Volume 670, February 2023
|Number of page(s)||20|
|Section||Interstellar and circumstellar matter|
|Published online||30 January 2023|
Study of the GeV to TeV morphology of the γ Cygni SNR (G 78.2+2.1) with MAGIC and Fermi-LAT
Evidence for cosmic ray escape
Inst. de Astrofísica de Canarias,
E-38200 La Laguna, and Universidad de La Laguna, Dpto. Astrofísica,
La Laguna, Tenerife, Spain
2 Università di Udine, and INFN Trieste, 33100 Udine, Italy
3 National Institute for Astrophysics (INAF), 00136 Rome, Italy
4 ETH Zurich, CH-8093 Zurich, Switzerland
5 Technische Universität Dortmund, D-44221 Dortmund, Germany
6 Croatian Consortium: University of Rijeka, Department of Physics, 51000 Rijeka ; University of Split – FESB, 21000 Split ; University of Zagreb – FER, 10000 Zagreb ; University of Osijek, 31000 Osijek ; Rudjer Boskovic Institute, 10000 Zagreb, Croatia
7 Saha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Salt Lake, Sector-1, Kolkata 700064, India
8 Centro Brasileiro de Pesquisas Físicas (CBPF), 22290-180 URCA, Rio de Janeiro (RJ), Brasil
9 IPARCOS Institute and EMFTEL Department, Universidad Complutense de Madrid, 28040 Madrid, Spain
10 University of Lodz, Faculty of Physics and Applied Informatics, Department of Astrophysics, 90-236 Lodz, Poland
11 Università di Siena and INFN Pisa, 53100 Siena, Italy
12 Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
13 Istituto Nazionale Fisica Nucleare (INFN), 00044 Frascati (Roma), Italy
14 Max-Planck-Institut für Physik, 80805 München, Germany
15 Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), Spain
16 Università di Padova and INFN, 35131 Padova, Italy
17 Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
18 Universitat de Barcelona, ICCUB, IEEC-UB, 08028 Barcelona, Spain
19 The Armenian Consortium: ICRANet-Armenia at NAS RA, A. Alikhanyan National Laboratory, Republic of Armenia
20 Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, E-28040 Madrid, Spain
21 Universität Würzburg, 97074 Würzburg, Germany
22 Finnish MAGIC Consortium: Finnish Centre of Astronomy with ESO (FINCA), University of Turku, 20014 Turku ; Astronomy Research Unit, University of Oulu, 90014 Oulu, Finland
23 Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
24 Japanese MAGIC Consortium: ICRR, The University of Tokyo, 277-8582 Chiba ; Department of Physics, Kyoto University, 606-8502 Kyoto ; Tokai University, 259-1292 Kanagawa ; RIKEN, 351-0198 Saitama, Japan
25 Inst. for Nucl. Research and Nucl. Energy, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
26 Sapienza Università di Roma and INFN Roma, 00185 Rome, Italy
27 INAF, Osservatorio Astrofisico di Arcetri, 50125 Firenze, Italy
28 Institute for Astro- and Particle Physics, University of Innsbruck, A-6020 Innsbruck, Austria
29 Port d’Informació Científica (PIC) E-08193 Bellaterra (Barcelona), Spain
30 Dipartimento di Fisica, Università di Trieste, 34127 Trieste, Italy
31 INAF-Trieste and Dept. of Physics & Astronomy, University of Bologna, Italy
Accepted: 13 October 2020
Context. Diffusive shock acceleration (DSA) is the most promising mechanism that accelerates Galactic cosmic rays (CRs) in the shocks of supernova remnants (SNRs). It is based on particles scattering caused by turbulence ahead and behind the shock. The turbulence upstream is supposedly generated by the CRs, but this process is not well understood. The dominant mechanism may depend on the evolutionary state of the shock and can be studied via the CRs escaping upstream into the interstellar medium (ISM).
Aims. Previous observations of the γ Cygni SNR showed a difference in morphology between GeV and TeV energies. Since this SNR has the right age and is at the evolutionary stage for a significant fraction of CRs to escape, our aim is to understand γ-ray emission in the vicinity of the γ Cygni SNR.
Methods. We observed the region of the γ Cygni SNR with the MAGIC Imaging Atmospheric Cherenkov telescopes between 2015 May and 2017 September recording 87 h of good-quality data. Additionally, we analysed Fermi-LAT data to study the energy dependence of the morphology as well as the energy spectrum in the GeV to TeV range. The energy spectra and morphology were compared against theoretical predictions, which include a detailed derivation of the CR escape process and their γ-ray generation.
Results. The MAGIC and Fermi-LAT data allowed us to identify three emission regions that can be associated with the SNR and that dominate at different energies. Our hadronic emission model accounts well for the morphology and energy spectrum of all source components. It constrains the time-dependence of the maximum energy of the CRs at the shock, the time-dependence of the level of turbulence, and the diffusion coefficient immediately outside the SNR shock. While in agreement with the standard picture of DSA, the time-dependence of the maximum energy was found to be steeper than predicted, and the level of turbulence was found to change over the lifetime of the SNR.
Key words: acceleration of particles / cosmic rays / gamma rays: general / gamma rays: ISM / ISM: clouds / ISM: supernova remnants
© ESO 2023
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.