Study of the GeV to TeV morphology of the $\gamma$-Cygni SNR (G78.2+2.1) with MAGIC and Fermi-LAT

Abstract

Context. Diffusive shock acceleration (DSA) is the most promising mechanism to accelerate Galactic cosmic rays (CRs) in the shocks of supernova remnants (SNRs). 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, we aim 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 May 2015 and September 2017 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, which can be associated with the SNR and 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.

20 pages, 10 figures. Accepted for publication in A&A. Corresponding authors: M. Strzys, G. Morlino, S. Masuda, and I. Vovk

References in corpus (13)

• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• Background Modelling in Very-High-Energy gamma-ray Astronomy
• Parametrization of gamma-ray production cross-sections for pp interactions in a broad proton energy range from the kinematic threshold to PeV energies
• Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT
• Spectral breaks as a signature of cosmic ray induced turbulence in the Galaxy
• Simultaneous Acceleration of Protons and Electrons at Nonrelativistic Quasiparallel Collisionless Shocks
• A kinetic approach to cosmic ray induced streaming instability at supernova shocks
• Galactic cosmic rays after the AMS-02 observations
• Hadronic gamma-rays from RX J1713.7-3946?
• Supernova Remnants Interacting with Molecular Clouds: X-ray and Gamma-ray Signatures
• Detailed Investigation of the Gamma-Ray Emission in the Vicinity of SNR W28 with FERMI-LAT
• A detailed X-ray investigation of PSR J2021+4026 and $\gamma$-Cygni supernova remnant
• Radio counterparts of gamma-ray sources in the Cygnus region

Cited by in corpus (5)

• Untangling PBH overproduction in $w$-SIGWs generated by Pulsar Timing Arrays for MST-EFT of single field inflation
• Detecting Relativistic Doppler in Galaxy Clustering with Tailored Galaxy Samples
• Are Kronberger 80 and/or Kronberger 82 regions PeVatron candidates for LHAASO J2108+5157?
• Fermi-LAT View on Three Ultra-high-energy 1LHAASO Sources in the $52^{\circ }<l<55^{\circ }$ Region
• Cosmological mirror symmetry and gravitational-wave helicity