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High-energy Emission Components in the Short GRB 090510

Corsi, Alessandra and Guetta, Dafne and Piro, Luigi (2010) High-energy Emission Components in the Short GRB 090510. Astrophysical Journal, 720 (2). pp. 1008-1015. ISSN 0004-637X.

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We investigate the origin of the prompt and delayed emission observed in the short GRB 090510. We use the broadband data to test whether the most popular theoretical models for gamma-ray burst emission can accommodate the observations for this burst. We first attempt to explain the soft-to-hard spectral evolution associated with the delayed onset of a GeV tail with the hypothesis that the prompt burst and the high-energy tail both originate from a single process, namely, synchrotron emission from internal shocks (IS). Considerations on the compactness of the source imply that the high-energy tail should be produced in a late-emitted shell, characterized by a Lorentz factor greater than the one generating the prompt burst. However, in this hypothesis, the predicted evolution of the synchrotron peak frequency does not agree with the observed soft-to-hard evolution. Given the difficulties of a single-mechanism hypothesis, we test two alternative double-component scenarios. In the first, the prompt burst is explained as synchrotron radiation from IS and the high-energy emission (up to about 1 s following the trigger) as IS synchrotron-self-Compton. In the second scenario, in view of its long duration (~100 s), the high-energy tail is decoupled from the prompt burst and has an external shock origin. In this case, we show that a reasonable choice of parameters does indeed exist to accommodate the optical-to-GeV data, provided the Lorentz factor of the shocked shell is sufficiently high. Finally, we attempt to explain the chromatic break observed around ~10^3 s with a structured jet model. We find that this might be a viable explanation and that it lowers the high value of the burst energy derived by assuming isotropy, ~10^(53) erg, below ~10^(49) erg, which is more compatible with the energetics from a binary merger progenitor.

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Additional Information:© 2010. The American Astronomical Society. All rights reserved. Received 2009 November 23; accepted 2010 July 13; published 2010 August 16. The authors are grateful to Patrick Sutton for helping improve the manuscript by carefully proofreading its final version. A.C. thanks the Italian L’Oréal-UNESCO program “For Women in Science,” and EGO—European Gravitational Wave Observatory, for support. The authors also acknowledge the support of ASI-INAF contract I/088/06/0.
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Subject Keywords:gamma-ray burst: individual (GRB 090510); radiation mechanisms: non-thermal; X-rays: bursts
Classification Code:PACS: 98.70.Rz; 95.30.Gv; 95.30.Cq
Record Number:CaltechAUTHORS:20100928-133554737
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Official Citation:Alessandra Corsi et al 2010 ApJ 720 1008 doi: 10.1088/0004-637X/720/2/1008
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20200
Deposited By: Ruth Sustaita
Deposited On:28 Sep 2010 22:56
Last Modified:26 Dec 2012 12:28

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