TITLE: GCN GRB OBSERVATION REPORT NUMBER: 325 SUBJECT: GRB 990510: optical observation DATE: 99/05/14 00:45:00 GMT FROM: Gabriele Ghisellini at Obs.Astro. di Brera D. Lazzati, S. Covino and G. Ghisellini, of the Observatory of Brera (Milan, Italy) report: In the 600 s VLT-FORS1 image taken at May 11.13509 with 1.2" seeing, the faint source 2.1" south of the OT of GRB990510 is completely consistent with being a pointlike object, 2.86+-0.02 mag (in the R band) fainter than the source located 3.9" north, 0.8" west of the OT. At this time the latter source and the OT had the same magnitude, R=19.10+-0.02 (assuming R=16.5 for the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7). This suggests that the faint source is not the host galaxy of the GRB. See in http://www.merate.mi.astro.it/~lazzati/GRB990510/ the original image, the image with the OT subtracted, and the residuals after having subtracted also the faint object, assuming it is a point source. This message is citeable.