Gamma-ray Bursts (GRBs) are powerful explosions that emit
most of their energy, as their name suggests, in gamma-rays of typical energies
of about 1 MeV. This emission lasts for about two minutes or less and it is called the prompt emission. The isotropic energy radiated in GRBs is equivalent to the energy that the
Sun will radiate in its entire lifetime. After decades of studying
this cosmological phenomenon, we have come to learn that it involves
a collimated and relativistic jet. Also, we know that they
radiate energy in the X-ray, optical and radio bands for days, weeks and years, respectively, which is called the
afterglow. Recently, NASA's Fermi Satellite was launched and,
in addition to MeV photons, it detected GeV photons from these astrophysical sources.
We show that these GeV photons are produced when the GRB jet interacts with the medium
that surrounds it: the external forward shock model. We arrive at this conclusion
not only by studying the GeV emission, but also by studying the afterglow observations
(Chapter 2). We corroborate this model by studying the electron acceleration
in the external forward shock model and find that electrons can radiate at the maximum observed
energy of ~ 10 GeV (Chapter 3). We also provide an extensive analysis of the most recent
afterglow observations of GRB 090902B within the same
framework of an external forward shock origin. We find
that the data for this burst requires a small deviation from the
traditionally used power-law electron energy distribution, however,
our previous results remain unchanged (Chapter 4). To conclude,
we use the end of the prompt emission phase, which exhibits a
steep X-ray temporal decay, to constrain the behavior of the
central engine responsible for launching the relativistic jet (Chapter 5). / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2011-05-3048 |
| Date | 16 June 2011 |
| Creators | Barniol Duran, Rodolfo Jose |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | thesis |
| Format | application/pdf |
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