{
  "bibcode": "1999GCN...389....1H",
  "body": "GRB 990712 Optical Decay: Indication of Bright Host Galaxy\n\nJ. Hjorth (University of Copenhagen) and F. Courbin, J. Cuadra, D. Minniti \n(Universidad Catolica de Chile) report:\n\n\n\"We have obtained a 5-min R-band exposure of the optical afterglow of\nGRB 990712 (Frontera, GCN #385; Bakos et al., GCN #387) with the\nESO 3.5-m NTT on 16.403 July 1999 UT. We detect an unresolved (seeing\nFWHM = 1.8\") object at RA (2000) = 22 31 53.03, Dec (2000) = -73 24 28.3\n(with a positional uncertainty of +- 0.6\" relative to the USNO-A2.0 system),\nconsistent with the position of the bright decaying source discovered by\nBakos et al. (IAUC 7225). We have tied our photometry to the PLANET\nphotometric zeropoint (K. Sahu, personal communication) and find that the\nobject has continued to fade to R = 21.48 +- 0.02 (systematic) +- 0.05\n(random). The combined SAAO data (Bakos et al., IAUC 7225) and NTT data\nindicate that the light curve is leveling off relative to a power law\ndecline. Assuming that the light curve can be modeled as the combined effects\nof a power law decline of the OT and a constant contribution from the host\ngalaxy we find an OT decay slope of -0.81 (i.e. a rather slow decay) and a\nbright host galaxy with R = 22.0. Such a bright host galaxy would be\nconsistent with its fairly low redshift (z = 0.43) and would possibly even\naccount for the prominent emission lines seen in the VLT spectrum\n(Galama et al., GCN #388). We caution however that the hypothesis of a bright\nhost galaxy is based on just a few data points. To test this hypothesis\ncontinued monitoring of the system is therefore urged. The NTT image and the\nR-band light curve are posted at http://www.astro.ku.dk/~jens/grb990712/ .\"",
  "circularId": 389,
  "createdOn": 932236576000,
  "email": "jens@astro.ku.dk",
  "subject": "GRB 990712 Optical Decay: Indication of Bright Host Galaxy",
  "submitter": "Jens Hjorth at U.Copenhagen  <jens@astro.ku.dk>",
  "eventId": "GRB 990712"
}