Efficiency Crisis of Swift Gamma-Ray Bursts with Shallow X-ray Afterglows : Prior Activity or Time-Dependent Microphysics?
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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 ~ 103-106 s prior to the main burst or if the energy fraction that goes into electrons increases during the shallow decay, e t1/2. The former model predicts a very long precursor while either model would prefer dim optical flashes from the reverse shock as recently reported.
Journal
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- Astronomy and Astrophysics
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Astronomy and Astrophysics 458 (1), 7-12, 2006-10
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Details
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- CRID
- 1050014791011199104
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- NII Article ID
- 120000878155
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- NII Book ID
- AA00553195
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- Text Lang
- en
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- Article Type
- journal article
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- Data Source
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- IRDB
- CiNii Articles
- KAKEN