{
  "bibcode": "1999GCN...402....1H",
  "body": "J. Kemp & J. Halpern (Columbia U.) report on behalf of the\nMDM Observatory GRB follow-up team's southern extension:\n\n\"We observed the optical counterpart of GRB 990712 in the R band \non Aug. 16.32 UT using the CTIO 0.9m.  A total of 50 minutes exposure\nwas obtained in seeing of 2.\"0.  An object of R = 21.73 +/- 0.06 is\ndetected at position (J2000) RA 22:31:53.00, Dec -73:24:28.7 in the \nUSNO-A2.0 reference system, with uncertainty of 0\".4.  This is consistent\nwith the OT position as measured by Bakos et al. (GCN #387) and \nHjorth et al. (GCN #389).  The magnitude is referenced to the secondary \nstandards used by Bakos et al. (IAUC #7225), although our own calibration\nusing Landolt standards (cf. GCN #395) is about 0.08 mag brighter.\nThe object appears only marginally extended in these images of relatively\npoor seeing.  Revising the decay model of Hjorth et al. (GCN #389), we\nfind a slope of -1.05 and a constant contribution of R = 21.78 from the\nhost galaxy.  An extrapolation of the OT decay with a slope of -1.05 would\nhave predicted R = 25.5 at this time. In this model, the observed light is\nnow dominated by the host galaxy.  HST observations are needed to follow \nthe afterglow decay, and to locate it within its relatively low-redshift \nhost galaxy (z=0.43, Galama et al. GCN #388).  An HST observation is \nscheduled for Aug. 29.  If the OT decay continues with a slope of -1.05,\nit will be found at R = 25.9 on Aug. 29.\n\nThe CTIO image and revised decay curve are posted at \nhttp://www.astro.bio2.edu/grb/\n\nThis message may be cited.\"",
  "circularId": 402,
  "createdOn": 934837392000,
  "email": "jules@astro.columbia.edu",
  "subject": "GRB 990712, Optical Observation",
  "submitter": "Jules Halpern at Columbia U.  <jules@astro.columbia.edu>",
  "eventId": "GRB 990712"
}