{
  "bibcode": "2003GCN..2243....1F",
  "body": "A. Fruchter (STScI), A. Levan (U. Leicester/STScI), R. Hook\n(ST-ECF/STScI), N. Pirzkal (ST-ECF), J. Gorosabel (STScI/IAA-CSIC),\nP. Garnavich (Notre Dame), P. Nugent (LBNL), S. Thorsett (UCSB),\nA. Castro-Tirado (IAA), J.M. Castro Ceron (STScI), C. Kouveliotou\n(USRA), S.T. Holland (Notre Dame), J. Hjorth (U.  Copenhagen), and\nN. Tanvir (U. Hertfordshire) report for the GOSH collaboration:\n\nGRB 030329 has been observed at three epochs by HST:  15/16 April,\n21/23 April and 12/13 May.  During all epochs UV (ACS/HRC), optical\n(ACS/WFC) and NIR (NICMOS) images were obtained.  Additionally, in\nthe first epoch an ACS grism spectrum was taken, and in the second\nepoch a STIS optical spectrum, delayed from the first epoch by a\ngyrocope failure, was also obtained.  Here we report on aspects of\nthe imaging and grism spectroscopy which provide a unique contribution\nfrom HST:  information on the nature of the host.\n\nAll the ACS images show the host extending to approximately ~0.\"5\nfrom the OT to the west, with a PA of approximately 230 degrees.\nIn the most recent ACS/WFC images the OT has faded sufficiently to\nallow a reasonable subtraction of the OT from the host, particularly\nin the F435W and F606W filters where the blue color of the host\nprovides greater contrast against the redder OT than in the F814W\nimage.   We find the magnitude of the host to be approximately\nV=22.7 +/- 0.3, where the uncertainty is dominated by the subtraction\nof the OT and the unknown contribution to the host magnitude by\nfaint outerlying areas.  This apparent magnitude corresponds to an\nabsolute magnitude of about -16.5, very similar to that of the SMC.\n\nThe host can also be seen clearly in the UV ACS/HRC F250W images\ntaken on May 12.  The OT appears to lie at the end of a bar-like\nstructure approximately 0.\"25 across, which at the ~600 Mpc\nangular-diameter distance of the GRB corresponds to a length of\nabout 800 pc.\n\nThe separation of the host from the OT can also be discerned in\nthe grism spectrum, where the emission lines of the host are seen\nto be offset from spectral continuum of the OT.   Although the\nspatial projection of the grism makes this somewhat uncertain, the\nHalpha emission of the host appears to be fairly well centered on\nhost's blue light.\n\nImages of the OT and host and the 2-d grism spectrum can be seen\nat\n\nhttp://www.stsci.edu/~fruchter/GRB/030329\n\n[GCN OPS NOTE (23may03):  The extra zero in the URL was removed.]",
  "circularId": 2243,
  "createdOn": 1053714865000,
  "email": "fruchter@stsci.edu",
  "subject": "GRB 030329:  HST ACS Observations of the Host",
  "submitter": "Andrew S. Fruchter at STScI  <fruchter@stsci.edu>",
  "eventId": "GRB 030329"
}