Failed gamma-ray bursts and orphan afterglows

  title={Failed gamma-ray bursts and orphan afterglows},
  author={Y. F. Huang and Z. G. Dai and Tan Lu},
  journal={Monthly Notices of the Royal Astronomical Society},
It is believed that orphan afterglow searches can help to measure the beaming angle in gamma-ray bursts (GRBs). Great expectations have been put on this method. We point out that the method is in fact not as simple as we originally expected. As a result of the baryon-rich environment that is common to almost all popular progenitor models, there should be many failed gamma-ray bursts, i.e. fireballs with Lorentz factor much less than 100-1000, but still much larger than unity. In fact, the… 

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