Open AccessThe expected thermal precursors of gamma‐ray bursts in the internal shock model
Author(s) -
Daigne Frédéric,
Mochkovitch Robert
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05875.x
Subject(s) - physics , lorentz factor , astrophysics , thermal , shock (circulatory) , kinetic energy , thermal radiation , thermal emission , cosmic ray , radiation , particle acceleration , gamma ray , shock wave , acceleration , gamma ray burst , lorentz transformation , mechanics , classical mechanics , optics , meteorology , medicine , thermodynamics
The prompt emission of gamma‐ray bursts probably comes from a highly relativistic wind which converts part of its kinetic energy into radiation via the formation of shocks within the wind itself. Such ‘internal shocks’ can occur if the wind is generated with a highly non‐uniform distribution of the Lorentz factor. We estimate the expected photospheric emission of such a relativistic wind when it becomes transparent. We compare this thermal emission (temporal profile + spectrum) with the non‐thermal emission produced by the internal shocks. In most cases, we predict a rather bright thermal emission that should already have been detected. This favours acceleration mechanisms for the wind where the initial energy input is under magnetic rather than thermal form. Such scenarios can produce thermal X‐ray precursors comparable to those observed by Ginga and WATCH/GRANAT.