GRBs: when do blackbody spectra look like non-thermal ones?

Blinnikov, S. I.; Kozyreva, A. V.; Panchenko, I. E.

GRBs: when do blackbody spectra look like non-thermal ones?

Authors

Blinnikov, S. I.

Kozyreva, A. V.

Panchenko, I. E.

Description

We argue that a nonthermally looking spectrum of a gamma-ray burst (GRB) can be formed as a superposition of a set of thermal blackbody spectra. This superposition may be done by time integration which is present even in `time resolved' GRB spectroscopy. A nonthermal spectrum can be obtained also by the space integration which should take place unless all the emission comes from a plane front moving exactly towards the observer. We propose a model of the gamma-ray burst spectrum formation based on this idea. This model allows the GRB radiation to be optically thick and to have higher values of baryon load. Thus the latter is limited by the energy considerations only, and not by the condition of a small optical depth.
17 pages, 8 figures. Reported partly at Stockholm Observatory on May 15, 1998, and at the International Winter School "Physics of Space" held at the Urals State University on Feb. 2-6,1998