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- · arXiv e-print (arXiv:1009.2326)
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| Title: |
| Jet propagations, breakouts and photospheric emissions in collapsing massive progenitors of long duration gamma ray bursts |
| Authors: |
| Nagakura, Hiroki; Ito, Hirotaka; Kiuchi, Kenta; Yamada, Shoichi |
| Publication: |
| eprint arXiv:1009.2326 |
| Publication Date: |
| 09/2010 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics - High Energy Astrophysical Phenomena |
| Comment: |
| submitted to ApJL |
| Bibliographic Code: |
| 2010arXiv1009.2326N |
Abstract
We investigate by two-dimensional axisymmetric relativistic hydrodynamical simulations (1) gravitational collapse of a rapidly rotating massive star, which is supposed to be a progenitor of long duration gamma ray bursts (GRBs), (2) jet propagations through the collapsing envelopes, (3) breakouts and subsequent expansions into stellar winds and (4) accompanying photospheric emissions. We pay particular attention to observational consequences of the difference in the timing of jet injection. We find that although the envelope moves inwards initially owing to the decrease of pressure, the outer part stops shrinking eventually when the centrifugal force becomes large enough. Then the shock wave is formed, propagates outwards and breaks out of the envelope into the stellar wind. Which of the jet and shock breaks out earlier depends on the timing of jet injection. If the shock breakout occurs first owing to later injection, the jet propagation and subsequent photospheric emissions are affected substantially. In the calculation of optical depths to find the location of the photosphere, the densities and temperatures at appropriate retarded times are extracted from the hydrodynamical data. We show that the luminosity and observed temperature of the photospheric emissions are both much lower than those reported in the previous studies, which neglected the time retardation in the calculation of optical depths. Our results imply that a fraction of photons should be somehow upscattered if the photospheric emissions are responsible for the prompt emission of GRBs.
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