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Astron. Astrophys. 355, 211-220 (2000)


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On the gamma-ray fluxes expected from Cassiopeia A

A.M. Atoyan 1,2, F.A. Aharonian 1, R.J. Tuffs 1 and H.J. Völk 1

1 Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
2 Yerevan Physics Institute, 375036 Yerevan, Armenia

Received 9 July 1999 / Accepted 13 December 1999

Abstract

Based on the results of our previous study of the broad band synchrotron emission of Cas A in the framework of a spatially inhomogeneous model, we calculate the fluxes of [FORMULA]-radiation that can be expected from this supernova remnant in different energy bands. We show that at energies below 10 GeV [FORMULA]-ray fluxes detectable by forthcoming space-borne detectors should be inevitably produced due to bremsstrahlung of radio emitting electrons. We predict that the power-law index of the photon flux in the GeV region should be hard, close to the index [FORMULA] expected for the acceleration spectrum of electrons in compact bright radio structures. Photon fluxes accessible to future ground-based [FORMULA]-ray detectors could also be expected at very high energies. The fluxes to be expected due to bremsstrahlung and inverse Compton radiation of relativistic electrons at TeV energies should be very steep, and strongly dependent on the characteristic magnetic fields in Cas A. We could expect also significant fluxes of [FORMULA]-decay [FORMULA]-rays produced by relativistic protons which presumably are also accelerated in Cas A. These fluxes may extend with a hard spectrum beyond TeV energies as far as the protons could be accelerated to energies [FORMULA]. The hardness of the [FORMULA]-ray spectrum at TeV energies could in principle allow one to distinguish between electronic and hadronic origins of those [FORMULA]-rays. We discuss also other implications, such as relativistic particle content, or physical parameters in the source, that could be derived from future [FORMULA]-ray flux measurements in different energy bands.

Key words: acceleration of particles – radiation mechanisms: non-thermal – stars: supernovae: individual: Cas A – gamma rays: theory – radio continuum: ISM

Send offprint requests to: Felix.Aharonian@mpi-hd.mpg.de

© European Southern Observatory (ESO) 2000

Online publication: March 17, 2000

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