TITLE: GCN GRB OBSERVATION REPORT NUMBER: 565 SUBJECT: HST Observations of GRB 990712 DATE: 00/02/24 20:51:00 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter, K. Sahu, R. Gibbons, L. Petro and H. Ferguson (STScI) on behalf of the larger HST GRB collaboration report: We have observed the field of GRB 990712 with the HST STIS CCD on August 29, 1999, 48 days after outburst. Observations with total exposures times of 3720s were taken in both the (50CCD) clear aperture and (LP) long pass filters. At the position of the previously located OT (GCN reports starting with GCN 387), we find a disk galaxy with two apparent knots along its major axis. Using the astrometry of Sahu et al. (2000, Ap J. accepted) we are able to place the position of the OT on our image to a one-sigma accuracy no better than 0."15, where the source of the error is nearly equally divided between that of the plate solution in Sahu et al.'s original image and the measurement of the relative position of the OT to the astrometric calibrators in that image. The best estimate position of the OT is offset from the fainter blue knot by only 0."07; however, a brighter red knot lying 0."24 from the best estimate position can not be ruled out as the true location of the OT. The images are displayed at http://www.stsci.edu/~fruchter/GRB/990712 . These results are being published now because comments from members of the community have made it clear that there is great interest even in inconclusive HST results. However, this object is scheduled to be reobserved in late April or early May of this year. The resulting images, when subtracted from those reported here, should allow an unambiguous identification of the OT, and an accurate determination of its magnitude and color at this first HST epoch.