Journal Article

On the hadronic γ-ray emission from Tycho's supernova remnant

Xiao Zhang, Yang Chen, Hui Li and Xin Zhou

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 429, issue 1, pages L25-L29
Published in print February 2013 |
Published online November 2012 | e-ISSN: 1745-3933 | DOI: http://dx.doi.org/10.1093/mnrasl/sls016

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Hadronic γ-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 γ-ray emission. Among them, however, it is the only one in which the hadronic emission is proposed to arise from the interaction with a low-density (∼0.3 cm−3) ambient medium. Here we present an alternative hadronic explanation with a modest energy conversion efficiency (of the order of 1 per cent) for this young remnant. With such an efficiency, a normal electron-to-proton ratio (of the order of 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 γ-ray flux. This result is consistent with the multiband evidence of the presence of a dense medium from the north to the east of the Tycho SNR. The SNR–cloud association, in combination with the H i absorption data, helps to constrain the so-far controversial distance to Tycho and leads to an estimate of 2.5 kpc.

Keywords: radiation mechanisms: non-thermal; ISM: individual objects: Tycho; ISM: supernova remnants; gamma-rays: ISM

Journal Article.  3701 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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