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The anatomy of a long gamma-ray burst: a simple classification scheme for the emission mechanism(s)
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0003-3345-9515
2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 820, no 1, 68Article in journal (Refereed) PublishedText
Abstract [en]

Ultra-relativistic motion and efficient conversion of kinetic energy to radiation are required by gamma-ray burst (GRB) observations, yet they are difficult to simultaneously achieve. Three leading mechanisms have been proposed to explain the observed emission emanating from GRB outflows: radiation from either relativistic internal or external shocks, or thermal emission from a photosphere. Previous works were dedicated to independently treating these three mechanisms and arguing for a sole, unique origin of the prompt emission of GRBs. In contrast, herein, we first explain why all three models are valid mechanisms and that a contribution from each of them is expected in the prompt phase. Additionally, we show that a single parameter, the dimensionless entropy of the GRB outflow, determines which mechanism contributes the most to the emission. More specifically, internal shocks dominate for low values of the dimensionless entropy, external shocks for intermediate values, and finally, photospheric emission for large values. We present a unified framework for the emission mechanisms of GRBs with easily testable predictions for each process.

Place, publisher, year, edition, pages
The American Astronomical Society , 2016. Vol. 820, no 1, 68
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-184433DOI: 10.3847/0004-637X/820/1/68ISI: 000372787000067ScopusID: 2-s2.0-84961601423OAI: diva2:916029

QC 20160419

Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2016-04-25Bibliographically approved

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