Astronomy and Astrophysics – Astrophysics – High Energy Astrophysical Phenomena
Scientific paper
2010-08-13
Astronomy and Astrophysics
Astrophysics
High Energy Astrophysical Phenomena
15 pages 4 figuers
Scientific paper
Fermi observations of GeV emission from GRBs have suggested that the Lorentz factor of some GRBs is around a thousand or even higher. At the same time the same Fermi observations have shown an extended GeV emission indicating that this higher energy emission might be a part of the afterglow and it does not come from the same region as the lower energy prompt emission. If this interpretation is correct than we should reconsider the opacity limits on the Loretnz factor of the emitting regions which are based on a one-zone model. We describe here a two-zone model in which the GeV photons are emitted in a larger radius than the MeV photons and we calculate the optical depth for pair creation of a GeV photon passing the lower energy photons shell. We find that, as expected, the new two-zone limits on the Lorentz factor are significantly lower. The corresponding limits for the Fermi bursts are lower by a factor of ?two to five compared to the one-zone model and it is possible that both the MeV and GeV regions have relatively modest Lorentz factors (~200 - 400).
Fan Yi-Zhong
Piran Tsvi
Zou Yuan-Chuan
No associations
LandOfFree
A Revised Limit of the Lorentz Factors of GRBs with Two Emitting Regions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Revised Limit of the Lorentz Factors of GRBs with Two Emitting Regions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Revised Limit of the Lorentz Factors of GRBs with Two Emitting Regions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-502953