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K. Hurley (UC Berkeley), T. Cline (NASA - GSFC), E. Mazets, S. Golenetskii (Ioffe Institute), N. Masetti (ITESRE), H.-S. Park (LLNL), A. Henden (USNO), A. Castro-Tirado (LAEFF), E. Berger (Caltech OVRO), D. Frail (NRAO), P. Price (Caltech), P. Vreeswijk (U. Amsterdam)
It is widely believed that there are at least two classes of gamma-ray bursts, namely the short duration (0.2 s), hard-spectrum bursts, and the longer duration (20 s), softer spectrum events. All the GRB counterparts observed to date, however, and all the redshifts known, are for the latter class. The 3rd Interplanetary Network has produced rapid (15-65 h), precise (11-110 square arcminutes) localizations of four short, hard bursts (GRB000607, 000125, 001204, and 010119). Radio and optical follow-up observations took place which were sensitive enough to detect counterparts to these events, if their counterparts were like those of the long, soft class. However, no counterparts were in fact detected. We discuss these observations and speculate about the reasons why the short, hard bursts might be "dark" bursts.