MG14 - Talk detail |
Participant |
Pe'er, Asaf | |||||||
Institution |
UCC - College road - Cork - Cork - Ireland | |||||||
Session |
GB4 |
Accepted |
Yes |
Order |
3 |
Time |
15:20 | 20' |
Talk |
Oral abstract |
Title |
Hydrodynamic properties of GRB outflows based on thermal emission | |||||
Coauthors | ||||||||
Abstract |
We study the properties of a significant thermal emission component that was identified in 47 GRBs observed by different instruments. Within the framework of the ``fireball'' model, we deduce the values of the Lorentz factor \Gamma, and the acceleration radius, r_0, for these bursts. We find that all the values of \Gamma in our sample are in the range 10^2 <~\Gamma <~ 10^3, with <\Gamma>= 310. We find a very weak dependence of \Gamma on the acceleration radius r_0, \Gamma ~ r_0^\alpha with \alpha = -0.10 \pm 0.09 at \sigma = 2.1 confidence level. The mean value we find for r_0 is < r_0 > ~ 10^{8.5} cm. This higher than the gravitational radius of a 10 M_sun black hole by a factor ~ 100. We argue that this result provides an indirect evidence for jet propagation inside a massive star, and suggests the existence of recollimation shocks that take place at this radius. If time permits, I will further discuss some novel approach towards fitting GRB prompt emission spectra with physically motivated model of sub-photospheric dissipation. |
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Pdf file |
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