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

21 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 (US)
Article number127
JournalAstrophysical Journal
Volume813
Issue number2
DOIs
StatePublished - Nov 10 2015

Keywords

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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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