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Observations, theory and implications of thermal emission from gamma-ray bursts
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0002-9769-8016
2010 (English)In: The Shocking Universe: Gamma-Ray Bursts and High Energy Shock phenomena, 2010Conference paper (Other academic)
Abstract [en]

Recent analyses show evidence for a thermal emission component that accompanies the non-thermal emission during the prompt phase of GRBs. First, we show the evidence for the existence of this component; Second, we show that this component is naturally explained by considering emission from the photosphere, taking into account high latitude emission from optically thick relativistically expanding plasma. We show that the thermal flux is expected to decay at late times as F_BB ~ t\^$$-2$$, and the observed temperature as T ~ t\^$$-$$alpha$$, with $$alpha ~ 1/2 - 2/3. These theoretical predictions are in very good agreement with the observations. Finally, we discuss three implications of this interpretation: (a) The relation between thermal emission and high energy, non-thermal spectra observed by Fermi. (b) We show how thermal emission can be used to directly measure the Lorentz factor of the flow and the initial radius of the jet. (c) We show how the lack of detection of the thermal component can be used to constrain the composition of GRB jets.

Place, publisher, year, edition, pages
Keyword [en]
Astrophysics - High Energy Astrophysical Phenomena
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-81240OAI: diva2:497499
The Shocking Universe - Gamma-Ray Bursts and High Energy Shock phenomena, Venice, 14-18 September 2009
QC 20120418Available from: 2012-02-10 Created: 2012-02-10 Last updated: 2012-04-18Bibliographically approved

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