Localizations of 13 gamma-ray bursts by the All-Sky Monitor on the Rossi X-ray Timing Explorer

The All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE) has bee n used to localize 13 confirmed X-ray counterparts to gamma-ray bursts (GRB s) detected over 3 yr of operation. We quantify the errors in ASM localizat ions of brief transient sources by using observations of persistent sources with well-known locations. We apply the results of this analysis to obtain accurate error boxes with reliable confidence levels for the 13 GRBs. In s ix of these 13 cases, multiple detections by the ASM allow the positions to be localized to a diamond of order similar to 15' x 3', In five further ca ses, the Interplanetary Network (IPN) constrains the usually similar to 3 d egrees x 3' (full-width) ASM error box to an area of a few tens of square a rcminutes. This work adds 11 burst localizations to the list of similar to 60 well-localized GRBs.