{
  "bibcode": "1999GCN...486....1D",
  "body": "Chris Dolan (U. Wisconsin), Ian Dell'Antonio (KPNO/Brown U.), Buell\nJannuzi (NOAO/KPNO), and James Rhoads (STScI) report on behalf of the\nKPNO GRB follow-up team:\n\n\"We report observations of the optical transient reported by Uglesich et al.\n(GCN #472) probably corresponding to the gamma-ray bright burst GRB 991216 \n(Kippen et al., GCN #463). We note that numerous independent confirming \nobservations have now been reported starting with those of Henden \net al. (GCN #473).\n\nOur observations consist of six 180 second R-band exposures taken in\ntwo groups of three with the KPNO 0.9m telescope and Mosaic camera on\nDecember 17, 1999 UT.  Photometric calibration was performed using\nobservations of Landolt stars in SA93, SA97, and SA98 over a range of\nairmasses from 1.1 to 2.0 to estimate the photometric zeropoints\n(referenced to airmass=0; the extinction coefficient was measured\nto be 0.085 mag/airmass in R for the night)\nof the images with an accuracy of about  +- 0.03 mag \n(based on uncertainties in the flatfielding). \nThis systematic uncertainty is in addition to our measurement \nuncertainty listed below.  Our reported coordinates of the \noptical transient were astrometrically calibrated to the USNO-A2 \ncatalog using approximately 6500 star positions, and should be \naccurate to better than +-0.15 arcsec.\n\nR-band observations from the KPNO 0.9m+Mosaic:\n\n RA  (J2000)    DEC        UT_start on    Exp  Mag  Error(statistical)\n                           Dec. 17, 1999\n05:09:31.29  +11:17:07.5    03:33:13     180s 18.63   0.02\n05:09:31.29  +11:17:07.5    03:38:50     180s 18.64   0.02\n05:09:31.28  +11:17:07.5    03:44:38     180s 18.64   0.07*\n05:09:31.27  +11:17:07.6    10:44:24     180s 19.25   0.03\n05:09:31.29  +11:17:07.5    10:50:06     180s 19.23   0.08*\n05:09:31.28  +11:17:07.5    10:55:49     180s 19.28   0.03\n\n* near edge of chip boundary, measurement is more uncertain.\n\nThe inferred power-law decay index is -1.2, consistent with that\nfound by Uglesich et al.\n\nHenden et al. (GCN #463) reported photometry relative to a\nstar at 05:09:39.30  +11:16:59.5 (J2000)\nIn our observations this star had a R magnitude of 15.187 +- 0.004 \n\nSimilarly, our measured R magnitudes for the stars measured by\nJha et al. (GCN #476) are:\n  RA (J2000)    DEC(J2000)   R mag\n05:09:29.799   +11:17:08.47  15.36+-0.01\n05:09:32.132   +11:17:23.75  19.45+-0.03\n\nThis message can be cited.\"",
  "circularId": 486,
  "createdOn": 945495934000,
  "email": "grb@noao.edu",
  "subject": "GRB991216, optical observations",
  "submitter": "KPNO 0.9m group at KPNO  <grb@noao.edu>",
  "eventId": "GRB 991216"
}