Gamma-ray astronomy

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Time-resolved hadronic particle acceleration in the recurrent nova RS Ophiuchi.

Science (New York, N.Y.) 376:6588 (2022) 77-80

Authors:

H.E.S.S. Collaboration*†, F Aharonian, F Ait Benkhali, EO Angüner, H Ashkar, M Backes, V Baghmanyan, V Barbosa Martins, R Batzofin, Y Becherini, D Berge, K Bernlöhr, B Bi, M Böttcher, C Boisson, J Bolmont, M de Bony de Lavergne, M Breuhaus, R Brose, F Brun, S Caroff, S Casanova, M Cerruti, T Chand, A Chen, G Cotter, J Damascene Mbarubucyeye, A Djannati-Ataï, A Dmytriiev, V Doroshenko, C Duffy, K Egberts, J-P Ernenwein, S Fegan, K Feijen, A Fiasson, G Fichet de Clairfontaine, G Fontaine, M Füßling, S Funk, S Gabici, YA Gallant, S Ghafourizadeh, G Giavitto, L Giunti, D Glawion, JF Glicenstein, M-H Grondin, G Hermann, JA Hinton, M Hörbe, W Hofmann, C Hoischen, TL Holch, M Holler, D Horns, Zhiqiu Huang, M Jamrozy, F Jankowsky, I Jung-Richardt, E Kasai, K Katarzyński, U Katz, D Khangulyan, B Khélifi, S Klepser, W Kluźniak, Nu Komin, R Konno, K Kosack, D Kostunin, S Le Stum, A Lemière, M Lemoine-Goumard, J-P Lenain, F Leuschner, T Lohse, A Luashvili, I Lypova, J Mackey, D Malyshev, D Malyshev, V Marandon, P Marchegiani, A Marcowith, G Martí-Devesa, R Marx, G Maurin, M Meyer, A Mitchell, R Moderski, L Mohrmann, A Montanari, E Moulin, J Muller, T Murach, K Nakashima, M de Naurois, A Nayerhoda, J Niemiec, A Priyana Noel, P O'Brien, S Ohm, L Olivera-Nieto, E de Ona Wilhelmi, M Ostrowski, S Panny, M Panter, RD Parsons, G Peron, S Pita, V Poireau, DA Prokhorov, H Prokoph, G Pühlhofer, M Punch, A Quirrenbach, P Reichherzer, A Reimer, O Reimer, M Renaud, B Reville, F Rieger, G Rowell, B Rudak, H Rueda Ricarte, E Ruiz-Velasco, V Sahakian, S Sailer, H Salzmann, DA Sanchez, A Santangelo, M Sasaki, J Schäfer, F Schüssler, HM Schutte, U Schwanke, M Senniappan, JNS Shapopi, R Simoni, A Sinha, H Sol, A Specovius, S Spencer, Ł Stawarz, S Steinmassl, C Steppa, T Takahashi, T Tanaka, AM Taylor, R Terrier, C Thorpe-Morgan, M Tsirou, N Tsuji, R Tuffs, Y Uchiyama, T Unbehaun, C van Eldik, B van Soelen, J Veh, C Venter, J Vink, SJ Wagner, F Werner, R White, A Wierzcholska, Yu Wun Wong, A Yusafzai, M Zacharias, D Zargaryan, AA Zdziarski, A Zech, SJ Zhu, S Zouari, N Żywucka

Abstract:

Recurrent novae are repeating thermonuclear explosions in the outer layers of white dwarfs, due to the accretion of fresh material from a binary companion. The shock generated when ejected material slams into the companion star's wind can accelerate particles. We report very-high-energy (VHE; [Formula: see text]) gamma rays from the recurrent nova RS Ophiuchi, up to 1 month after its 2021 outburst, observed using the High Energy Stereoscopic System (H.E.S.S.). The temporal profile of VHE emission is similar to that of lower-energy giga-electron volt emission, indicating a common origin, with a 2-day delay in peak flux. These observations constrain models of time-dependent particle energization, favoring a hadronic emission scenario over the leptonic alternative. Shocks in dense winds provide favorable environments for efficient acceleration of cosmic rays to very high energies.
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Search and identification of transient and variable radio sources using MeerKAT observations: a case study on the MAXI J1820+070 field

(2022)

Authors:

A Rowlinson, J Meijn, J Bright, AJ van der Horst, S Chastain, S Fijma, R Fender, I Heywood, RAMJ Wijers, PA Woudt, A Andersson, GR Sivakoff, E Tremou, LN Driessen
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21 new long-term variables in the GX 339-4 field: two years of MeerKAT monitoring

(2022)

Authors:

LN Driessen, BW Stappers, E Tremou, RP Fender, PA Woudt, R Armstrong, S Bloemen, P Groot, I Heywood, A Horesh, AJ van der Horst, E Koerding, VA McBride, JCA Miller-Jones, KP Mooley, A Rowlinson, RAMJ Wijers
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Active Galactic Nuclei population studies with the Cherenkov Telescope Array

Proceedings of Science 395 (2022)

Authors:

H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, T Armstrong, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, L Baroncelli, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck, J Becker Tjus, W Bednarek, A Belfiore, L Bellizzi, R Belmont, W Benbow, D Berge, E Bernardini, MI Bernardos, K Bernlöhr, A Berti

Abstract:

The Cherenkov Telescope Array (CTA) observatory is the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Building on the strengths of current IACTs, CTA is designed to achieve an order of magnitude improvement in sensitivity, with unprecedented angular and energy resolution. CTA will also increase the energy reach of IACTs, observing photons in the energy range from 20 GeV to beyond 100 TeV. These advances in performance will see CTA heralding in a new era for high-energy astrophysics, with the emphasis shifting from source discovery, to population studies and precision measurements. In this talk we discuss CTA’s ability to conduct source population studies of γ-ray bright active galactic nuclei and how this ability will enhance our understanding on the redshift evolution of this dominant γ-ray source class.

Detection methods for the Cherenkov Telescope Array at very-short exposure times

Proceedings of Science 395 (2022)

Authors:

A Di Piano, A Bulgarelli, V Fioretti, L Baroncelli, N Parmiggiani, F Longo, A Stamerra, A López-Oramas, G Stratta, G De Cesare, H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, T Armstrong, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck, J Becker Tjus, W Bednarek

Abstract:

The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for very-high-energy (VHE) gamma-ray astronomy, with the deployment of tens of highly sensitive and fast-reacting Cherenkov telescopes. It will cover a wide energy range (20 GeV - 300 TeV) with unprecedented sensitivity. To maximize the scientific return, the observatory will be provided with an online software system that will perform the first analysis of scientific data in real-time. This study investigates the precision and accuracy of available science tools and analysis techniques for the short-term detection of gamma-ray sources, in terms of sky localization, detection significance and, if significant detection is achieved, a first estimation of the integral photon flux. The scope is to evaluate the feasibility of the algorithms' implementation in the real-time analysis of CTA. In this contribution we present a general overview of the methods and some of the results for the test case of the short-term detection of a gamma-ray burst afterglow, as the VHE counterpart of a gravitational wave event.