Extended Power-Law Decays in BATSE Gamma-Ray Bursts: Signatures of External Shocks?
| Autor: | Chryssa Kouveliotou, Ralph A. M. J. Wijers, Michael S. Briggs, Timothy W. Giblin, Valerie Connaughton, J. van Paradijs, Gerald J. Fishman, Robert D. Preece |
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| Přispěvatelé: | High Energy Astrophys. & Astropart. Phys (API, FNWI) |
| Rok vydání: | 2002 |
| Předmět: |
Physics
Jet (fluid) Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Phase (waves) Astronomy FOS: Physical sciences Astronomy and Astrophysics Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Power law Afterglow Synchrotron emission Lorentz factor symbols.namesake Space and Planetary Science Angular diameter symbols Spectral analysis Gamma-ray burst Adiabatic process Blast wave |
| Zdroj: | Astrophysical Journal, 570(2), 573-587. IOP Publishing Ltd. GAMMA-RAY BURST AND AFTERGLOW ASTRONOMY 2001: A Workshop Celebrating the First Year of the HETE Mission, 273-275 STARTPAGE=273;ENDPAGE=275;TITLE=GAMMA-RAY BURST AND AFTERGLOW ASTRONOMY 2001: A Workshop Celebrating the First Year of the HETE Mission |
| ISSN: | 0004-637X |
| DOI: | 10.1086/339622 |
| Popis: | The connection between Gamma-Ray Bursts (GRBs) and their afterglows is currently not well understood. Afterglow models of synchrotron emission generated by external shocks in the GRB fireball model predict emission detectable in the gamma-ray regime ($\gax 25$ keV). In this paper, we present a temporal and spectral analysis of a subset of BATSE GRBs with smooth extended emission tails to search for signatures of the ``early high-energy afterglow'', i.e., afterglow emission that initially begins in the gamma-ray phase and subsequently evolves into X-Ray, uv, optical, and radio emission as the blast wave is decelerated by the ambient medium. From a sample of 40 GRBs we find that the temporal decays are best described with a power-law $\sim t^{\beta}$, rather than an exponential, with a mean index $ \approx -2$. Spectral analysis shows that $\sim 20%$ of these events are consistent with fast-cooling synchrotron emission for an adiabatic blast wave; three of which are consistent with the blast wave evolution of a jet, with $F_{\nu} \sim t^{-p}$. This behavior suggests that, in some cases, the emission may originate from a narrow jet, possibly consisting of ``nuggets'' whose angular size are less than $1 / \Gamma$, where $\Gamma$ is the bulk Lorentz factor. Comment: 17 pages, 4 color PostScript figures, to appear in ApJ May 10, 2002 issue |
| Databáze: | OpenAIRE |
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