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Session 119 - Gamma Ray Bursts.
Oral session, Saturday, January 10
International Ballroom Center,
The All-Sky Monitor (ASM) on RXTE can provide useful scientific data to the community for the investigation of gamma-ray bursts (GRBs). We are developing two complementary methods by which the ASM searches for the X-ray counterparts to gamma-ray bursts: we determine whether or not a BATSE location as delivered through the Gamma-ray burst Coordinate Network (GCN) is scanned by the ASM at or shortly after the BATSE trigger, and (2) we search for transient events in ASM time-series data that correspond to new sources in ASM position histogram data. If a GRB is detected in one ASM camera, a position can be determined to within a box of dimensions a few degrees by a few arcminutes. Multiple-camera detections, or comparison with other instruments in the Interplanetary Network (IPN), can constrain this position to a few arcminutes. In its first eighteen months, the ASM has detected twelve GRB candidates. Four of these were also detected by BATSE and Ulysses, and a further two by Konus and Ulysses, enabling a triangulation annulus to be computed from the IPN to confirm and constrain the location. Four further events were detected by one other mission (BATSE, Konus, or Ulysses), which confirms the GRB nature of the events, but does not enable the position to be constrained any better than the long, thin ASM one-camera error box. All ASM positions will be made available through the GCN as soon as possible: we estimate between 15 and 60 minutes.
