Efficiency Crisis of Swift Gamma-Ray Bursts with Shallow X-ray Afterglows: Prior Activity or Time-Dependent Microphysics?

Preprint
Publisher Website
Google Scholar
  • 27 November 2005
Abstract
Most X-ray afterglows of gamma-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase t^{-1/2} in the first thousands of seconds. We discuss that the shallow decay requires an unreasonably high gamma-ray efficiency, > 75-90%, within current models, which is difficult to be produced by internal shocks. Such a crisis may be avoided if a weak relativistic explosion occurs ~ 10^3-10^6 s prior to the main burst or if the energy fraction that goes into electrons increases during the shallow decay, \epsilon_e ~ t^{1/2}. The former model predicts a very long precursor while either model would prefer dim optical flashes from the reverse shock as recently reported.

This publication has 0 references indexed in Scilit: