HYDRODYNAMIC PROPERTIES of GAMMA-RAY BURST OUTFLOWS DEDUCED from the THERMAL COMPONENT

Asaf Pe'Er, Hugh Barlow, Shane O'Mahony, Raffaella Margutti, Felix Ryde, Josefin Larsson, Davide Lazzati, Mario Livio

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

We study the properties of a significant thermal emission component that was identified in 47 gamma-ray bursts observed by different instruments. Within the framework of the "fireball" model, we deduce the values of the Lorentz factor Γ, and the acceleration radius, r0, for these bursts. We find that all the values of Γ in our sample are in the range with . We find a very weak dependence of Γ on the acceleration radius r0, with α = -0.10 ± 0.09 at the σ = 2.1 confidence level. The values of r0 span a wide range, cm, with a mean value of cm. This is higher than the gravitational radius of a 10 Mo black hole by a factor of ≈30. We argue that this result provides indirect evidence for jet propagation inside a massive star, and suggests the existence of recollimation shocks that take place close to this radius.

Original languageEnglish
Article number127
JournalAstrophysical Journal
Volume813
Issue number2
DOIs
StatePublished - 10 Nov 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved..

Funding

FundersFunder number
National Science Foundation1066293
Seventh Framework Programme618499

    Keywords

    • gamma rays: stars
    • hydrodynamics
    • methods: data analysis
    • radiation mechanisms: thermal
    • radiative transfer

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