Astron. Astrophys. Suppl. Ser.
Volume 138, Number 3, September 1999Gamma-Ray Bursts in the Afterglow Era Contents Rome, November 3-6, 1998
|Page(s)||499 - 502|
|Published online||15 September 1999|
Central engines for gamma-ray bursts
Astronomy Department, UCSC, Santa Cruz, CA 95064, U.S.A.
Send offprint request to: S.E. Woosley
Accepted: 10 March 1999
What powers a gamma-ray burst (GRB)? We discuss here some properties of several currently favored models based on black hole accretion with emphasis on the collapsar - a rotating massive star whose iron core collapse produces a black hole. Depending on mass, rotation rate, and viewing angle, collapsars can explain a wide gambit of GRBs from faint events like GRB 980425, to bright ones like GRB 971214. Because of accretion disk instabilities, the Γ in the jet may be rapidly time variable. The burst itself is made by a combination of internal shocks in the jet and external shocks with the pre-explosive stellar wind. Beaming for hard gamma-rays is about 1%, but mildly relativistic matter is ejected at larger angles. All collapsars produce Type Ib/c supernovae like SN 1998bw, but the converse is not true. Most Type Ib/c supernovae do not make GRBs.
Key words: black holes / accretion; gamma-ray bursts
© European Southern Observatory (ESO), 1999