The Ep - Eiso relation and the internal shock model
Journal
Date Issued
2015
Author(s)
Description
L.N. was supported by a Marie Curie Intra-European Fellowship of the European Communitys 7th Framework Programme (PIEF-GA-2013-627715), by an ERC advanced grant (GRB) and by the I-CORE Program of the PBC and the ISF (grant 1829/12). We also thank the French Program for High Energy Astrophysics (PNHE) for financial support.
Abstract
Context. The validity of the correlation in gamma-ray bursts and the possibility of explaining the prompt emission with internal shocks are highly debated questions.
Aims: We study whether the correlation can be reproduced if internal shocks are indeed responsible for the prompt emission, or conversely, if the correlation can be used to constrain the internal shock scenario.
Methods: We developed a toy model where internal shocks are limited to the collision of only two shells. Synthetic burst populations were constructed for various distributions of the model parameters, such as the injected power in the relativistic outflow, the average Lorentz factor, and its typical contrast between the shells. These parameters can be independent or linked by various relations.
Results: Synthetic diagrams are obtained in the different cases and compared with the observed correlation. The reference observed correlation is the one defined by the BAT6 sample, a sample of Swift bursts almost complete in redshift and affected by well-known and reproducible instrumental selection effects. The comparison is then performed with a subsample of synthetic bursts that satisfy the same selection criteria as were imposed on the BAT6 sample. A satisfactory agreement between model and data can often be achieved, but only if several strong constraints are satisfied on both the dynamics of the flow and the microphysics that governs the redistribution of the shock-dissipated energy.
Aims: We study whether the correlation can be reproduced if internal shocks are indeed responsible for the prompt emission, or conversely, if the correlation can be used to constrain the internal shock scenario.
Methods: We developed a toy model where internal shocks are limited to the collision of only two shells. Synthetic burst populations were constructed for various distributions of the model parameters, such as the injected power in the relativistic outflow, the average Lorentz factor, and its typical contrast between the shells. These parameters can be independent or linked by various relations.
Results: Synthetic diagrams are obtained in the different cases and compared with the observed correlation. The reference observed correlation is the one defined by the BAT6 sample, a sample of Swift bursts almost complete in redshift and affected by well-known and reproducible instrumental selection effects. The comparison is then performed with a subsample of synthetic bursts that satisfy the same selection criteria as were imposed on the BAT6 sample. A satisfactory agreement between model and data can often be achieved, but only if several strong constraints are satisfied on both the dynamics of the flow and the microphysics that governs the redistribution of the shock-dissipated energy.
Volume
577
Start page
A31
Issn Identifier
0004-6361
Ads BibCode
2015A&A...577A..31M
Rights
open.access
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