Published online by Cambridge University Press: 12 April 2016
The mystery of the nature and origin of gamma-ray bursts (GRBs) has persisted over two decades of intensive research, observational and theoretical. The basic problem is the absence of quiescent or transient counterparts at other wavelengths, resulting in distance scale uncertainties of more than 10 orders of magnitude. Searches for counterparts are hampered by the lack of sufficiently accurate localizations and by a lack of criteria that uniquely identify the expected appearance of counterparts (although see Meszaros &: Rees 1993, Meszaros et al. 1994). The detection of archival optical transients (OT’s) inside γ-ray burst error boxes suggested burst recurrence and generated hope for a breakthrough in the γ-ray burst counterpart search (e.g., Schaefer 1990). However, counterparts of these OT’s have never been identified, and the reality of several archival images was questioned (Zytkow 1990, but see Schaefer 1990). The search for multi-wavelengths transients has recently been extended to neutrino- and gravitational wave emission. The status of multiwavelength surveys for quiescent or transient counterparts prior to 1988 was reviewed by Hartmann & Woosley (1988). Here we update that review and discuss “optical” emission in view of the current debate on the burster distance scale. Other recent reviews are by Schaefer (1994) and Greiner (1995).