{
  "bibcode": "2001GCN..1135....1B",
  "body": "GRB 010921: HST Detection of the Afterglow and Host Galaxy\n\nJ. S. Bloom, S. R. Kulkarni, F. A. Harrison, T. J. Galama, P. A. Price,\nS. G. Djorgovski, D. W. Fox, E. Berger, and D. A. Frail report on behalf\nthe larger Caltech-NRAO-CARA GRB Collaboration:\n\n\"We observed the field of GRB 010921 (Ricker et al., GCN #1096; Hurley et\nal., GCN #1097; Price et al., GCN #1107) on 2001 October 26-27 UT using\nthe WFPC F450W, F555W, F606W, F814W, F850LP filters on the Hubble Space\nTelescope for a total of 1200 s integration in each bandpass.  The\nobservations were conducted as part of the HST-GO Proposal #8867 (S.\nKulkarni, P.I.).\n\nAn astrometric comparison of the HST images with the Price et al.\ndiscovery image from Palomar reveals that the transient position is\nconsistent (to better than 1 sigma) with a red compact source O.41 arcsec\nto the East of the center of a galaxy. The Palomar localization is\ninconsistent (at the 3-sigma level) with the center of the galaxy (note:\nno correction has yet been made to the Palomar transient position in the\nPalomar image for the contribution of the galaxy to the centroid position;\ncorrecting for this effect would tend to push the Palomar transient\nposition further from the galaxy center).  Given that the red color of the\ncompact source is consistent with the Price et al. spectral slope and that\nthe localization is consistent, we identify this source as the afterglow\nof GRB 010921 and the galaxy (z=0.45; Djorgovski et al. #1108) as the\nhost.\"\n\nAn image of the host and the optical transient may be found at:\n\n   http://www.astro.caltech.edu/~jsb/GRB/grb010921-host-reg.ps\n\nThe 1 and 3-sigma uncertainty contours of the OT position measured from\nthe Palomar discovery images is shown.\n\nLinks to false-color images of the WFPC field and close-up images of the\nOT-host system may be found at:\n\n   http://www.astro.caltech.edu/~jsb/grb010921\n\nAnalysis of the broadband afterglow spectra is underway and more HST\nobservations are scheduled.\n\nThis message may be cited.",
  "circularId": 1135,
  "createdOn": 1005192432000,
  "email": "jsb@astro.caltech.edu",
  "subject": "GRB 010921: HST Detection of the Afterglow and Host Galaxy",
  "submitter": "Josh Bloom at CIT  <jsb@astro.caltech.edu>",
  "eventId": "GRB 010921"
}