Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-10-05
Astrophys.J.642:995-1003,2006
Astronomy and Astrophysics
Astrophysics
Discussion added on the results of Baring & Braby (2004); Accepted for publication in Ap.J
Scientific paper
10.1086/501424
A thermal radiative component is likely to accompany the first stages of the prompt emission of Gamma-ray bursts (GRB's) and X-ray flashes (XRF's). We analyze the effect of such a component on the observable spectrum, assuming that the observable effects are due to a dissipation process occurring below or near the thermal photosphere. We consider both the internal shock model and a 'slow heating' model as possible dissipation mechanisms. For comparable energy densities in the thermal and the leptonic component, the dominant emission mechanism is Compton scattering. This leads to a nearly flat energy spectrum (\nu F_\nu \propto \nu^0) above the thermal peak at ~10-100 keV and below 10-100 MeV, for a wide range of optical depths 0.03 <~ \tau_{\gamma e} <~ 100, regardless of the details of the dissipation mechanism or the strength of the magnetic field. At lower energies steep slopes are expected, while above 100 MeV the spectrum depends on the details of the dissipation process. For higher values of the optical depth, a Wien peak is formed at 100 keV - 1 MeV, and no higher energy component exists. For any value of \tau_{\gamma e}, the number of pairs produced does not exceed the baryon related electrons by a factor larger than a few. We conclude that dissipation near the thermal photosphere can naturally explain both the steep slopes observed at low energies and a flat spectrum above 10 keV, thus providing an alternative scenario to the optically thin synchrotron - SSC model.
Meszaros Peter
Pe'er Asaf
Rees Martin J.
No associations
LandOfFree
The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum 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 The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-249570