HST Observations of the Host Galaxy of GRB970508

We report on observations of the field of GRB 970508 made in early August 1998, 454 days after outburst, with the STIS CCD camera onboard the Hubble Space Telescope. The images, taken in open filter (50CCD) mode, clearly reveal the presence of a galaxy which was obscured in earlier (June 1997) HST images by emission from the optical transient (OT). The galaxy is regular in shape: after correcting for the HST/STIS PSF, it is well-fitted by an exponential disk with a scale length of 0. ′′ 046 ± 0. ′′ 006 and an ellipticity of 0.70 ± 0.07. All observations are marginally consistent with a continuous decline in OT emission as t −1.3 beginning two days after outburst; however, we find no direct evidence in the HST image for emission from the OT, and the surface brightness profile of the galaxy is most regular if we assume that the OT emission is negligible, suggesting that the OT may have faded more rapidly at late times than is