Subaru Telescope | 20 July 2010
"Dark" GRB 080325 in a Dusty Massive Galaxy at z ~ 2A research team led by astronomers from Kyoto University, Tokyo Institute of Technology, and the National Astronomical Observatory of Japan used the Subaru Telescope to observe a dark gamma-ray burst (GRB) that provides clues for understanding the origin of dark gamma-ray bursts. Their research is a very rare case of the detection of a dark GRB's host galaxy and afterglow in the near-infrared wavelength (Fig.1). They not only found that the host galaxy of this GRB is one of the most massive GRB host galaxies but also that a local dusty environment around the GRB significantly suppresses its afterglow. The observational results suggest a high metallicity environment (one that is enriched by elements heavier than helium) around the GRB, a finding that is inconsistent with previous interpretations of GRBs, which associate their origin with a supernova explosion of a low-metallicity massive star (one that contains few elements heavier than helium) at the end of its life. This research suggests the possibility that GRBs classified as "dark" may originate from another mechanism such as the merger of binary stars.
Gamma-ray bursts (GRBs) are one of the most profound mysteries in current astronomy. Among the most energetic explosions in the universe, these bursts are bright flashes of enormous gamma rays that appear suddenly in the sky and usually last only several to a few tens of seconds. GRBs originate in distant galaxies far beyond the Milky Way. Their brief appearance and a quickly fading afterglow make them a challenge to research. The afterglow of a GRB can be observed in the X-ray, optical, and near-infrared wavelengths for several hours to several days. Since a gamma-ray detector cannot determine the position of the gamma-ray's source accurately, the discovery and/or identification of a galaxy by optical observations of its afterglow is necessary to examine where the GRB occurred and the nature of the environment around it. Adding to the complexity of understanding GRBs are "dark GRBs", which have extremely faint afterglows and/or cannot be detected in the optical band, are particularly elusive and have rarely been investigated, even though they may make up close to half of all GRBs.
- The Astrophysical Journal 719 (Aug 2010) doi: 10.1088/0004-637X/719/1/378