EDP Sciences
Free Access
Volume 400, Number 3, March IV 2003
Page(s) 971 - 980
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20030033

A&A 400, 971-980 (2003)
DOI: 10.1051/0004-6361:20030033

Gamma-ray emission from Cassiopeia A produced by accelerated cosmic rays

E. G. Berezhko1, G. Pühlhofer2 and H. J. Völk2

1  Institute of Cosmophysical Research and Aeronomy, 31 Lenin Ave., 677891 Yakutsk, Russia
    e-mail: berezhko@ikfia.ysn.ru
2  Max Planck Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
    e-mail: Gerd.Puehlhofer@mpi-hd.mpg.de

(Received 23 September 2002 / Accepted 7 January 2003 )

The nonlinear kinetic model of cosmic ray (CR) acceleration in supernova remnants (SNRs) is used to describe the relevant properties of Cassiopeia A (Cas A). In order to reproduce the SNR's observed size, expansion rate and thermal X-ray emission we employ a piecewise homogeneous model for the progenitor's circumstellar medium developed by Borkowski et al. (1996). It consists of a tenuous inner wind bubble, a dense shell of swept-up red supergiant wind material, and a subsequent red supergiant wind region. A quite large SNR interior magnetic field $B_\mathrm{d}\approx 1\,\mathrm{mG}$ is required to give a good fit for the radio and X-ray synchrotron emission. The steep radio spectrum is consistent with efficient proton acceleration which produces a significant shock modification and leads to a steep electron spectrum at energies $\epsilon_{\mathrm{e}}<1\,\mathrm{GeV}$. The calculated integral $\gamma$-ray flux from Cas A, $F_{\gamma}\propto \epsilon_{\gamma}^{-1}$, is dominated by $\pi^0$-decay $\gamma$-rays due to relativistic protons. It extends up to roughly $30\,\mathrm{TeV}$ if CR diffusion is as strong as the Bohm limit. At TeV energies it satisfactorily agrees with the value $5.8\times 10^{-13}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}$ detected by the HEGRA collaboration.

Key words: supernovae: individual: Cassiopeia A -- cosmic rays -- gamma rays: theory -- acceleration of particles -- shock waves -- radiation mechanisms: non-thermal

Offprint request: H. J. Völk, Heinrich.Voelk@mpi-hd.mpg.de

SIMBAD Objects

© ESO 2003

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.