TITLE: GCN GRB OBSERVATION REPORT NUMBER: 704 SUBJECT: GRB980425, HST/STIS observations of the host galaxy DATE: 00/06/15 13:12:23 GMT FROM: Stephen Holland at IFA, U of Aarhus Stephen Holland, Johan Fynbo, Bjarne Thomsen (University of Aarhus), Michael Andersen (University of Oulu), Gunnlaugur Bjornsson (University of Iceland), Jens Hjorth (University of Copenhagen), Andreas Jaunsen (University of Oslo), Priya Natarajan (University of Cambridge, & Yale), and Nial Tanvir (University of Hertfordshire) We have obtained 1240 seconds of STIS images with the 50CCD (clear) aperture and 1185 seconds with the F28X50LP (long pass) aperture of the host galaxy of GRB 980425. This data was taken as part of the Survey of the Host Galaxies of Gamma-Ray Bursts (Holland et al. GCN 698) approximately 778 days after the burst. Combined images are now available at "http://www.ifa.au.dk/~hst/grb_hosts/data/index.html" and a GIF image of the host galaxy is available at "http://www.ifa.au.dk/~hst/grb_hosts/data/grb980425_colour.gif". An astrometric solution from VLT V-, R-, and I-band images (P.I., B. Libundgut) suggests that the supernova is located at X = 987 +/- 2, Y = 1064 +/- 2 on our drizzled long pass image. This is in an extended object with AB magnitudes of 26.2 +/- 0.1 in the STIS clear filter and 26.3 +/- 0.1 in the STIS long pass filter. An extrapolation of the V-band late-time light curve of SN 1998bw (McKenzie & Schaefer 1999, PASP, 111, 964) suggests that the SN remnant will have a magnitude of ~28.4 in the clear filter, which is near the detection limit of our data. The extended object has a full-width at half-maximum, in the long pass image, of 0.13 arcseconds. When the resolution limit (0.088 arcsec) is taken into account the object has a diameter of, at most, ~0.09 arcsec. For z = 0.0085, and a cosmology with H0 = 65, Omega_matter = 0.2 and Omega_lambda = 0, this corresponds to a diameter of less than ~17 pc. The colour and size of the object is consistent with it being a young star cluster. The extended object is embedded in a large extended feature (possibly an HI region) with a diameter of ~75 pc and an estimated colour of V-R ~= 0.7 +/- 0.3. A GIF image of the region containing the supernova is available at "http://www.ifa.au.dk/~hst/grb_hosts/data/grb980425cd_sfr.gif". A detailed analysis of these images is in progress (Holland et al. 2000, in preparation).