TY - JOUR
T1 - GRB 090417B and its Host Galaxy
T2 - A Step Toward an Understanding of Optically Dark Gamma-ray Bursts
AU - Holland...[et al.], S.T.
AU - Sbarufatti, B.
AU - Shen, RF.
AU - Schady, P.
AU - Fynbo, Johan Peter Uldall
PY - 2010/7/1
Y1 - 2010/7/1
N2 - GRB 090417B was an unusually long burst with a T 90 duration of at least 2130s and a multi-peaked light curve at energies of 15-150keV. 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 2.5mag 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 30-80pc from the burst along the line of sight. Our results suggest that this dust sheet imparts an extinction of AV ≳ 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.
AB - GRB 090417B was an unusually long burst with a T 90 duration of at least 2130s and a multi-peaked light curve at energies of 15-150keV. 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 2.5mag 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 30-80pc from the burst along the line of sight. Our results suggest that this dust sheet imparts an extinction of AV ≳ 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.
U2 - 10.1088/0004-637X/717/1/223
DO - 10.1088/0004-637X/717/1/223
M3 - Journal article
SN - 0004-637X
VL - 717
SP - 223
EP - 234
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
ER -