Gamma-ray emission expected from Kepler's supernova remnant

¹ Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, 31 Lenin Ave., 677980 Yakutsk, Russia e-mail: berezhko@ikfia.ysn.ru
² Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany e-mail: Heinrich.Voelk@mpi-hd.mpg.de

Received: 3 January 2006
Accepted: 19 January 2006

Abstract

Aims.Nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova remnants (SNRs) is used to investigate the properties of Kepler's SNR and, in particular, to predict the γ-ray spectrum expected from this SNR.

Methods.Observations of the nonthermal radio and X-ray emission spectra as well as theoretical constraints for the total supernova (SN) explosion energy E_sn are used to constrain the astronomical and particle acceleration parameters of the system.

Results.Under the assumption that Kepler's SN is a type Ia SN we determine for any given explosion energy E_sn and source distance d the mass density of the ambient interstellar medium (ISM) from a fit to the observed SNR size and expansion speed. This makes it possible to make predictions for the expected γ-ray flux. Exploring the expected distance range we find that for a typical explosion energy  erg the expected energy flux of TeV γ-rays varies from 2  10^-11 to 10^-13 erg/(cm² s) when the distance changes from  kpc to 7 kpc. In all cases the γ-ray emission is dominated by -decay γ-rays due to nuclear CRs. Therefore Kepler's SNR represents a very promising target for instruments like HESS, CANGAROO and GLAST. A non-detection of γ-rays would mean that the actual source distance is larger than 7 kpc.