{
  "bibcode": "1999GCN...316....1P",
  "body": "G. Pietrzynski and A. Udalski (Warsaw University Observatory) report on\nbehalf of the OGLE microlensing survey team:\n\nWe monitored the optical counterpart of GRB 990510 (Vreeswijk et al.\n1999, GCN 310) starting on May 10.992 UT, 1999 with the 1.3-m Warsaw\ntelescope at the Las Campanas Observatory (Chile). In total 17 V-band,\n21 I-band frames were collected, covering about 10.25 hours. Exposure\ntime was 900 sec and 600 sec for the V and I-band frames, respectively.\nThe object is apparently variable -- its brightness faded by about 0.6\nmag in the course of the night: from 19.45. to 20.05 in the V band and\n18.50 to 19.15 in the I-band. Standard VI photometry of three, well\nseparated nearby constant stars (uncertainty +/-0.03 mag) is:\n\n         Delta X  Delta Y   \\alpha_2000  \\delta_2000     V       I\n         from GRB position\n\nStar 1     33.4\"E  43.9\"S   13:38:20.56  -80:30:31.9   15.617  14.636   \nStar 2     59.8\"W  21.0\"N   13:37:43.48  -80:29:26.7   16.203  15.161\nStar 3     16.5\"W  36.7\"N   13:38:00.82  -80:29:11.5   17.014  16.094\n\nPhotometry of the optical counterpart of GRB 990510 and light curves are\navailable from the OGLE Internet archive: \n\nhttp://www.astrouw.edu.pl/~ftp/ogle\n\n\n[GCN OP NOTE:  This circular was received at 12:42 11 May 99 UT,\nbut was not distributed due to not having a prior vetted account.]",
  "circularId": 316,
  "createdOn": 926427988000,
  "email": "udalski@sirius.astrouw.edu.pl",
  "subject": "GRB990510 optical observations",
  "submitter": "Andrzej Udalski at Warsaw U. Observatory  <udalski@sirius.astrouw.edu.pl>",
  "eventId": "GRB 990510"
}