GCN Circular 58
F.E. Marshall (Goddard Space Flight Center) and T. Takeshima (USRA at GSFC) report: X-ray emission from GRB980326 was not detected during two observations with the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE). The first observation began at 05h31m UT on March 27th (about 8.2 hours after the burst) and lasted about 1850 s. The second observation began 12 days later and lasted about 1600 s. During both observations, the PCA alternated between viewing the GRB and a nearby background region. Assuming that any X-ray afterglow was negligible during the second observation and that there were no other variable sources in the field-of-view, the observed change in counting rate from the direction of the apparent optical counterpart of the GRB (IAUC 6852) of -0.03 +/- 0.15 (90% confidence) counts/sec/detector is a measure of the intensity of the X-ray afterglow 8.5 hours after the burst. An upper limit of 0.15 counts/sec/detector corresponds to a flux of 1.6e-12 ergs/s/cm**2 in the 2-10 keV band for an assumed Crab-like spectrum. This note can be cited.