The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connection

Creators: Bloom, J. S.; Kulkarni, S. R.; Djorgovski, S. G.; Eichelberger, A. C.; Côté, P.; Blakeslee, J. P.; Odewahn, S. C.; Harrison, F. A.; Frail, D. A.; Filippenko, A. V.; Leonard, D. C.; Riess, A. G.; Spinrad, H.; Stern, D.; Bunker, A.; Dey, A.; Grossan, B.; Perlmutter, S.; Knop, R. A.; Hook, I. M.; Feroci, M.

Abstract

Cosmic γ-ray bursts have now been firmly established as one of the most powerful phenomena in the Universe, releasing almost the rest-mass energy of a neutron star within the space of a few seconds (ref. 1). The two most popular models to explain γ-ray bursts are the coalescence of two compact objects such as neutron stars or black holes, or the catastrophic collapse of a massive star in a very energetic supernova-like explosion. Here we show that, about three weeks after the gamma-ray burst of 26 March 1998, the transient optical source associated with the burst brightened to about 60 times the expected flux, based upon an extrapolation of the initial light curve. Moreover, the spectrum changed dramatically, with the colour becoming extremely red. We argue that the new source is an underlying supernova. If our hypothesis is true then this provides evidence linking cosmologically located γ-ray bursts with deaths of massive stars.

Additional Information

© 1999 Macmillan Magazines Ltd. Received 25 May; accepted 22 July 1999. We thank M. H. van Kerkwijk and S. A. Stanford for observations at the Keck II telescope and R. Sari for discussions. We also acknowledge the support from the staff at the Keck Observatory. The observations reported here were obtained at the W. M. Keck Observatory, made possible by the financial support of the W. M. Keck Foundation, which is operated by the California Association for Research in Astronomy, a scientific partnership among California Institute of Technology, the University of California and NASA. S.R.K. and A.V.F. were supported by the NSF and NASA. S.G.D. acknowledges partial support from the Bressler Foundation.

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The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connection

Abstract

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