Unsteady outflow models for cosmological gamma-ray bursts

M. J. Rees, P. Mészáros

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Abstract

The "event" that triggers a gamma-ray burst cannot last for more than a few seconds. This is, however, long compared with the dynamical timescale of a compact stellar-mass object (∼10-3 s). Energy is assumed to be released as an outflow with high mean Lorentz factor Γ. But a compact stellar-mass collapse or merger is, realistically, likely to generate a mass (or energy) flux that is unsteady on some timescales in the range 10-3-10 s. If Γ fluctuates by a factor of ∼2 around its mean value, relative motions within the outflowing material will themselves (in the comoving frame) be relativistic, and can give rise to internal shocks. For Γ ∼102, the resultant dissipation occurs outside the "photosphere" and can convert a substantial fraction of the overall outflow energy into nonthermal radiation. This suggests a mechanism for cosmological bursts that demands less extreme assumptions (in respect of Γ-values, freedom from baryonic contamination, etc.) than earlier proposals.

Original languageEnglish (US)
Pages (from-to)L93-L96
JournalAstrophysical Journal
Volume430
Issue number2 PART 2
DOIs
StatePublished - Aug 1 1994

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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