TITLE: GCN GRB OBSERVATION REPORT NUMBER: 872 SUBJECT: GRB 991208: HST Imaging of the Host Galaxy DATE: 00/11/01 20:05:21 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter, (STScI), P. Vreeswijk (Amsterdam), V. Sokolov (SAO RAS) and A. Casto-Tirado (IAA-Granada, INTA-Madrid) report on behalf of the larger HST GRB collaboration report: We observed the field of GRB 991208 with the HST STIS CCD on August 3, 2000, or approximately 8 months after outburst. A total exposure time of 5210s was obtained in the (50CCD) clear aperture. At the position of the burst we find a very compact galaxy with a magnitude of V= 24.6 +/- 0.15, where a conservative error bar is given due to the very wide bandpass of the filter. The full-width at half-maximum (FWHM) of the galaxy is measured as 0."095, only marginally larger than the intrinsic 0."08 of the STIS PSF. However, both curve-of-growth analysis and direct subtaction of a STIS PSF indicate that the object is indeed resolved. We estimate the intrinsic FWMH of the core of the galaxy is less than 0."06. Comparison of the HST image with ground-based images (Castro-Tirado et al., A&A submitted, see also GCN 452) shows the position of the optical transient to be offset from the center of the host by less than the 0."1 one-sigma uncertainty in the relative positions. We believe the ellipticity and position angle reported for the host by Bloom et al. (GCN 764) is due to the presence of a fainter, small object located approximagely 1" to the ESE of the host. It is not clear from the HST image whether these two objects are merely close due to a projection effect or whether they are indeed physically related. The wider (50") field of the STIS CCD shows a rich association of spiral galaxies surrounding the position of the OT. While some of the spirals show grand design or prominent bulges, and are up to 5" across, we cannot rule out the possibility that the host of the GRB (which is at a redshift of 0.7, Dodonov et al., GCN 475) is a member of this apparent group of galaxies. The images can be seen at http://www.stsci.edu/~fruchter/GRB/991208 . This GCN may be cited.