{
  "bibcode": "1999GCN...394....1S",
  "body": "Bradley E. Schaefer (Yale) reports:\n\n\"I have obtained UBVRIJHK images of the BeppoSAX 2' radius region \n(Gandolfi et al., BeppoSAX mail n. 99/23 or GCN 393) for GRB990806.  \nThese observations were made from 1999 August 7 6:57 UT to 10:53 UT (16.48\nto 20.39 hours after the burst), with a total exposure time of 5.1 hours\ndue to the simultaneous integrations in the infrared and optical.  The\ntotal integrations times are:\n\tU  -  60 min.\n\tB  -  64 min.\n\tV  -  30 min.\n\tR  -  15 min.\n\tI  -  15 min.\n\tJ  -  60 min.\n\tH  -  30 min.\n\tK  -  33 min.\nThese images were taken with the Yale 1 m telescope on Cerro Tololo with\nthe recently upgraded AndiCam IR/optical camera; which is well suited to\nobtaining UBVRIJHK of GRB optical transients within the first day or so\nafter the burst.\n\nNo variable source was identified in or near the GRB990806 region.\nComparisons were made between my V, R, and I images with the Digital Sky\nSurvey, the ESO R sky survey, and the ESO J sky survey.  This use of\nmultiple images and colors for both before and after allowed for the ready\nelimination of cosmic rays and color effects which can raise false alarms.\n(For example, my R image shows two point sources in the BeppoSAX 2' circle\nthat do not appear on the Digital Sky Survey despite the indications of\nthe magnitude; whereas my VRI images show the sources are very red and\nboth sources do appear near the threshold on the ESO R image.)  The area\nexamined was a region 10.24'X10.24' centered roughly on the BeppoSAX\nposition.  The threshold for reasonable completeness in the comparison is\nroughly R=20.5 mag.  As always, further analysis can push somewhat deeper,\nyet it is clear that any associated optical transient must be close to\nthis quoted limit if not fainter.  I will try to obtain deeper comparison\nimages tomorrow morning.\"",
  "circularId": 394,
  "createdOn": 934046261000,
  "email": "schaefer@grb2.physics.yale.edu",
  "subject": "GRB990806 UBVRIJHK observations",
  "submitter": "Brad Schaefer at Yale U  <schaefer@grb2.physics.yale.edu>",
  "eventId": "GRB 990806"
}