The high energy gamma-ray emission expected from Tycho's supernova remnant

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

Corresponding author: H. J. Völk, Heinrich.Voelk@mpi-hd.mpg.de

Received: 19 April 2002
Accepted: 24 September 2002

Abstract

A nonlinear kinetic model of cosmic ray (CR) acceleration in supernova remnants (SNRs) is used to describe the properties of Tycho's SNR. Observations of the expansion characteristics and of the nonthermal radio and X-ray emission spectra, assumed to be of synchrotron origin, are used to constrain the overall dynamical evolution and the particle acceleration parameters of the system, in addition to what is known from independent estimates of the distance and thermal X-ray observations. It is shown that a very efficient production of nuclear cosmic rays, leading to strong shock modification, and a large downstream magnetic field strength  μG are required to reproduce the observed synchrotron emission from radio to X-ray frequencies. This field strength is still well within the upper bound for the effective magnetic field, consistent with the acceleration process. The -decay γ-ray flux turns out to be somewhat greater than the inverse Compton (IC) flux off the Cosmic Microwave Background at energies below 1 TeV, dominating it strongly at 10 TeV. The predicted TeV γ-ray flux is consistent with but close to the very low upper limit recently obtained by HEGRA. A future detection at  TeV would clearly indicate hadronic emission.