SNR G39.2-0.3, an Hadronic Cosmic Rays Accelerator. (arXiv:2007.04627v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wilhelmi_E/0/1/0/all/0/1">Emma de Ona Wilhelmi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sushch_I/0/1/0/all/0/1">Iurii Sushch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brose_R/0/1/0/all/0/1">Robert Brose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mestre_E/0/1/0/all/0/1">Enrique Mestre</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Su_Y/0/1/0/all/0/1">Yang Su</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zanin_R/0/1/0/all/0/1">Roberta Zanin</a>
Recent results obtained with gamma-ray satellites have established supernova
remnants as accelerators of GeV hadronic cosmic rays. In such processes, CRs
accelerated in SNR shocks interact with particles from gas clouds in their
surrounding. In particular, the rich medium in which core-collapse SNRs explode
provides a large target density to boost hadronic gamma-rays. SNR G39.2-0.3 is
one of the brightest SNR in infrared wavelengths, and its broad
multi-wavelength coverage allows detailed modeling of its radiation from radio
to high energies. We reanalyzed the Fermi-LAT data on this region and compare
it with new radio observations from the MWISP survey. The modeling of the
spectral energy distribution from radio to GeV energies favors an hadronic
origin of the gamma-ray emission and constrains the SNR magnetic field to be at
least ~100 uG. Despite the large magnetic field, the present acceleration of
protons seems to be limited to ~10 GeV, which points to a drastic slow down of
the shock velocity due to the dense wall traced by the CO observations,
surrounding the remnant. Further investigation of the gamma-ray spectral shape
points to a dynamically old remnant subjected to severe escape of CRs and a
decrease of acceleration efficiency. The low-energy peak of the gamma-ray
spectrum also suggests that that the composition of accelerated particles might
be enriched by heavy nuclei which is certainly expected for a core-collapse
SNR. Alternatively, the contribution of the compressed pre-existing Galactic
cosmic rays is discussed, which is, however, found to not likely be the
dominant process for gamma-ray production.
Recent results obtained with gamma-ray satellites have established supernova
remnants as accelerators of GeV hadronic cosmic rays. In such processes, CRs
accelerated in SNR shocks interact with particles from gas clouds in their
surrounding. In particular, the rich medium in which core-collapse SNRs explode
provides a large target density to boost hadronic gamma-rays. SNR G39.2-0.3 is
one of the brightest SNR in infrared wavelengths, and its broad
multi-wavelength coverage allows detailed modeling of its radiation from radio
to high energies. We reanalyzed the Fermi-LAT data on this region and compare
it with new radio observations from the MWISP survey. The modeling of the
spectral energy distribution from radio to GeV energies favors an hadronic
origin of the gamma-ray emission and constrains the SNR magnetic field to be at
least ~100 uG. Despite the large magnetic field, the present acceleration of
protons seems to be limited to ~10 GeV, which points to a drastic slow down of
the shock velocity due to the dense wall traced by the CO observations,
surrounding the remnant. Further investigation of the gamma-ray spectral shape
points to a dynamically old remnant subjected to severe escape of CRs and a
decrease of acceleration efficiency. The low-energy peak of the gamma-ray
spectrum also suggests that that the composition of accelerated particles might
be enriched by heavy nuclei which is certainly expected for a core-collapse
SNR. Alternatively, the contribution of the compressed pre-existing Galactic
cosmic rays is discussed, which is, however, found to not likely be the
dominant process for gamma-ray production.
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