Статья

The Troublesome Broadband Evolution of GRB 061126: Does a Gray Burst Imply Gray Dust?

D. A. PerleyDepartment of Astronomy, University of California, Berkeley, CA 94720-3411J. S. BloomDepartment of Astronomy, University of California, Berkeley, CA 94720-3411N. ButlerDepartment of Astronomy, University of California, Berkeley, CA 94720-3411L. K. PollackUniversity of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064Jon A. HoltzmanDepartment of Astronomy, New Mexico State University, Las Cruces, NM 88003-8001Cullen H. BlakeHarvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138D. KocevskiDepartment of Astronomy, University of California, Berkeley, CA 94720-3411W. T. VestrandLos Alamos National Laboratory, Los Alamos, NM 87545Wenyu LiDepartment of Astronomy, University of California, Berkeley, CA 94720-3411R. J. FoleyDepartment of Astronomy, University of California, Berkeley, CA 94720-3411E. BellmSpace Sciences Laboratory, University of California, Berkeley, CA 94720Hsiao‐Wen ChenDepartment of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637J. X. ProchaskaUniversity of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064D. StarrDepartment of Astronomy, University of California, Berkeley, CA 94720-3411A. V. FilippenkoDepartment of Astronomy, University of California, Berkeley, CA 94720-3411E. FalcoHarvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138Andrew SzentgyorgyiHarvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138J. WrenLos Alamos National Laboratory, Los Alamos, NM 87545P. R. WoźniakLos Alamos National Laboratory, Los Alamos, NM 87545R. J. WhiteLos Alamos National Laboratory, Los Alamos, NM 87545J. PergandeLos Alamos National Laboratory, Los Alamos, NM 87545

2008en

ABI

Аннотация

We report on observations of gamma-ray burst (GRB 061126) with an extremely bright (R ~ 12 mag at peak) early-time optical afterglow. The optical afterglow is already fading as a power-law 22 seconds after the trigger, with no detectable prompt contribution in our first exposure, which was coincident with a large prompt-emission pulse. The optical-IR photometric SED is an excellent fit to a power-law but exhibits a moderate red-to-blue evolution in the spectral index at about 500 sec. This color change is contemporaneous with a switch from a relatively fast decay to slower decay. The rapidly decaying early afterglow is broadly consistent with synchrotron emission from a reverse shock, but a bright forward shock component predicted by the intermediate- to late-time X-ray observations under the assumptions of standard afterglow models is not observed. Indeed, despite its remarkable early-time brightness this burst would qualify as a dark burst at later times on the basis of its nearly flat optical-to-X-ray spectral index. Our photometric SED provides no evidence of host extinction, requiring either large quantities of grey dust in the host system (at z=1.1588 +/- 0.0006, based upon our late-time Keck spectroscopy) or separate physical origins for the X-ray and optical afterglows. In either case, events like GRB 061126 may represent a significant fraction of observed dark bursts with faint or absent optical afterglows, suggesting a need for redress of the interpretations concerning the origin of these events, and possibly of afterglows in general.

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Идентификаторы

DOI: 10.1086/523929

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Цитирований: 5Использованных источников: 0

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