Unsteady Outflow Models for Cosmological GammaRay Bursts
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 stellarmass object ($\sim 10^{3}$ seconds). Energy is assumed to be released as an outflow with high mean lorentz factor $\Gamma$. But a compact stellarmass 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 seconds. If $\Gamma$ fluctuates by a factor of $\sim 2$ 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 $\Gamma \sim 10^2$, 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 $\Gamma$values, freedom from baryonic contamination, etc) than earlier proposals.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 1994
 DOI:
 10.1086/187446
 arXiv:
 arXiv:astroph/9404038
 Bibcode:
 1994ApJ...430L..93R
 Keywords:

 Compacting;
 Gamma Ray Bursts;
 Mathematical Models;
 Stellar Mass;
 Baryons;
 Collapse;
 Lorentz Contraction;
 Relativistic Velocity;
 Shock Waves;
 Space Radiation;
 COSMOLOGY: MISCELLANEOUS;
 GAMMA RAYS: BURSTS;
 GAMMA RAYS: THEORY;
 Astrophysics
 EPrint:
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