TITLE: GCN GRB OBSERVATION REPORT NUMBER: 394 SUBJECT: GRB990806 UBVRIJHK observations DATE: 99/08/07 17:17:41 GMT FROM: Brad Schaefer at Yale U Bradley E. Schaefer (Yale) reports: "I have obtained UBVRIJHK images of the BeppoSAX 2' radius region (Gandolfi et al., BeppoSAX mail n. 99/23 or GCN 393) for GRB990806. These observations were made from 1999 August 7 6:57 UT to 10:53 UT (16.48 to 20.39 hours after the burst), with a total exposure time of 5.1 hours due to the simultaneous integrations in the infrared and optical. The total integrations times are: U - 60 min. B - 64 min. V - 30 min. R - 15 min. I - 15 min. J - 60 min. H - 30 min. K - 33 min. These images were taken with the Yale 1 m telescope on Cerro Tololo with the recently upgraded AndiCam IR/optical camera; which is well suited to obtaining UBVRIJHK of GRB optical transients within the first day or so after the burst. No variable source was identified in or near the GRB990806 region. Comparisons were made between my V, R, and I images with the Digital Sky Survey, the ESO R sky survey, and the ESO J sky survey. This use of multiple images and colors for both before and after allowed for the ready elimination of cosmic rays and color effects which can raise false alarms. (For example, my R image shows two point sources in the BeppoSAX 2' circle that do not appear on the Digital Sky Survey despite the indications of the magnitude; whereas my VRI images show the sources are very red and both sources do appear near the threshold on the ESO R image.) The area examined was a region 10.24'X10.24' centered roughly on the BeppoSAX position. The threshold for reasonable completeness in the comparison is roughly R=20.5 mag. As always, further analysis can push somewhat deeper, yet it is clear that any associated optical transient must be close to this quoted limit if not fainter. I will try to obtain deeper comparison images tomorrow morning."