{
  "bibcode": "1999GCN...205....1A",
  "body": "C. W. Akerlof and T. A. McKay (Univ. of Michigan) report on behalf of the ROTSE\ncollaboration (Michigan/LANL/LLNL):\n\nWe observed the error box of GRB 990123 provided by the BACODINE Burst Position\nNotice dated 23-Jan-99 09:46:59 using the ROTSE-I telephoto camera array\nlocated at Los Alamos, New Mexico. The first exposure began at 9:47:18.30,\n22.18 seconds after the nominal burst trigger time. A rapidly fading object was\ndiscovered at the coordinates, RA = 231.3754, DEC = 44.7666 (J2000) which is\nwithin 1/3 of a pixel of the optical counterpart reported by Odewahn et al.\n(GCN #201). The light curve for this object is relatively complex: the\nluminosity increases by 3 magnitudes between the first and second exposures.\nEstimated magnitudes for the first six exposures are given below:\n\n        UTC     exposure     m_v\n\n    9:47:18.3    5 secs.    11.82\n    9:47:43.5    5 secs.     8.95\n    9:48:08.8    5 secs.    10.08\n    9:51:37.5   75 secs.    13.22\n    9:54:22.8   75 secs.    14.00\n    9:57:08.1   75 secs.    14.53\n\nNote that the ROTSE-I detector system uses an unfiltered broadband CCD so that\nmagnitude estimates are based on comparisons to catalog values for nearby\nstars. Sky patrol images of the same coordinates taken 133 minutes earlier\nshowed no evidence of the transient to a limit of at least two magnitudes\ndeeper. A more extensive analysis of this data will be available in the near\nfuture.\n\nThe discovery images will be posted on the ROTSE Web page at:\n   http://www.umich.edu/~rotse/gifs/grb990123/990123.gif\n\nThis message is quotable in publications.\n\n\n[GCN OP NOTE:  This archived copy has had a typo fixed.  The original version\nhad the 9:48:08.8 timestamp for the 3rd exposure go out as 9:47:08.8.]",
  "circularId": 205,
  "createdOn": 917133316000,
  "email": "akerlof@mich1.physics.lsa.umich.edu",
  "subject": "GRB990123, early optical counterpart detection",
  "submitter": "Carl Akerlof at U.Michigan  <akerlof@mich1.physics.lsa.umich.edu>",
  "eventId": "GRB 990123"
}