Статья

GRB 090417B AND ITS HOST GALAXY: A STEP TOWARD AN UNDERSTANDING OF OPTICALLY DARK GAMMA-RAY BURSTS

K. L. PageAstrophysics Science Division, Code 660.1, 8800 Greenbelt Road Goddard Space Flight Centre, Greenbelt, MD 20771, USA; [email protected]B. SbarufattiINAF–IASF, Via Ugo La Malfa 153, I-90146 Palermo, ItalyRong-Feng ShenDepartment of Astronomy, University of Texas, Austin, TX 78712, USAP. SchadyMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking Surrey RH5 6NT, UKJay CummingsAstrophysics Science Division, Code 660.1, 8800 Greenbelt Road Goddard Space Flight Centre, Greenbelt, MD 20771, USA; [email protected]Emmanuel FonsecaAstrophysics Science Division, Code 660.1, 8800 Greenbelt Road Goddard Space Flight Centre, Greenbelt, MD 20771, USA; [email protected]J. P. U. FynboDark Cosmology Centre, Niels Bohr Institutet, Københavns Universitet, Juliane Maries Vej 30, DK-2100 København Ø, DenmarkP. JakobssonCentre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107, IcelandE. LeitetDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, SwedenStaffan LinnéDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, SwedenPeter W. A. RomingDepartment of Astronomy & Astrophysics, Pennsylvania State University, 5252 Davey Lab, University Park, PA 16802, USAMartin StillMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking Surrey RH5 6NT, UKBing ZhangDepartment of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA

2010en

ABI

Аннотация

GRB 090417B was an unusually long burst with a T(90) duration of at least 2130 s and a multi-peaked light curve at energies of 15-150 keV. It was optically dark and has been associated with a bright star-forming galaxy at a redshift of 0.345 that is broadly similar to the Milky Way. This is one of the few cases where a host galaxy has been clearly identified for a dark gamma-ray burst (GRB) and thus an ideal candidate for studying the origin of dark bursts. We find that the dark nature of GRB 090417B cannot be explained by high redshift, incomplete observations, or unusual physics in the production of the afterglow. Assuming the standard relativistic fireball model for the afterglow we find that the optical flux is at least 2.5 mag fainter than predicted by the X-ray flux. The Swift/XRT X-ray data are consistent with the afterglow being obscured by a dense, localized sheet of dust approximately 30-80 pc from the burst along the line of sight. Our results suggest that this dust sheet imparts an extinction of A(V) greater than or similar to 12 mag, which is sufficient to explain the missing optical flux. GRB 090417B is an example of a GRBs that is dark due to the localized dust structure in its host galaxy.

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Идентификаторы

DOI: 10.1088/0004-637x/717/1/223

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