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TeV Gamma-Rays from Old Supernova Remnants

Ryo Yamazaki·Kazunori Kohri·Aya Bamba·Tatsuo Yoshida·Toru Tsuribe·Fumio Takahara
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Abstract

We study the emission from an old supernova remnant (SNR) with an age of around 10^5 yrs and that from a giant molecular cloud (GMC) encountered by the SNR. When the SNR age is around 10^5 yrs, proton acceleration is efficient enough to emit TeV gamma-rays both at the shock of the SNR and that in the GMC. The maximum energy of primarily accelerated electrons is so small that TeV gamma-rays and X-rays are dominated by hadronic processes, pi^0-decay and synchrotron radiation from secondary electrons, respectively. However, if the SNR is older than several 10^5 yrs, there are few high-energy particles emitting TeV gamma-rays because of the energy loss effect and/or the wave damping effect occurring at low-velocity isothermal shocks. For old SNRs or SNR-GMC interacting systems capable of generating TeV gamma-ray emitting particles, we calculated the ratio of TeV gamma-ray (1-10 TeV) to X-ray (2-10 keV) energy flux and found that it can be more than ~10^2. Such a source showing large flux ratio may be a possible origin of recently discovered unidentified TeV sources.

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Ryo Yamazaki, Kazunori Kohri, Aya Bamba, Tatsuo Yoshida, Toru Tsuribe, Fumio Takahara. 2006-07-19. TeV Gamma-Rays from Old Supernova Remnants. https://doi.org/10.1111/j.1365-2966.2006.10832.x

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