Refereed journal article or data article (A1)
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
List of Authors: Acciari VA, Ansoldi S, Antonelli LA, Engels AA, Baack D, Babic A, Banerjee B, de Almeida UB, Barrio JA, Gonzalez JB, Bednarek W, Bellizzi L, Bernardini E, Berti A, Besenrieder J, Bhattacharyya W, Bigongiari C, Biland A, Blanch O, Bonnoli G, Bosnjak Z, Busetto G, Carosi R, Ceribella G, Cerruti M, Chai Y, Chilingarian A, Cikota S, Colak SM, Colin U, Colombo E, Contreras JL, Cortina J, Covino S, D'Elia V, Da Vela P, Dazzi F, De Angelis A, De Lotto B, Delfino M, Delgado J, Depaoli D, Di Pierro F, Di Venere L, Espineira ED, Prester DD, Donini A, Dorner D, Doro M, Elsaesser D, Ramazani VF, Fattorini A, Ferrara G, Foffano L, Fonseca MV, Font L, Fruck C, Fukami S, Lopez RJG, Garczarczyk M, Gasparyan S, Gaug M, Giglietto N, Giordano F, Gliwny P, Godinovic N, Green D, Hadasch D, Hahn A, Herrera J, Hoang J, Hrupec D, Hutten M, Inada T, Inoue S, Ishio K, Iwamura Y, Jouvin L, Kajiwara Y, Karjalainen M, Kerszberg D, Kobayashi Y, Kubo H, Kushida J, Lamastra A, Lelas D, Leone F, Lindfors E, Lombardi S, Longo F, Lopez M, Lopez-Coto R, Lopez-Oramas A, Loporchio S, Fraga BMD, Masuda S, Maggio C, Majumdar P, Makariev M, Mallamaci M, Maneva G, Manganaro M, Mannheim K, Maraschi L, Mariotti M, Martinez M, Mazin D, Mender S, Micanovic S, Miceli D, Miener T, Minev M, Miranda JM, Mirzoyan R, Molina E, Moralejo A, Morcuende D, Moreno V, Moretti E, Munar-Adrover P, Neustroev V, Nigro C, Nilsson K, Ninci D, Nishijima K, Noda K, Nogues L, Nozaki S, Ohtani Y, Oka T, Otero-Santos J, Palatiello M, Paneque D, Paoletti R, Paredes JM, Pavletic L, Penil P, Peresano M, Persic M, Moroni PGP, Prandini E, Puljak I, Rhode W, Ribo M, Rico J, Righi C, Rugliancich A, Saha L, Sahakyan N, Saito T, Sakurai S, Satalecka K, Schleicher B, Schmidt K, Schweizer T, Sitarek J, Snidaric I, Sobczynska D, Spolon A, Stamerra A, Strom D, Strzys M, Suda Y, Suric T, Takahashi M, Tavecchio F, Temnikov P, Terzic T, Teshima M, Torres-Alba N, Tosti L, van Scherpenberg J, Vanzo G, Acosta MV, Ventura S, Verguilov V, Vigorito CF, Vitale V, Vovk I, Will M, Zaric D, Celli S, Morlino G
Publisher: EDP SCIENCES S A
Publication year: 2023
Journal: Astronomy and Astrophysics
Journal name in source: ASTRONOMY & ASTROPHYSICS
Journal acronym: ASTRON ASTROPHYS
Article number: A8
Volume number: 670
Number of pages: 20
ISSN: 0004-6361
eISSN: 1432-0746
DOI: http://dx.doi.org/10.1051/0004-6361/202038748
URL: https://www.aanda.org/articles/aa/full_html/2023/02/aa38748-20/aa38748-20.html
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 gamma 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 gamma-ray emission in the vicinity of the gamma Cygni SNR.
Methods.
We observed the region of the gamma 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 gamma-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.
