{
  "bibcode": "1999GCN...313....1G",
  "body": "T.J. Galama, P.M. Vreeswijk, E. Rol (U. of Amsterdam), N. Tanvir\n(Institute of Astronomy, Cambridge, UK), E. Palazzi, E. Pian,\nN. Masetti, F. Frontera (ITESRE, CNR, Bologna), K. Pollard (U. of\nCanterbury), J. Menzies (SAAO), P. Sackett (U. of Groningen), K. Sahu\n(STScI), J. van Paradijs (U. of Amsterdam and U. of Alabama in\nHuntsville), and C. Kouveliotou (USRA/MSFC) report on behalf of the\nPLANET microlensing team, and the Bologna and Amsterdam/Huntsville GRB\noptical follow-up teams:\n\nComparison of European Southern Observatory 2.2m and SAAO Sutherland\n1.0m telescope (South Africa) R-band observations, of the error box of\nGRB 990510 (Dadina et al. 1999; IAU Circular 7160), shows that the\nproposed optical counterpart to GRB 990510 (Vreeswijk et al., GCN\n#310) is decaying in brightness. We obtain the following magnitudes\n(measured with respect to the USNO star at RA = 13:38:00.82, \nDEC=-80:29:11.7, for which we have assumed R = 17.2):\n\n\tR mag\t  err\tMay (UT)   Telescope\t\n\n\t19.11    0.02    10.73\t   SAAO 1m\n\t19.17    0.02    10.76\t   SAAO 1m\n\t19.25    0.02    10.79     SAAO 1m\n \t19.61    0.01    10.99     ESO 2.2m\n\nThe absolute uncertainty in the calibration is not included. The decay\nis consistent with a power law, with temporal decay index -0.85 +- 0.04.\n\nThe light curve can be found at http://www.astro.uva.nl/~titus/grb990510.html\n\nThis message is citeable.",
  "circularId": 313,
  "createdOn": 926388939000,
  "email": "titus@astro.uva.nl",
  "subject": "GRB 990510 optical observations",
  "submitter": "Titus Galama at U.Amsterdam  <titus@astro.uva.nl>",
  "eventId": "GRB 990510"
}