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- · arXiv e-print (arXiv:1108.0929)
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| Title: |
| Magnetic jet model for GRBs and the delayed arrival of >100 MeV photons |
| Authors: |
| Bosnjak, Z.; Kumar, P. |
| Publication: |
| eprint arXiv:1108.0929 |
| Publication Date: |
| 08/2011 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics - High Energy Astrophysical Phenomena |
| Comment: |
| 5 pages; submitted to MNRAS |
| Bibliographic Code: |
| 2011arXiv1108.0929B |
Abstract
Photons of energy larger than 100 MeV from long-GRBs arrive a few seconds after <10 MeV photons do. We show that this delay is a natural consequence of a magnetic dominated relativistic jet. The much slower acceleration of a magnetic jet with radius (compared with a hot baryonic outflow) results in high energy gamma-ray photons to be converted to electron-positron pairs out to a larger radius whereas lower energy gamma-rays of energy less than ~10 MeV can escape when the jet crosses the Thomson-photosphere. The resulting delay for the arrival of high energy photons is found to be similar to the value observed by the Fermi satellite for a number of GRBs. A prediction of this model is that the delay should increase with photon energy (E) as E^{0.17} for E>100 MeV. The delay depends almost linearly on burst redshift, and on the distance from the central compact object where the jet is launched (R_0). Therefore, the delay in arrival of >10^2 MeV photons can be used to estimate burst redshift if the magnetic jet model for gamma-ray generation is correct and R_0 is roughly the same for long-GRBs.
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