GAMMA-RAY BURST ARRIVAL TIME LOCALIZATIONS - SIMULTANEOUS OBSERVATIONS BY PIONEER-VENUS-ORBITER, COMPTON-GAMMA-RAY-OBSERVATORY, AND ULYSSES

Between the Compton Gamma Ray Observatory (CGRO) launch in 1991 April and the Pioneer Venus Orbiter (PVO) demise in 1992 October, concurrent coverage by CGRO, PVO, and Ulysses was obtained for several hundred g amma-ray bursts (GRBs). Although most of these were below the PVO and UIysses thresholds, 37 were positively detected by all three spacecraf t, with data quality adequate for quantitative localization analysis. All were localized independently to similar to 2 degrees accuracy by t he CGRO Burst and Transient Source Experiment (BATSE), and three were also localized by COMPTEL. we computed arrival-time error boxes, whose larger dimensions range from about 2' to several degrees and whose sm aller dimensions are in the arcminute range. Twelve have areas less th an 10 arcmin(2), and only four have areas greater than 1 deg(2). The a rea of the smallest box is 0.44 arcmin(2). We find that the overall BA TSE localization accuracy for these events is consistent with the most recent stated uncertainties. This work indicates that the ROSAT soft X-ray source found within a preliminary IPN error box for GB920501 (Tr ig 1576) (Hurley et al.) is less likely to be the GRB counterpart than previously reported.