TITLE: GCN GRB OBSERVATION REPORT NUMBER: 778 SUBJECT: HST/STIS observations of the host galaxy of GRB 980329 DATE: 00/08/27 17:56:02 GMT FROM: Stephen Holland at IFA, U of Aarhus HST/STIS observations of the host galaxy of GRB 980329 Stephen Holland, Bjarne Thomsen (University of Aarhus), Jens Hjorth, Johan Fynbo (University of Copenhagen), Michael Andersen (University of Oulu), Gunnlaugur Bjornsson (University of Iceland), Andreas Jaunsen (ESO), Priya Natarajan (University of Cambridge, & Yale), and Nial Tanvir (University of Hertfordshire) We have used the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to image the host galaxy of GRB 980329. We obtained 8072 seconds of STIS/CCD images with the 50CCD (clear) aperture and 5416 seconds with the F28X50LP (long pass) aperture. This data was taken as part of the Survey of the Host Galaxies of Gamma-Ray Bursts (Holland et al., GCN 698) approximately 880 days after the burst occurred. Combined images are now available at "http://www.ifa.au.dk/~hst/grb_hosts/data/index.html". The drizzled F28X50LP image is based on two orbits worth of data, and will be updated when the data from the third orbit is available. A preliminary determination of the location of the radio transient VLA J070238.0+385044 associated with GRB 980329 (Taylor et al. 1998, ApJL, 502, L115), based on the astrometry of three USNO-A2.0 stars, is (X,Y) = (1039,1027) where the three-sigma uncertainty in the astrometric solution is 20 drizzled STIS pixels (0.5 arcsec). There is a faint, extended object at (X,Y) = (1031,999) in our drizzled 50CCD image. This object is also visible in the F28X50LP image. The object is approximately three sigma southwest of the position of the GRB, and is the best candidate for the host galaxy of GRB 980329. An image showing the location of the galaxy and the GRB is available at "http://www.ifa.au.dk/~hst/grb_hosts/data/grb980329cd.gif". The probable host galaxy has AB magnitudes, in an aperture of radius 0.25 arcsec, of CL = 28.6 +/- 0.3 and LP = 28.1 +/- 0.3. If we assume that the galaxy has a power-law spectrum then the preliminary Kron-Cousins R-band magnitude is R = 27.7 +/- 0.3. We also derived a preliminary calibration based on two stars from Rhoads et al. (GCN 157) and found R = 28.2 +/- 0.3. These results are consistent with each other, and are consistent with the host magnitude being 26.8 < R < 29, as determined by Gorosabel et al. (1999, A&A, 347, L31) from the decay of the optical light curve. The faintness of the galaxy is consistent with it having a redshift of z > 2 (Fruchter 1999, ApJ 512, L1; Lamb et al. 1999, A&AS, 138, 479), although we can not rule out z < 2 from the HST/STIS data alone.