The Unusually Long Duration Gamma‐Ray Burst GRB 000911: Discovery of the Afterglow and Host Galaxy

Of all the well localized gamma-ray bursts, GRB 000911 has the longestduration (T_90 ~ 500 s), and ranks in the top 1% of BATSE bursts for fluence.Here, we report the discovery of the afterglow of this unique burst. In orderto simultaneously fit our radio and optical observations, we are required toinvoke a model involving an hard electron distribution, p ~ 1.5 and a jet-breaktime less than 1.5 day. A spectrum of the host galaxy taken 111 days after theburst reveals a single emission line, interpreted as [OII] at a redshift z =1.0585, and a continuum break which we interpret as the Balmer limit at thisredshift. Despite the long T_90, the afterglow of GRB 000911 is not unusual inany other way when compared to the set of afterglows studied to date. Weconclude that the duration of the GRB plays little part in determining thephysics of the afterglow.Comment: 14 pages, 7 figures. Submitted to Ap