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2014 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 784, no 2, L43Article in journal (Refereed) Published
Abstract [en]

Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal gamma-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, E-p and kT, of these two components are correlated via the relation E-p proportional to T-alpha which varies from GRB to GRB. We present an interpretation in which the value of the index alpha indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.

Place, publisher, year, edition, pages
2014. Vol. 784, no 2, L43
Keyword [en]
gamma-ray burst: general, radiation mechanisms: non-thermal, radiation mechanisms: thermal
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
URN: urn:nbn:se:su:diva-103974DOI: 10.1088/2041-8205/784/2/L43ISI: 000333333400026OAI: diva2:721815


Available from: 2014-06-05 Created: 2014-05-27 Last updated: 2015-04-13Bibliographically approved

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Iyyani, ShabnamAxelsson, Magnus
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Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)Department of Astronomy
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