Astron. Astrophys. Suppl. Ser. 138, 527-528
G. Ghisellini1 and A. Celotti2
1 - Osservatorio Astronomico di Brera, via Bianchi 46, I-23807 Merate, Italy
2 - S.I.S.S.A., via Beirut 2-4, I-34014, Italy
Received December 18, 1998; accepted January 26, 1999
Quasi-thermal Comptonization in internal shocks formed between relativistic shells can account for the high energy emission of gamma-ray bursts (GRB). This is the dominant cooling mechanism if the typical energy of the emitting particles is achieved either through the balance between heating and cooling or as a result of electron-positron (e) pair production. Both processes yield sub/mildly relativistic energies. In this case the synchrotron spectrum is self-absorbed, providing the seed photons for the Comptonization process, whose spectrum is flat [const], ending either in an exponential cutoff or a Wien peak.
Key words: gamma rays: bursts -- radiation mechanisms: non-thermal, thermal -- X-rays: general
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