loru, S., Trois, A., Rodriguez, J., Lähteenmäki, A., Tornikoski, M., Enestam, S., and Järvelä, E.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The microquasar Cygnus X-3 underwent a giant radio flare in April 2017, reaching a maximum flux of $\sim 16.5$ Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6 and 24.1 GHz, in parallel to the Mets\"ahovi radio telescope at 37 GHz, from 4 to 11 April 2017. We observe a spectral steepening from $\alpha = 0.2$ to 0.5 (with $S_{\nu} \propto \nu^{-\alpha}$) within 6 h around the epoch of the peak maximum of the flare, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of Cyg X-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994, 1995, 2002 and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phase $\phi \sim 0.5$ (orbital inferior conjunction). On the other hand the light curves of the mini-flares observed at $15-22$ GHz peak at $\phi \sim 0$, except for the 2016 light curve which is shifted of 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state)., Comment: 15 pages, 4 figures, accepted for publication in the Astrophysical Journal

Published
2020
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226. A search for ultra high energy neutrinos from TXS 0506+056 using the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Calcagni, L., Cancio, A., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Dhital, N., Di Matteo, A., Dobrigkeit, C., D'Olivo, J. C., Dorosti, Q., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Halliday, R., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Mezek, G. Kukec, Lago, B. L., LaHurd, D., Lang, R. G., Langner, N., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lorek, R., Luce, Q., Lucero, A., Payeras, A. Machado, Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mockler, D., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C. M., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulte, J., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valore, L., Varela, E., Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., and Ziolkowski, M.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Results of a search for ultra-high-energy neutrinos with the Pierre Auger Observatory from the direction of the blazar TXS 0506+056 are presented. They were obtained as part of the follow-up that stemmed from the detection of high-energy neutrinos and gamma rays with IceCube, \textit{Fermi}-LAT, MAGIC, and other detectors of electromagnetic radiation in several bands. The Pierre Auger Observatory is sensitive to neutrinos in the energy range from 100 PeV to 100 EeV and in the zenith angle range from $\theta=60^\circ$ to $\theta=95^\circ$, where the zenith angle is measured from the vertical direction. No neutrinos from the direction of TXS 0506+056 have been found. The results were analyzed in three periods: One of 6 months around the detection of IceCube-170922A, coinciding with a flare period of TXS 0506+056, a second one of 110 days during which the IceCube collaboration found an excess of 13 neutrinos from a direction compatible with TXS 0506+056, and a third one from 2004 January 1 up to 2018 August 31, over which the Pierre Auger Observatory has been taking data. The sensitivity of the Observatory is addressed for different spectral indices by considering the fluxes that would induce a single expected event during the observation period. For indices compatible with those measured by the IceCube collaboration the expected number of neutrinos at the Observatory is well-below one. Spectral indices as hard as 1.5 would have to apply in this energy range to expect a single event to have been detected., Comment: Published version, 4 figures

Published
2020
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227. Observation of Yu-Shiba-Rusinov states in superconducting graphene

Author

Río, E. Cortés-del, Lado, J. L., Cherkez, V., Mallet, P., Veuillen, J-Y., Cuevas, J. C., Gómez-Rodríguez, J. M., Fernández-Rossier, J., and Brihuega, I.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Abstract

When magnetic atoms are inserted inside a superconductor, the superconducting order is locally depleted as a result of the antagonistic nature of magnetism and superconductivity1. Thereby, distinctive spectral features, known as Yu-Shiba-Rusinov states, appear inside the superconducting gap2-4. The search for Yu-Shiba-Rusinov states in different materials is intense, as they can be used as building blocks to promote Majorana modes5 suitable for topological quantum computing6. Here we report the first realization of Yu-Shiba-Rusinov states in graphene, a non-superconducting 2D material, and without the participation of magnetic atoms. We induce superconductivity in graphene by proximity effect7-9 brought by adsorbing nanometer scale superconducting Pb islands. Using scanning tunneling microscopy and spectroscopy we measure the superconducting proximity gap in graphene and we visualize Yu-Shiba-Rusinov states in graphene grain boundaries. Our results reveal the very special nature of those Yu-Shiba-Rusinov states, which extends more than 20 nm away from the grain boundaries. These observations provide the long sought experimental confirmation that graphene grain boundaries host local magnetic moments10-14 and constitute the first observation of Yu-Shiba-Rusinov states in a chemically pure system.

Published
2020

228. Onboard catalogue of known X-ray sources for SVOM/ECLAIRs

Author

Dagoneau, N., Schanne, S., Rodriguez, J., Atteia, J. -L., and Cordier, B.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The SVOM mission under development will carry various instruments, and in particular the coded-mask telescope ECLAIRs, with a large field of view of about 2 sr, operating in the 4--150 keV energy band, whose goal is to detect high energy transients such as gamma-ray bursts. The trigger software onboard ECLAIRs will search for new hard X-ray sources appearing in the sky, as well as peculiar behaviour (e.g. strong outbursts) from known sources, in order to repoint the satellite to perform follow-up observations with its onboard narrow field of view instruments. The presence of known X-ray sources must be disentangled from the appearance of new sources. This is done with the help of an onboard source catalogue, which we present in this paper. As an input we use catalogues of X-ray sources detected by Swift/BAT and MAXI/GSC and we study the influence of the sources on ECLAIRs' background level and on the quality of the sky image reconstruction process. We show that the influence of the sources depends on the pointing direction on the sky, on the energy band and on the exposure time. In the Galactic centre, the known sources contribution largely dominates the cosmic X-ray background, which is, on the contrary, the main background in sky regions empty of strong sources. We also demonstrate the need to clean the sources contributions in order to maintain a low noise level in the sky images and to keep the threshold applied for the detection of new sources as low as possible, without introducing false triggers. We briefly describe one of our cleaning methods and its challenges. Finally, we present the overall structure of the onboard catalogue and the way it will be used to perform the source cleaning and disentangle the detections of new sources from outbursts of known sources., Comment: Accepted in Astronomy & Astrophysics, section 13. Astronomical instrumentation. Additional data to be archived at CDS

Published
2020
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229. Power spectrum of turbulent convection in the solar photosphere

Author

Chaouche, L. Yelles, Cameron, R. H., Solanki, S. K., Riethmüller, T. L., Anusha, L. S., Witzke, V., Shapiro, A. I., Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., van Noort, M., Rodríguez, J. Blanco, Iniesta, J. C. Del Toro, Suárez, D. Orozco, Schmidt, W., Pillet, V. Martínez, and Knölker, M.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The solar photosphere provides us with a laboratory for understanding turbulence in a layer where the fundamental processes of transport vary rapidly and a strongly superadiabatic region lies very closely to a subadiabatic layer. Our tools for probing the turbulence are high-resolution spectropolarimetric observations such as have recently been obtained with the two sunrise missions, and numerical simulations. Our aim is to study photospheric turbulence with the help of Fourier power spectra that we compute from observations and simulations. We also attempt to explain some properties of the photospheric overshooting flow with the help of its governing equations and simulations. We find that quiet-Sun observations and smeared simulations exhibit a power-law behavior in the subgranular range of their Doppler velocity power spectra with an index of$~\approx -2$. The unsmeared simulations exhibit a power-law index of$~\approx -2.25$. The smearing considerably reduces the extent of the power-law-like portion of the spectra. Therefore, the limited spatial resolution in some observations might eventually result in larger uncertainties in the estimation of the power-law indices. The simulated vertical velocity power spectra as a function of height show a rapid change in the power-law index from the solar surface to $300$~km above it. A scale-dependent transport of the vertical momentum occurs. At smaller scales, the vertical momentum is more efficiently transported sideways than at larger scales. This results in less vertical velocity power transported upward at small scales than at larger scales and produces a progressively steeper vertical velocity power law below $180$ km. Above this height, the gravity work progressively gains importance at all scales, making the atmosphere progressively more hydrostatic and resulting in a gradually less steep power law., Comment: 10 pages, 7 figures, Accepted in A and A

Published
2020
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230. CzeV1731: The unique doubly eclipsing quadruple system

Author

Zasche, P., Henzl, Z., Lehmann, H., Pepper, J., Powell, B. P., Kostov, V. B., Barclay, T., Wolf, M., Kucakova, H., Uhlar, R., Masek, M., Palafouta, S., Gazeas, K., Stassun, K. G., Gaudi, B. S., Rodriguez, J. E., and Stevens, D. J.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We report the discovery of the relatively bright (V = 10.5 mag), doubly eclipsing 2+2 quadruple system CzeV1731. This is the third known system of its kind, in which the masses are determined for all four stars and both the inner and outer orbits are characterized. The inner eclipsing binaries are well-detached systems moving on circular orbits: pair A with period PA = 4.10843 d and pair B with PB = 4.67552 d. The inner binaries contain very similar components (q = 1.0), making the whole system a so-called double twin. The stars in pair B have slightly larger luminosities and masses and pair A shows deeper eclipses. All four components are main-sequence stars of F/G spectral type. The mutual orbit of the two pairs around the system barycenter has a period of about 34 yr and an eccentricity of about 0.38. However, further observations are needed to reveal the overall architecture of the whole system, including the mutual inclinations of all orbits. This is a promising target for interferometry to detect the double at about 59 mas and dMbol < 1 mag. (The RV and ETV data available via CDS), Comment: 5 pages, 6 figures, 2 Tables, published in: 2020A&A...642A..63Z

Published
2020
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231. Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

Author

Consortium, The Cherenkov Telescope Array, Abdalla, H., Abe, H., Acero, F., Acharyya, A., Adam, R., Agudo, I., Aguirre-Santaella, A., Alfaro, R., Alfaro, J., Alispach, C., Aloisio, R., B, R. Alves, Amati, L., Amato, E., Ambrosi, G., Angüner, E. O., Araudo, A., Armstrong, T., Arqueros, F., Arrabito, L., Asano, K., Ascasíbar, Y., Ashley, M., Backes, M., Balazs, C., Balbo, M., Balmaverde, B., Larriva, A. Baquero, Martins, V. Barbosa, Barkov, M., Baroncelli, L., de Almeida, U. Barres, Barrio, J. A., Batista, P., Becerra, J., Becherini, Y., Beck, G., Tjus, J. Becker, Belmont, R., Benbow, W., Bernardini, E., Berti, A., Berton, M., Bertucci, B., Beshley, V., Bi, B., Biasuzzi, B., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Bocchino, F., Boisson, C., Bolmont, J., Bonanno, G., Arbeletche, L. Bonneau, Bonnoli, G., Bordas, P., Bottacini, E., Böttcher, M., Bozhilov, V., Bregeon, J., Brill, A., Brown, A. M., Bruno, P., Bruno, A., Bulgarelli, A., Burton, M., Buscemi, M., Caccianiga, A., Cameron, R., Capasso, M., Caprai, M., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Carosi, R., Carosi, A., Casanova, S., Cascone, E., Cauz, D., Cerny, K., Cerruti, M., Chadwick, P., Chaty, S., Chen, A., Chernyakova, M., Chiaro, G., Chiavassa, A., Chytka, L., Conforti, V., Conte, F., Contreras, J. L., Coronado-Blazquez, J., Cortina, J., Costa, A., Costantini, H., Covino, S., Cristofari, P., Cuevas, O., D'Ammando, F., Daniel, M. K., Davies, J., Dazzi, F., De Angelis, A., de Lavergne, M. de Bony, De Caprio, V., Anjos, R. de Cássia dos, Pino, E. M. de Gouveia Dal, De Lotto, B., De Martino, D., de Naurois, M., Wilhelmi, E. de Oña, De Palma, F., de Souza, V., Delgado, C., Della Ceca, R., della Volpe, D., Depaoli, D., Di Girolamo, T., Di Pierro, F., Díaz, C., Díaz-Bahamondes, C., Diebold, S., Djannati-Ataï, A., Dmytriiev, A., Domínguez, A., Donini, A., Dorner, D., Doro, M., Dournaux, J., Dwarkadas, V. V., Ebr, J., Eckner, C., Einecke, S., Ekoume, T. R. N., Elsässer, D., Emery, G., Evoli, C., Fairbairn, M., Falceta-Goncalves, D., Fegan, S., Feng, Q., Ferrand, G., Fiandrini, E., Fiasson, A., Fioretti, V., Foffano, L., Fonseca, M. V., Font, L., Fontaine, G., Franco, F. J., Coromina, L. Freixas, Fukami, S., Fukazawa, Y., Fukui, Y., Gaggero, D., Galanti, G., Gammaldi, V., Garcia, E., Garczarczyk, M., Gascon, D., Gaug, M., Gent, A., Ghalumyan, A., Ghirlanda, G., Gianotti, F., Giarrusso, M., Giavitto, G., Giglietto, N., Giordano, F., Glicenstein, J., Goldoni, P., González, J. M., Gourgouliatos, K., Grabarczyk, T., Grandi, P., Granot, J., Grasso, D., Green, J., Grube, J., Gueta, O., Gunji, S., Halim, A., Harvey, M., Collado, T. Hassan, Hayashi, K., Heller, M., Cadena, S. Hernández, Hervet, O., Hinton, J., Hiroshima, N., Hnatyk, B., Hnatyk, R., Hoffmann, D., Hofmann, W., Holder, J., Horan, D., Hörandel, J., Horvath, P., Hovatta, T., Hrabovsky, M., Hrupec, D., Hughes, G., Hütten, M., Iarlori, M., Inada, T., Inoue, S., Insolia, A., Ionica, M., Iori, M., Jacquemont, M., Jamrozy, M., Janecek, P., Martínez, I. Jiménez, Jin, W., Jung-Richardt, I., Jurysek, J., Kaaret, P., Karas, V., Karkar, S., Kawanaka, N., Kerszberg, D., Khélifi, B., Kissmann, R., Knödlseder, J., Kobayashi, Y., Kohri, K., Komin, N., Kong, A., Kosack, K., Kubo, H., La Palombara, N., Lamanna, G., Lang, R. G., Lapington, J., Laporte, P., Lemoine-Goumard, M., Lenain, J., Leone, F., Leto, G., Leuschner, F., Lindfors, E., Lloyd, S., Lohse, T., Lombardi, S., Longo, F., Lopez, A., López, M., López-Coto, R., Loporchio, S., Lucarelli, F., Luque-Escamilla, P. L., Lyard, E., Maggio, C., Majczyna, A., Makariev, M., Mallamaci, M., Mandat, D., Maneva, G., Manganaro, M., Manicò, G., Marcowith, A., Marculewicz, M., Markoff, S., Marquez, P., Martí, J., Martinez, O., Martínez, M., Martínez, G., Martínez-Huerta, H., Maurin, G., Mazin, D., Mbarubucyeye, J. D., Miranda, D. Medina, Meyer, M., Micanovic, S., Miener, T., Minev, M., Miranda, J. M., Mitchell, A., Mizuno, T., Mode, B., Moderski, R., Mohrmann, L., Molina, E., Montaruli, T., Moralejo, A., Merino, J. Morales, Morcuende-Parrilla, D., Morselli, A., Mukherjee, R., Mundell, C., Murach, T., Muraishi, H., Nagai, A., Nakamori, T., Nemmen, R., Niemiec, J., Nieto, D., Nievas, M., Nikołajuk, M., Nishijima, K., Noda, K., Nosek, D., Nozaki, S., O'Brien, P., Ohira, Y., Ohishi, M., Oka, T., Ong, R. A., Orienti, M., Orito, R., Orlandini, M., Orlando, E., Osborne, J. P., Ostrowski, M., Oya, I., Pagliaro, A., Palatka, M., Paneque, D., Pantaleo, F. R., Paredes, J. M., Parmiggiani, N., Patricelli, B., Pavletić, L., Pe'er, A., Pech, M., Pecimotika, M., Peresano, M., Persic, M., Petruk, O., Pfrang, K., Piatteli, P., Pietropaolo, E., Pillera, R., Pilszyk, B., Pimentel, D., Pintore, F., Pita, S., Pohl, M., Poireau, V., Polo, M., Prado, R. R., Prast, J., Principe, G., Produit, N., Prokoph, H., Prouza, M., Przybilski, H., Pueschel, E., Pühlhofer, G., Pumo, M. L., Punch, M., Queiroz, F., Quirrenbach, A., Rando, R., Razzaque, S., Rebert, E., Recchia, S., Reichherzer, P., Reimer, O., Reimer, A., Renier, Y., Reposeur, T., Rhode, W., Ribeiro, D., Ribó, M., Richtler, T., Rico, J., Rieger, F., Rizi, V., Rodriguez, J., Fernandez, G. Rodriguez, Ramirez, J. C. Rodriguez, Vázquez, J. J. Rodríguez, Romano, P., Romeo, G., Roncadelli, M., Rosado, J., de Leon, A. Rosales, Rowell, G., Rudak, B., Rujopakarn, W., Russo, F., Sadeh, I., Saha, L., Saito, T., Greus, F. Salesa, Sanchez, D., Sánchez-Conde, M., Sangiorgi, P., Sano, H., Santander, M., Santos, E. M., Sanuy, A., Sarkar, S., Saturni, F. G., Sawangwit, U., Scherer, A., Schleicher, B., Schovanek, P., Schussler, F., Schwanke, U., Sciacca, E., Scuderi, S., Arroyo, M. Seglar, Sergijenko, O., Servillat, M., Seweryn, K., Shalchi, A., Sharma, P., Shellard, R. C., Siejkowski, H., Sinha, A., Sliusar, V., Slowikowska, A., Sokolenko, A., Sol, H., Specovius, A., Spencer, S., Spiga, D., Stamerra, A., Stanič, S., Starling, R., Stolarczyk, T., Straumann, U., Strišković, J., Suda, Y., Świerk, P., Tagliaferri, G., Takahashi, H., Takahashi, M., Tavecchio, F., Taylor, L., Tejedor, L. A., Temnikov, P., Terrier, R., Terzic, T., Testa, V., Tian, W., Tibaldo, L., Tonev, D., Torres, D. F., Torresi, E., Tosti, L., Tothill, N., Tovmassian, G., Travnicek, P., Truzzi, S., Tuossenel, F., Umana, G., Vacula, M., Vagelli, V., Valentino, M., Vallage, B., Vallania, P., van Eldik, C., Varner, G. S., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Veh, J., Vercellone, S., Vergani, S., Verguilov, V., Vettolani, G. P., Viana, A., Vigorito, C. F., Vitale, V., Vorobiov, S., Vovk, I., Vuillaume, T., Wagner, S. J., Walter, R., Watson, J., White, M., White, R., Wiemann, R., Wierzcholska, A., Will, M., Williams, D. A., Wischnewski, R., Wolter, A., Yamazaki, R., Yanagita, S., Yang, L., Yoshikoshi, T., Zacharias, M., Zaharijas, G., Zaric, D., Zavrtanik, M., Zavrtanik, D., Zech, A., Zechlin, H., Zhdanov, V. I., and Živec, M.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for $\gamma$-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of $\gamma$-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of $\gamma$-ray absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift $z=2$ and to constrain or detect $\gamma$-ray halos up to intergalactic-magnetic-field strengths of at least 0.3pG. Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from $\gamma$-ray astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of $\gamma$-ray cosmology., Comment: 71 pages (including affiliations and references), 13 figures, 6 tables. Accepted in JCAP; matches published version. Corresponding authors: Jonathan Biteau, Julien Lefaucheur, Humberto Martinez-Huerta, Manuel Meyer, Santiago Pita, Ievgen Vovk

Published
2020
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232. Atomic-scale control of graphene magnetism using hydrogen atoms

Author

González-Herrero, H., Gómez-Rodríguez, J. M., Mallet, P., Moaied, M., Palacios, J. J., Salgado, C., Ugeda, M. M., Veuillen, J. Y., Yndurain, F., and Brihuega, I.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Isolated hydrogen atoms absorbed on graphene are predicted to induce magnetic moments. Here we demonstrate that the adsorption of a single hydrogen atom on graphene induces a magnetic moment characterized by a ~20 meV spin-split state at the Fermi energy. Our scanning tunneling microscopy (STM) experiments, complemented by first-principles calculations, show that such a spin-polarized state is essentially localized on the carbon sublattice complementary to the one where the H atom is chemisorbed. This atomically modulated spin-texture, which extends several nanometers away from the H atom, drives the direct coupling between the magnetic moments at unusually long distances. Using the STM tip to manipulate H atoms with atomic precision, we demonstrate the possibility to tailor the magnetism of selected graphene regions.

Published
2020
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233. Effect of Self-Lubricating Carbon Materials on the Tribological Performance of Ultra-High-Molecular-Weight Polyethylene

Author

Camacho, N., Escobedo-Rodríguez, J. D., Alvarado-Orozco, J. M., and Mondragón-Rodríguez, G. C.

Subjects
Condensed Matter - Materials Science
Abstract

Ultra-high-molecular-weight polyethylene (UHMWPE) has been the gold standard for total knee replacements. Due to the knee's natural movements, UHMWPE wear debris production is inevitable. The debris, at the micron and submicron level, results in the joint's mechanical instability, reduced mobility, increased pain, and implant loosening. Wear debris production has been linked to UHMWPE mechanical properties; therefore, improvements to increase the UHMWPE mechanical properties will impact the component's longevity. Here, TiC coating and multiwalled carbon nanotubes (MWCNTs) were used to decrease the UHMWPE wear. After 400,000 cycles, the UHMWPE-MWCNT diminishes the mass loss compared to UHMWPE, and the combination with TiC decreased the material loss by ~ 43.7 % compared to the reference pair. Cold-flow and burnishing were the predominant wear modes., Comment: 9 p\'aginas

Published
2020

234. Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

Author

Bouma, L. G., Hartman, J. D., Brahm, R., Evans, P., Collins, K. A., Zhou, G., Sarkis, P., Quinn, S. N., de Leon, J., Livingston, J., Bergmann, C., Stassun, K. G., Bhatti, W., Winn, J. N., Bakos, G. Á, Abe, L., Crouzet, N., Dransfield, G., Guillot, T., Marie-Sainte, W., Mékarnia, D., Triaud, A. H. M. J., Tinney, C. G., Henning, T., Espinoza, N., Jordán, A., Barbieri, M., Nandakumar, S., Trifonov, T., Vines, J. I., Vuckovic, M., Ziegler, C., Law, N., Mann, A. W., Ricker, G. R., Vanderspek, R., Seager, S., Jenkins, J. M., Burke, C. J., Dragomir, D., Levine, A. M., Quintana, E. V., Rodriguez, J. E., Smith, J. C., and Wohler, B.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA TESS mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a $T=9.9$ mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore $35^{+11}_{-5}$ million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color-magnitude diagram, we find that the planet has an orbital period of $8.3\,{\rm d}$ and is slightly smaller than Jupiter ($R_{\rm p} = 0.77^{+0.09}_{-0.07} \,R_{\rm Jup}$). From radial velocity monitoring, we limit $M_{\rm p}\sin i$ to less than 1.20 $M_{\rm Jup}$ (3-$\sigma$). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multi-color photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time., Comment: AJ accepted. Figure 11 is my favorite. Comments welcome!

Published
2020
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235. Modeling and simulation of the R5912 photomultiplier for the LAGO project

Author

Hernández-Barajas, S., León-Carreño, Y., Peña-Rodríguez, J., Núñez, L. A., and collaboration, LAGO

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

We present the results of modeling and simulating the Hamamatsu R5912 photomultiplier tube that is used in most of the sites of the Latin American Giant Observatory (LAGO). The model was compared with data of in-operation water Cherenkov detectors (WCD) installed at Bucaramanga-Colombia and Bariloche-Argentina. The LAGO project is an international experiment that spans across Latin America at different altitudes joining more than 35 institutions of 11 countries. It is mainly oriented to basic research on gamma-ray bursts and space weather phenomena. The LAGO network consists of single or small arrays of WCDs composed mainly by a photomultiplier tube and a readout electronics that acquires single-particle or extensive air shower events triggered by the interaction of cosmic rays with the Earth atmosphere.

Published
2020

236. Non-LTE inversions of a confined X2.2 flare: I. Vector magnetic field in the photosphere and chromosphere

Author

Vissers, G. J. M., Danilovic, S., Rodriguez, J. de la Cruz, Leenaarts, J., Morosin, R., Baso, C. J. Diaz, Reid, A., Pomoell, J., Price, D. J., and Inoue, S.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Obtaining the magnetic field vector accurately in the solar atmosphere is essential for studying changes in field topology during flares and to reliably model space weather. We tackle this problem by applying various inversion methods to a confined X2.2 flare in NOAA AR 12673 on September 6, 2017, comparing the photospheric and chromospheric magnetic field vector with those from two numerical models of this event. We obtain the photospheric field from Milne-Eddington (ME) and (non-)local thermal equilibrium (non-LTE) inversions of Hinode SOT/SP Fe I 6301.5{\AA} and 6302.5{\AA}. The chromospheric field is obtained from a spatially-regularised weak field approximation (WFA) and non-LTE inversions of Ca II 8542{\AA} observed with CRISP at the Swedish 1-m Solar Telescope. The LTE- and non-LTE-inferred photospheric field components are strongly correlated throughout the atmosphere, with stronger field and higher temperatures in the non-LTE inversions. For the chromospheric field, the non-LTE inversions correlate well with the spatially-regularised WFA. We find strong-field patches of over 4.5 kG in the photosphere, co-located with similar concentrations exceeding 3 kG in the chromosphere. The obtained field strengths are up to 2-3 times higher than in the numerical models, with more concentrated and structured photosphere-to-chromosphere shear close to the polarity inversion line. The LTE and non-LTE Fe I inversions yield essentially the same photospheric field, while ME inversions fail to reproduce the field vector orientation where Fe I is in emission. Our inversions confirm the locations of flux rope footpoints that are predicted by numerical models. However, pre-processing and lower spatial resolution lead to weaker and smoother field in the models than what the data indicate. This emphasises the need for higher spatial resolution in the models to better constrain pre-eruptive flux ropes., Comment: Submitted to Astronomy & Astrophysics. 16 pages, 8 figures

Published
2020
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237. Bow-shocks, nova shells, disc winds and tilted discs: The Nova-Like V341 Ara Has It All

Author

Segura, N. Castro, Knigge, C., Acosta-Pulido, J. A., Altamirano, D., del Palacio, S., Santisteban, J. V. Hernandez, Pahari, M., Rodriguez-Gil, P., Belardi, C., Buckley, D. A. H., Burleigh, M. R., Childress, M., Fender, R. P., Hewitt, D. M., James, D. J., Kuhn, R. B., Kuin, N. P. M., Pepper, J., Ponomareva, A. A., Pretorius, M. L., Rodríguez, J. E., Stassun, K. G., Williams, D. R. A., and Woudt, P. A.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

V341 Ara was recently recognised as one of the closest (d ~ 150 pc) and brightest (V~ 10) nova-like cataclysmic variables. This unique system is surrounded by a bright emission nebula, likely to be the remnant of a recent nova eruption. Embedded within this nebula is a prominent bow-shock, where the system's accretion disc wind runs into its own nova shell. In order to establish its fundamental properties, we present the first comprehensive multi-wavelength study of the system. Long-term photometry reveals quasi-periodic, super-orbital variations with a characteristic time-scale of 10-16 days and typical amplitude of ~1 mag. High-cadence photometry from TESS reveals for the first time both the orbital period and a "negative superhump" period. The latter is usually interpreted as the signature of a tilted accretion disc. We propose a recently developed disc instability model as a plausible explanation for the photometric behaviour. In our spectroscopic data, we clearly detect anti-phased absorption and emission line components. Their radial velocities suggest a high mass ratio, which in turn implies an unusually low white dwarf mass. We also constrain the wind mass-loss rate of the system from the spatially resolved [O iii] emission produced in the bow-shock; this can be used to test and calibrate accretion disc wind models. We suggest a possible association between V341 Ara and a "guest star" mentioned in Chinese historical records in AD1240. If this marks the date of the system's nova eruption, V341 Ara would be the oldest recovered nova of its class and an excellent laboratory for testing nova theory., Comment: Accepted in MNRAS

Published
2020
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238. Measurement of the cosmic-ray energy spectrum above $2.5{\times} 10^{18}$ eV using the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Castillo, J. Alvarez, Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blanco, A., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Calcagni, L., Cancio, A., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Dembinski, H., Dhital, N., Di Giulio, C., Di Matteo, A., Castro, M. L. Díaz, Dobrigkeit, C., D'Olivo, J. C., Dorosti, Q., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Halliday, R., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Mezek, G. Kukec, Lago, B. L., LaHurd, D., Lang, R. G., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lorek, R., Luce, Q., Lucero, A., Payeras, A. Machado, Malacari, M., Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mockler, D., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Nguyen, P. H., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Panetta, M. P., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Peters, C., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Fernandez, G. Rodriguez, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulz, A., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Elipe, G. Torralba, Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Urban, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valiño, I., Valore, L., van Vliet, A., Varela, E., Cárdenas, B. Vargas, Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Villaseñor, L., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., Ziolkowski, M., and Zuccarello, F.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report a measurement of the energy spectrum of cosmic rays for energies above $2.5 {\times} 10^{18}~$eV based on 215,030 events recorded with zenith angles below $60^\circ$. A key feature of the work is that the estimates of the energies are independent of assumptions about the unknown hadronic physics or of the primary mass composition. The measurement is the most precise made hitherto with the accumulated exposure being so large that the measurements of the flux are dominated by systematic uncertainties except at energies above $5 {\times} 10^{19}~$eV. The principal conclusions are: (1) The flattening of the spectrum near $5 {\times} 10^{18}~$eV, the so-called "ankle", is confirmed. (2) The steepening of the spectrum at around $5 {\times} 10^{19}~$eV is confirmed. (3) A new feature has been identified in the spectrum: in the region above the ankle the spectral index $\gamma$ of the particle flux ($\propto E^{-\gamma}$) changes from $2.51 \pm 0.03~{\rm (stat.)} \pm 0.05~{\rm (sys.)}$ to $3.05 \pm 0.05~{\rm (stat.)} \pm 0.10~{\rm (sys.)}$ before changing sharply to $5.1 \pm 0.3~{\rm (stat.)} \pm 0.1~{\rm (sys.)}$ above $5 {\times} 10^{19}~$eV. (4) No evidence for any dependence of the spectrum on declination has been found other than a mild excess from the Southern Hemisphere that is consistent with the anisotropy observed above $8 {\times} 10^{18}~$eV., Comment: Published version; 16 figures, 6 table

Published
2020
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239. Features of the energy spectrum of cosmic rays above $2.5{\times} 10^{18}$ eV using the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Castillo, J. Alvarez, Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blanco, A., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Calcagni, L., Cancio, A., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Dembinski, H., Dhital, N., Di Giulio, C., Di Matteo, A., Castro, M. L. Díaz, Dobrigkeit, C., D'Olivo, J. C., Dorosti, Q., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Halliday, R., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Mezek, G. Kukec, Lago, B. L., LaHurd, D., Lang, R. G., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lorek, R., Luce, Q., Lucero, A., Payeras, A. Machado, Malacari, M., Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mockler, D., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Nguyen, P. H., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Panetta, M. P., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Peters, C., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Fernandez, G. Rodriguez, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulz, A., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Elipe, G. Torralba, Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Urban, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valiño, I., Valore, L., van Vliet, A., Varela, E., Cárdenas, B. Vargas, Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Villaseñor, L., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., Ziolkowski, M., and Zuccarello, F.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report a measurement of the energy spectrum of cosmic rays above $2.5{\times} 10^{18}$ eV based on $215,030$ events. New results are presented: at about $1.3{\times} 10^{19}$ eV, the spectral index changes from $2.51 \pm 0.03 \textrm{ (stat.)} \pm 0.05 \textrm{ (sys.)}$ to $3.05 \pm 0.05 \textrm{ (stat.)}\pm 0.10\textrm{ (sys.)}$, evolving to $5.1\pm0.3\textrm{ (stat.)} \pm 0.1\textrm{ (sys.)}$ beyond $5{\times} 10^{19}$ eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above $5{\times} 10^{18}$ eV is $(5.66 \pm 0.03 \textrm{ (stat.)} \pm 1.40 \textrm{ (sys.)} ) {\times} 10^{53}~$erg Mpc$^{-3}$., Comment: Published version; 2 figures, 1 table

Published
2020
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240. Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

Author

Consortium, The Cherenkov Telescope Array, Acharyya, A., Adam, R., Adams, C., Agudo, I., Aguirre-Santaella, A., Alfaro, R., Alfaro, J., Alispach, C., Aloisio, R., Batista, R. Alves, Amati, L., Ambrosi, G., Angüner, E. O., Antonelli, L. A., Aramo, C., Araudo, A., Armstrong, T., Arqueros, F., Asano, K., Ascasíbar, Y., Ashley, M., Balazs, C., Ballester, O., Larriva, A. Baquero, Martins, V. Barbosa, Barkov, M., de Almeida, U. Barres, Barrio, J. A., Bastieri, D., Becerra, J., Beck, G., Tjus, J. Becker, Benbow, W., Benito, M., Berge, D., Bernardini, E., Bernlöhr, K., Berti, A., Bertucci, B., Beshley, V., Biasuzzi, B., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Blazek, J., Bocchino, F., Boisson, C., Arbeletche, L. Bonneau, Bordas, P., Bosnjak, Z., Bottacini, E., Bozhilov, V., Bregeon, J., Brill, A., Bringmann, T., Brown, A. M., Brun, P., Brun, F., Bruno, P., Bulgarelli, A., Burton, M., Burtovoi, A., Buscemi, M., Cameron, R., Capasso, M., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Carosi, R., Carosi, A., Casanova, S., Cascone, E., Cassol, F., Catalani, F., Cauz, D., Cerruti, M., Chadwick, P., Chaty, S., Chen, A., Chernyakova, M., Chiaro, G., Chiavassa, A., Chikawa, M., Chudoba, J., Çolak, M., Conforti, V., Coniglione, R., Conte, F., Contreras, J. L., Coronado-Blazquez, J., Costa, A., Costantini, H., Cotter, G., Cristofari, P., D'Aì, A., D'Ammando, F., Damone, L. A., Daniel, M. K., Dazzi, F., De Angelis, A., De Caprio, V., Anjos, R. de Cássia dos, Pino, E. M. de Gouveia Dal, De Lotto, B., De Martino, D., Wilhelmi, E. de Oña, De Palma, F., de Souza, V., Delgado, C., Giler, A. G. Delgado, della Volpe, D., Depaoli, D., Di Girolamo, T., Di Pierro, F., Di Venere, L., Diebold, S., Dmytriiev, A., Domínguez, A., Donini, A., Doro, M., Ebr, J., Eckner, C., Edwards, T. D. P., Ekoume, T. R. N., Elsässer, D., Evoli, C., Falceta-Goncalves, D., Fedorova, E., Fegan, S., Feng, Q., Ferrand, G., Ferrara, G., Fiandrini, E., Fiasson, A., Filipovic, M., Fioretti, V., Fiori, M., Foffano, L., Fontaine, G., Fornieri, O., Franco, F. J., Fukami, S., Fukui, Y., Gaggero, D., Galaz, G., Gammaldi, V., Garcia, E., Garczarczyk, M., Gascon, D., Gent, A., Ghalumyan, A., Gianotti, F., Giarrusso, M., Giavitto, G., Giglietto, N., Giordano, F., Giuliani, A., Glicenstein, J., Gnatyk, R., Goldoni, P., González, M. M., Gourgouliatos, K., Granot, J., Grasso, D., Green, J., Grillo, A., Gueta, O., Gunji, S., Halim, A., Hassan, T., Heller, M., Cadena, S. Hernández, Hiroshima, N., Hnatyk, B., Hofmann, W., Holder, J., Horan, D., Hörandel, J., Horvath, P., Hovatta, T., Hrabovsky, M., Hrupec, D., Hughes, G., Humensky, T. B., Hütten, M., Iarlori, M., Inada, T., Inoue, S., Iocco, F., Iori, M., Jamrozy, M., Janecek, P., Jin, W., Jouvin, L., Jurysek, J., Karukes, E., Katarzyński, K., Kazanas, D., Kerszberg, D., Kherlakian, M. C., Kissmann, R., Knödlseder, J., Kobayashi, Y., Kohri, K., Komin, N., Kubo, H., Kushida, J., Lamanna, G., Lapington, J., Laporte, P., de Oliveira, M. A. Leigui, Lenain, J., Leone, F., Leto, G., Lindfors, E., Lohse, T., Lombardi, S., Longo, F., Lopez, A., López, M., López-Coto, R., Loporchio, S., Luque-Escamilla, P. L., Mach, E., Maggio, C., Maier, G., Mallamaci, M., de Almeida, R. Malta Nunes, Mandat, D., Manganaro, M., Mangano, S., Manicò, G., Marculewicz, M., Mariotti, M., Markoff, S., Marquez, P., Martí, J., Martinez, O., Martínez, M., Martínez, G., Martínez-Huerta, H., Maurin, G., Mazin, D., Mbarubucyeye, J. D., Miranda, D. Medina, Meyer, M., Miceli, M., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Mizuno, T., Mode, B., Moderski, R., Mohrmann, L., Molina, E., Montaruli, T., Moralejo, A., Morcuende-Parrilla, D., Morselli, A., Mukherjee, R., Mundell, C., Nagai, A., Nakamori, T., Nemmen, R., Niemiec, J., Nieto, D., Nikołajuk, M., Ninci, D., Noda, K., Nosek, D., Nozaki, S., Ohira, Y., Ohishi, M., Ohtani, Y., Oka, T., Okumura, A., Ong, R. A., Orienti, M., Orito, R., Orlandini, M., Orlando, S., Orlando, E., Ostrowski, M., Oya, I., Pagano, I., Pagliaro, A., Palatiello, M., Pantaleo, F. R., Paredes, J. M., Pareschi, G., Parmiggiani, N., Patricelli, B., Pavletić, L., Pe'er, A., Pecimotika, M., Pérez-Romero, J., Persic, M., Petruk, O., Pfrang, K., Piano, G., Piatteli, P., Pietropaolo, E., Pillera, R., Pilszyk, B., Pintore, F., Pohl, M., Poireau, V., Prado, R. R., Prandini, E., Prast, J., Principe, G., Prokoph, H., Prouza, M., Przybilski, H., Pühlhofer, G., Pumo, M. L., Queiroz, F., Quirrenbach, A., Rainò, S., Rando, R., Razzaque, S., Recchia, S., Reimer, O., Reisenegger, A., Renier, Y., Rhode, W., Ribeiro, D., Ribó, M., Richtler, T., Rico, J., Rieger, F., Rinchiuso, L., Rizi, V., Rodriguez, J., Fernandez, G. Rodriguez, Ramirez, J. C. Rodriguez, Rojas, G., Romano, P., Romeo, G., Rosado, J., Rowell, G., Rudak, B., Russo, F., Sadeh, I., Hatlen, E. Sæther, Safi-Harb, S., Greus, F. Salesa, Salina, G., Sanchez, D., Sánchez-Conde, M., Sangiorgi, P., Sano, H., Santander, M., Santos, E. M., Santos-Lima, R., Sanuy, A., Sarkar, S., Saturni, F. G., Sawangwit, U., Schussler, F., Schwanke, U., Sciacca, E., Scuderi, S., Seglar-Arroyo, M., Sergijenko, O., Servillat, M., Seweryn, K., Shalchi, A., Sharma, P., Shellard, R. C., Siejkowski, H., Silk, J., Siqueira, C., Sliusar, V., Słowikowska, A., Sokolenko, A., Sol, H., Spencer, S., Stamerra, A., Stanič, S., Starling, R., Stolarczyk, T., Straumann, U., Strišković, J., Suda, Y., Suomijarvi, T., Świerk, P., Tavecchio, F., Taylor, L., Tejedor, L. A., Teshima, M., Testa, V., Tibaldo, L., Peixoto, C. J. Todero, Tokanai, F., Tonev, D., Tosti, G., Tosti, L., Tothill, N., Truzzi, S., Travnicek, P., Vagelli, V., Vallage, B., Vallania, P., van Eldik, C., Vandenbroucke, J., Varner, G. S., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Ventura, S., Vercellone, S., Vergani, S., Verna, G., Viana, A., Vigorito, C. F., Vink, J., Vitale, V., Vorobiov, S., Vovk, I., Vuillaume, T., Wagner, S. J., Walter, R., Watson, J., Weniger, C., White, R., White, M., Wiemann, R., Wierzcholska, A., Will, M., Williams, D. A., Wischnewski, R., Yanagita, S., Yang, L., Yoshikoshi, T., Zacharias, M., Zaharijas, G., Zakaria, A. A., Zampieri, L., Zanin, R., Zaric, D., Zavrtanik, M., Zavrtanik, D., Zdziarski, A. A., Zech, A., Zechlin, H., Zhdanov, V. I., and Živec, M.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Abstract

We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies. "Full likelihood tables complementing our analysis are provided here [ https://doi.org/10.5281/zenodo.4057987 ]", Comment: 68 pages (including references) and 26 figures; text identical to the version published in JCAP

Published
2020
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241. Reconstruction of Events Recorded with the Surface Detector of the Pierre Auger Observatory

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Castillo, J. Alvarez, Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Billoir, P., Bister, T., Biteau, J., Blanco, A., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Bridgeman, A., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Calcagni, L., Cancio, A., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Dhital, N., Di Matteo, A., Castro, M. L. Díaz, Dobrigkeit, C., D'Olivo, J. C., Dorosti, Q., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Halliday, R., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Mezek, G. Kukec, Lago, B. L., LaHurd, D., Lang, R. G., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lorek, R., Luce, Q., Lucero, A., Payeras, A. Machado, Malacari, M., Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mockler, D., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Panetta, M. P., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Peters, C., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Schulz, A., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Elipe, G. Torralba, Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Urban, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valiño, I., Valore, L., van Vliet, A., Varela, E., Cárdenas, B. Vargas, Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Villaseñor, L., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., Ziolkowski, M., and Zuccarello, F.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract

Cosmic rays arriving at Earth collide with the upper parts of the atmosphere, thereby inducing extensive air showers. When secondary particles from the cascade arrive at the ground, they are measured by surface detector arrays. We describe the methods applied to the measurements of the surface detector of the Pierre Auger Observatory to reconstruct events with zenith angles less than $60^\circ$ using the timing and signal information recorded using the water-Cherenkov detector stations. In addition, we assess the accuracy of these methods in reconstructing the arrival directions of the primary cosmic ray particles and the sizes of the induced showers., Comment: Published version, 36 pages, 14 figures

Published
2020
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242. Studies on the response of a water-Cherenkov detector of the Pierre Auger Observatory to atmospheric muons using an RPC hodoscope

Author

The Pierre Auger Collaboration, Aab, A., Abreu, P., Aglietta, M., Albury, J. M., Allekotte, I., Almela, A., Castillo, J. Alvarez, Alvarez-Muñiz, J., Batista, R. Alves, Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P. R. Araújo, Asorey, H., Assis, P., Avila, G., Badescu, A. M., Bakalova, A., Balaceanu, A., Barbato, F., Luz, R. J. Barreira, Becker, K. H., Bellido, J. A., Berat, C., Bertaina, M. E., Bertou, X., Biermann, P. L., Bister, T., Biteau, J., Blanco, A., Blazek, J., Bleve, C., Boháčová, M., Boncioli, D., Bonifazi, C., Arbeletche, L. Bonneau, Borodai, N., Botti, A. M., Brack, J., Bretz, T., Briechle, F. L., Buchholz, P., Bueno, A., Buitink, S., Buscemi, M., Caballero-Mora, K. S., Caccianiga, L., Calcagni, L., Cancio, A., Canfora, F., Caracas, I., Carceller, J. M., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Chinellato, J. A., Choi, K., Chudoba, J., Chytka, L., Clay, R. W., Cerutti, A. C. Cobos, Colalillo, R., Coleman, A., Coluccia, M. R., Conceição, R., Condorelli, A., Consolati, G., Contreras, F., Convenga, F., Covault, C. E., Dasso, S., Daumiller, K., Dawson, B. R., Day, J. A., de Almeida, R. M., de Jesús, J., de Jong, S. J., De Mauro, G., Neto, J. R. T. de Mello, De Mitri, I., de Oliveira, J., Franco, D. de Oliveira, de Souza, V., De Vito, E., Debatin, J., del Río, M., Deligny, O., Dhital, N., Di Matteo, A., Castro, M. L. Díaz, Dobrigkeit, C., D'Olivo, J. C., Dorosti, Q., Anjos, R. C. dos, Dova, M. T., Ebr, J., Engel, R., Epicoco, I., Erdmann, M., Escobar, C. O., Etchegoyen, A., Falcke, H., Farmer, J., Farrar, G., Fauth, A. C., Fazzini, N., Feldbusch, F., Fenu, F., Fick, B., Figueira, J. M., Filipčič, A., Fodran, T., Freire, M. M., Fujii, T., Fuster, A., Galea, C., Galelli, C., García, B., Vegas, A. L. Garcia, Gemmeke, H., Gesualdi, F., Gherghel-Lascu, A., Ghia, P. L., Giaccari, U., Giammarchi, M., Giller, M., Glombitza, J., Gobbi, F., Gollan, F., Golup, G., Berisso, M. Gómez, Vitale, P. F. Gómez, Gongora, J. P., González, N., Goos, I., Góra, D., Gorgi, A., Gottowik, M., Grubb, T. D., Guarino, F., Guedes, G. P., Guido, E., Hahn, S., Halliday, R., Hampel, M. R., Hansen, P., Harari, D., Harvey, V. M., Haungs, A., Hebbeker, T., Heck, D., Hill, G. C., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, M., Huege, T., Hulsman, J., Insolia, A., Isar, P. G., Johnsen, J. A., Jurysek, J., Kääpä, A., Kampert, K. H., Keilhauer, B., Kemp, J., Klages, H. O., Kleifges, M., Kleinfeller, J., Köpke, M., Mezek, G. Kukec, Lago, B. L., LaHurd, D., Lang, R. G., de Oliveira, M. A. Leigui, Lenok, V., Letessier-Selvon, A., Lhenry-Yvon, I., Presti, D. Lo, Lopes, L., López, R., Lorek, R., Luce, Q., Lucero, A., Payeras, A. Machado, Malacari, M., Mancarella, G., Mandat, D., Manning, B. C., Manshanden, J., Mantsch, P., Marafico, S., Mariazzi, A. G., Mariş, I. C., Marsella, G., Martello, D., Martinez, H., Bravo, O. Martínez, Mastrodicasa, M., Mathes, H. J., Matthews, J., Matthiae, G., Mayotte, E., Mazur, P. O., Medina-Tanco, G., Melo, D., Menshikov, A., Merenda, K. -D., Michal, S., Micheletti, M. I., Miramonti, L., Mockler, D., Mollerach, S., Montanet, F., Morello, C., Mostafá, M., Müller, A. L., Muller, M. A., Mulrey, K., Mussa, R., Muzio, M., Namasaka, W. M., Nellen, L., Niculescu-Oglinzanu, M., Niechciol, M., Nitz, D., Nosek, D., Novotny, V., Nožka, L., Nucita, A, Núñez, L. A., Palatka, M., Pallotta, J., Panetta, M. P., Papenbreer, P., Parente, G., Parra, A., Pech, M., Pedreira, F., Pękala, J., Pelayo, R., Peña-Rodriguez, J., Armand, J. Perez, Perlin, M., Perrone, L., Peters, C., Petrera, S., Pierog, T., Pimenta, M., Pirronello, V., Platino, M., Pont, B., Pothast, M., Privitera, P., Prouza, M., Puyleart, A., Querchfeld, S., Rautenberg, J., Ravignani, D., Reininghaus, M., Ridky, J., Riehn, F., Risse, M., Ristori, P., Rizi, V., de Carvalho, W. Rodrigues, Rojo, J. Rodriguez, Roncoroni, M. J., Roth, M., Roulet, E., Rovero, A. C., Ruehl, P., Saffi, S. J., Saftoiu, A., Salamida, F., Salazar, H., Salina, G., Gomez, J. D. Sanabria, Sánchez, F., Santos, E. M., Santos, E., Sarazin, F., Sarmento, R., Sarmiento-Cano, C., Sato, R., Savina, P., Schäfer, C., Scherini, V., Schieler, H., Schimassek, M., Schimp, M., Schlüter, F., Schmidt, D., Scholten, O., Schovánek, P., Schröder, F. G., Schröder, S., Sciutto, S. J., Scornavacche, M., Shellard, R. C., Sigl, G., Silli, G., Sima, O., Šmída, R., Sommers, P., Soriano, J. F., Souchard, J., Squartini, R., Stadelmaier, M., Stanca, D., Stanič, S., Stasielak, J., Stassi, P., Streich, A., Suárez-Durán, M., Sudholz, T., Suomijärvi, T., Supanitsky, A. D., Šupík, J., Szadkowski, Z., Taboada, A., Tapia, A., Timmermans, C., Tkachenko, O., Tobiska, P., Peixoto, C. J. Todero, Tomé, B., Elipe, G. Torralba, Travaini, A., Travnicek, P., Trimarelli, C., Trini, M., Tueros, M., Ulrich, R., Unger, M., Urban, M., Vaclavek, L., Vacula, M., Galicia, J. F. Valdés, Valiño, I., Valore, L., van Vliet, A., Varela, E., Cárdenas, B. Vargas, Vásquez-Ramírez, A., Veberič, D., Ventura, C., Quispe, I. D. Vergara, Verzi, V., Vicha, J., Villaseñor, L., Vink, J., Vorobiov, S., Wahlberg, H., Watson, A. A., Weber, M., Weindl, A., Wiencke, L., Wilczyński, H., Winchen, T., Wirtz, M., Wittkowski, D., Wundheiler, B., Yushkov, A., Zapparrata, O., Zas, E., Zavrtanik, D., Zavrtanik, M., Zehrer, L., Zepeda, A., Ziolkowski, M., and Zuccarello, F.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract

Extensive air showers, originating from ultra-high energy cosmic rays, have been successfully measured through the use of arrays of water-Cherenkov detectors (WCDs). Sophisticated analyses exploiting WCD data have made it possible to demonstrate that shower simulations, based on different hadronic-interaction models, cannot reproduce the observed number of muons at the ground. The accurate knowledge of the WCD response to muons is paramount in establishing the exact level of this discrepancy. In this work, we report on a study of the response of a WCD of the Pierre Auger Observatory to atmospheric muons performed with a hodoscope made of resistive plate chambers (RPCs), enabling us to select and reconstruct nearly 600 thousand single muon trajectories with zenith angles ranging from 0$^\circ$ to 55$^\circ$. Comparison of distributions of key observables between the hodoscope data and the predictions of dedicated simulations allows us to demonstrate the accuracy of the latter at a level of 2%. As the WCD calibration is based on its response to atmospheric muons, the hodoscope data are also exploited to show the long-term stability of the procedure., Comment: Published version, 25 pages, 9 figures

Published
2020
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243. Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 {\AA} line

Author

Pietrow, A. G. M., Kiselman, D., Rodríguez, J. de la Cruz, Baso, C. J. Díaz, Yabar, A. Pastor, and Yadav, R.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

It has so far proven impossible to reproduce all aspects of the solar plage chromosphere in quasi-realistic numerical models. The magnetic field configuration in the lower atmosphere is one of the few free parameters in such simulations. The literature only offers proxy-based estimates of the field strength, as it is difficult to obtain observational constraints in this region. Sufficiently sensitive spectro-polarimetric measurements require a high signal-to-noise ratio, spectral resolution, and cadence, which are at the limit of current capabilities. We use critically sampled spectro-polarimetric observations of the \cair line obtained with the CRISP instrument of the Swedish 1-m Solar Telescope to study the strength and inclination of the chromospheric magnetic field of a plage region. This will provide direct physics-based estimates of these values, which could aid modelers to put constraints on plage models. We increased the signal-to-noise ratio of the data by applying several methods including deep learning and PCA. We estimated the noise level to be $1\cdot10^{-3} I_c$. We then used STiC, a non-local thermodynamic equilibrium (NLTE) inversion code to infer the atmospheric structure and magnetic field pixel by pixel. We are able to infer the magnetic field strength and inclination for a plage region and for fibrils in the surrounding canopy. In the plage we report an absolute field strength of $|B| =440 \pm 90$ G, with an inclination of $10^\circ \pm 16^\circ$ with respect to the local vertical. This value for $|B|$ is roughly double of what was reported previously, while the inclination matches previous studies done in the photosphere. In the fibrillar region we found $|B| = 300 \pm 50$ G, with an inclination of $50^\circ \pm 13^\circ$., Comment: Accepted September 22th

Published
2020
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244. Stratification of canopy magnetic fields in a plage region. Constraints from a spatially-regularized weak-field approximation method

Author

Morosin, R., Rodriguez, J. de la Cruz, Vissers, G. J. M., and Yadav, R.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The role of magnetic fields in the chromospheric heating problem remains greatly unconstrained. Most theoretical predictions from numerical models rely on a magnetic configuration, field strength and connectivity whose details have not been well established with observational studies. High-resolution studies of chromospheric magnetic fields in plage are very scarce or non-existent in general. Our aim is to study the stratification of the magnetic field vector in plage regions. We use high-spatial resolution full-Stokes observations acquired with CRISP instrument at the Swedish 1-m Solar Telescope in the Mg I $\lambda$5173, Na I $\lambda$5896 and Ca II $\lambda$8542 lines. We have developed a spatially-regularized weak-field approximation (WFA) method based on the idea of spatial regularization. This method allows for a fast computation of magnetic field maps for an extended field of view. The fidelity of this new technique has been assessed using a snapshot from a realistic 3D magnetohydrodynamics simulation. We have derived the depth-stratification of the line-of-sight component of the magnetic field from the photosphere to the chromosphere in a plage region. The magnetic fields are concentrated in the intergranular lanes in the photosphere and expand horizontally toward the chromosphere, filling all the space and forming a canopy. Our results suggest that the lower boundary of this canopy must be located around 400-600 km from the photosphere. The mean canopy total magnetic field strength in the lower chromosphere ($z\approx760$ km) is 658 G. At $z=1160$ km we estimate $\approx 417$ G. We propose a modification to the WFA that improves its applicability to data with worse signal-to-noise ratio. These methods provide a quick and reliable way of studying multi-layer magnetic field observations without the many difficulties inherent to other inversion methods., Comment: Accepted for publication on 2020-08-27

Published
2020
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245. ALMA observations of transient heating in a solar active region

Author

Santos, J. M. da Silva, Rodríguez, J. de la Cruz, White, S. M., Leenaarts, J., Vissers, G. J. M., and Hansteen, V. H.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We aim to investigate the temperature enhancements and formation heights of impulsive heating phenomena in solar active-regions such as Ellerman bombs (EBs), ultraviolet bursts (UVBs), and flaring active-region fibrils (FAFs) using interferometric observations in the millimeter (mm) continuum provided by the Atacama Large Millimeter/submillimeter Array (ALMA). We examined 3 mm signatures of heating events identified in Solar Dynamics Observatory (SDO) observations of an active region and compared the results with synthetic spectra from a 3D radiative magnetohydrodynamic simulation. We estimated the contribution from the corona to the mm brightness using differential emission measure analysis. We report the null detection of EBs in the 3 mm continuum at $\sim1.2$" spatial resolution, which is evidence that they are sub-canopy events that do not significantly contribute to heating the upper chromosphere. In contrast, we find the active region to be populated with multiple compact, bright, flickering mm bursts -- reminiscent of UVBs. The high brightness temperatures of up to $\sim14200$ K in some events have a significant contribution (up to $\sim$7%) from the corona. We also detect FAF-like events in the 3 mm continuum that show rapid motions of $>10000\,$K plasma launched with high plane-of-sky velocities ($37-340\rm\,km\,s^{-1}$) from bright kernels. The mm FAFs are the brightest class of warm canopy fibrils that connect magnetic regions of opposite polarities. The simulation confirms that ALMA should be able to detect the mm counterparts of UVBs and small flares and thus provide a complementary diagnostic for localized heating in the solar chromosphere., Comment: revised; accepted in Astronomy & Astrophysics

Published
2020
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246. Quantum-Critical Spin-Density Waves in Iron-Selenide High-Tc Superconductors

Author

Rodriguez, J. P.

Subjects
Condensed Matter - Superconductivity
Abstract

Hidden spin-density waves (hSDW) with Neel ordering vector (pi,pi) have been proposed recently as parent groundstates to electron-doped iron-selenide superconductors. Doping such groundstates can result in visible electron-type Fermi surface pockets and faint hole-type Fermi surface pockets at the corner of the folded Brillouin zone. A Cooper pair instability that alternates in sign between the electron-type and the hole-type Fermi surfaces has recently been predicted. The previous is due to the interaction of electrons and holes with hidden spin fluctuations connected with hSDW order that is near a quantum-critical point. Quantum criticality is tuned in by increasing the strength of Hund's Rule from the hSDW state. We find that the exchange of hidden spin fluctuations by electrons/holes in the critical hSDW state results in asymptotic freedom. In particular, the strength of spin-flip interactions becomes weaker and weaker on length scales that are shorter and shorter compared to the range of hSDW order. We then argue that string states that connect well-separated particle/hole excitations in the hSDW are robust. This suggests a picture where the hole degrees of freedom mentioned previously are confined., Comment: 19 pages, 6 figures

Published
2020

247. COVIDGR dataset and COVID-SDNet methodology for predicting COVID-19 based on Chest X-Ray images

Author

Tabik, S., Gómez-Ríos, A., Martín-Rodríguez, J. L., Sevillano-García, I., Rey-Area, M., Charte, D., Guirado, E., Suárez, J. L., Luengo, J., Valero-González, M. A., García-Villanova, P., Olmedo-Sánchez, E., and Herrera, F.

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Computer Science - Computer Vision and Pattern Recognition
Abstract

Currently, Coronavirus disease (COVID-19), one of the most infectious diseases in the 21st century, is diagnosed using RT-PCR testing, CT scans and/or Chest X-Ray (CXR) images. CT (Computed Tomography) scanners and RT-PCR testing are not available in most medical centers and hence in many cases CXR images become the most time/cost effective tool for assisting clinicians in making decisions. Deep learning neural networks have a great potential for building COVID-19 triage systems and detecting COVID-19 patients, especially patients with low severity. Unfortunately, current databases do not allow building such systems as they are highly heterogeneous and biased towards severe cases. This paper is three-fold: (i) we demystify the high sensitivities achieved by most recent COVID-19 classification models, (ii) under a close collaboration with Hospital Universitario Cl\'inico San Cecilio, Granada, Spain, we built COVIDGR-1.0, a homogeneous and balanced database that includes all levels of severity, from normal with Positive RT-PCR, Mild, Moderate to Severe. COVIDGR-1.0 contains 426 positive and 426 negative PA (PosteroAnterior) CXR views and (iii) we propose COVID Smart Data based Network (COVID-SDNet) methodology for improving the generalization capacity of COVID-classification models. Our approach reaches good and stable results with an accuracy of $97.72\% \pm 0.95 \%$, $86.90\% \pm 3.20\%$, $61.80\% \pm 5.49\%$ in severe, moderate and mild COVID-19 severity levels (Paper accepted for publication in Journal of Biomedical and Health Informatics). Our approach could help in the early detection of COVID-19. COVIDGR-1.0 along with the severity level labels are available to the scientific community through this link https://dasci.es/es/transferencia/open-data/covidgr/., Comment: Paper accepted in Journal of Biomedical And Health Informatics

Published
2020

248. High-resolution observations of the solar photosphere, chromosphere and transition region. A database of coordinated IRIS and SST observations

Author

van der Voort, L. H. M. Rouppe, De Pontieu, B., Carlsson, M., Rodriguez, J. de la Cruz, Bose, S., Chintzoglou, G., Drews, A., Froment, C., Gosic, M., Graham, D. R., Hansteen, V. H., Henriques, V. M. J., Jafarzadeh, S., Joshi, J., Kleint, L., Kohutova, P., Leifsen, T., Martinez-Sykora, J., Nobrega-Siverio, D., Ortiz, A., Pereira, T. M. D., Popovas, A., Noda, C. Quintero, Dalda, A. Sainz, Scharmer, G. B., Schmit, D., Scullion, E., Skogsrud, H., Szydlarski, M., Timmons, R., Vissers, G. J. M., Woods, M. M., and Zacharias, P.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

NASA's Interface Region Imaging Spectrograph (IRIS) provides high resolution observations of the solar atmosphere through UV spectroscopy and imaging. Since the launch of IRIS in June 2013, we have conducted systematic observation campaigns in coordination with the Swedish 1-m Solar Telescope (SST) on La Palma. The SST provides complementary high-resolution observations of the photosphere and chromosphere. The SST observations include spectro-polarimetric imaging in photospheric Fe I lines and spectrally-resolved imaging in the chromospheric Ca II 8542 A, H-alpha, and Ca II K lines. We present a database of co-aligned IRIS and SST datasets that is open for analysis to the scientific community. The database covers a variety of targets including active regions, sunspots, plage, quiet Sun, and coronal holes., Comment: Accepted for publication in Astronomy & Astrophysics (July 21, 2020)

Published
2020
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249. Quantum confinement of Dirac quasiparticles in graphene patterned with subnanometer precision

Author

Río, E. Cortés-del, Mallet, P., González-Herrero, H., Lado, J. L., Fernández-Rossier, J., Gómez-Rodríguez, J. M., Veuillen, J-Y., and Brihuega, I.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Quantum confinement of graphene Dirac-like electrons in artificially crafted nanometer structures is a long sought goal that would provide a strategy to selectively tune the electronic properties of graphene, including bandgap opening or quantization of energy levels However, creating confining structures with nanometer precision in shape, size and location, remains as an experimental challenge, both for top-down and bottom-up approaches. Moreover, Klein tunneling, offering an escape route to graphene electrons, limits the efficiency of electrostatic confinement. Here, a scanning tunneling microscope (STM) is used to create graphene nanopatterns, with sub-nanometer precision, by the collective manipulation of a large number of H atoms. Individual graphene nanostructures are built at selected locations, with predetermined orientations and shapes, and with dimensions going all the way from 2 nanometers up to 1 micron. The method permits to erase and rebuild the patterns at will, and it can be implemented on different graphene substrates. STM experiments demonstrate that such graphene nanostructures confine very efficiently graphene Dirac quasiparticles, both in zero and one dimensional structures. In graphene quantum dots, perfectly defined energy band gaps up to 0.8 eV are found, that scale as the inverse of the dots linear dimension, as expected for massless Dirac fermions, Comment: Main Manuscript and Supporting Information

Published
2020
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250. A unified accretion-ejection paradigm for black hole X-ray binaries. V. Low-frequency quasi-periodic oscillations

Author

Marcel, G., Cangemi, F., Rodriguez, J., Neilsen, J., Ferreira, J., Petrucci, P. -O., Malzac, J., Barnier, S., and Clavel, M.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We proposed that the spectral evolution of transient X-ray binaries (XrB) is due to an interplay between two flows: a standard accretion disk (SAD) in the outer parts and a jet-emitting disk (JED) in the inner parts. We showed in previous papers that the spectral evolution in X-ray and radio during the 2010-2011 outburst of GX339-4 can be recovered. We now investigate the presence of low frequency quasi-periodic oscillations (LFQPOs) during an X-ray outburst, and address the possible correlation between the frequencies of these LFQPOs and the transition radius between the two flows, rJ. We select X-ray and radio data form 3 outbursts of GX339-4. We use the method detailed in paper IV to obtain $r_J(t)$ and $\dot{m}_{in}(t)$ for each outburst to reproduce the correlated evolution of the X-ray spectra and the radio emission for 3 different activity cycles of GX339-4. We also independently search and report the detection of 7 new LFQPOs in addition to the literature. We show that the frequency of Type C QPOs can be linked to the dynamical JED-SAD transition radius rJ, rather than the radius of optically thin-thick transition. The scaling factor q such that $\nu_{QPO} \simeq \nu_K (r_J) / q$ is $q \simeq 70-140$, consistent during the 4 cycles and similar to previous studies. The JED-SAD hybrid disk configuration not only provides a successful paradigm allowing us to describe XrB cycles, but also matches the QPO frequencies evolution. QPOs provide an indirect way to probe the JED-SAD transition radius, where an undetermined process produces secular variability. The demonstrated relation between the transition radius links Type C QPOs to the transition between the two flows, tying it to the inner magnetized structure of the jets. This direct connection between the jets' structure and the process responsible for Type C QPOs could naturally explain their puzzling multi-wavelength behavior., Comment: Accepted in publication in A&A, replaced since language editing

Published
2020
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