Past studies of cosmological γ-ray bursts (GRBs) have been hampered by their extreme distances, resulting in faint afterglows. A nearby GRB could potentially shed much light on the origin of these events, but GRBs with a redshift z ≤ 0.2 have been estimated to occur only rarely, about once per decade. Here we report the discovery of the bright optical afterglow emission from the burst of 29 March 2003 (GRB030329; ref. 2). The brightness of the afterglow and the prompt report of its position resulted in extensive follow-up observations at many wavelengths, along with the measurement of the redshift, z = 0.169 (ref. 4). The γ-ray and afterglow properties of GRB030329 are similar to those of GRBs at cosmological redshifts. Observations have already identified the progenitor as a massive star that exploded as a supernova.
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Acknowledgements This work is supported partly by a grant-in-aid from the Japanese Ministry of Education, Culture, Sports, Science and Technology. Part of this work is supported by a Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists (M.U. and R.I.).
Acknowledgements P.A.P. and B.P.S. thank the ARC for supporting Australian GRB research. GRB research at Caltech is supported in part by funds from NSF and NASA. We are indebted to S. Barthelmy and the GCN, as well as the HETE-II team for prompt alerts of GRB localizations.