On the Hadronic Gamma-ray Emission from Tycho's Supernova Remnant
Abstract
Hadronic gamma-ray emission from supernova remnants (SNRs) is an important tool to test shock acceleration of cosmic ray protons. Tycho is one of nearly a dozen Galactic SNRs which are suggested to emit hadronic gamma-ray emission. Among them, however, it is the only one in which the hadronic emission is proposed to arise from the interaction with low-density (~0.3 cm^{-3}) ambient medium. Here we present an alternative hadronic explanation with a modest conversion efficiency (of order 1%) for this young remnant. With such an efficiency, a normal electron-proton ratio (of order 10^{-2}) is derived from the radio and X-ray synchrotron spectra and an average ambient density that is at least one-order-of-magnitude higher is derived from the hadronic gamma-ray flux. This result is consistent with the multi-band evidence of the presence of dense medium from the north to the east of the Tycho SNR. The SNR-cloud association, in combination with the HI absorption data, helps to constrain the so-far controversial distance to Tycho and leads to an estimate of 2.5 kpc.
Keywords
Cite
@article{arxiv.1210.4769,
title = {On the Hadronic Gamma-ray Emission from Tycho's Supernova Remnant},
author = {Xiao Zhang and Yang Chen and Hui Li and Xin Zhou},
journal= {arXiv preprint arXiv:1210.4769},
year = {2015}
}
Comments
5 pages (including 2 figures), accepted for publication in MNRAS Letter