Hubble Space Telescopeand Ground‐based Optical and Ultraviolet Observations of GRB 010222

We report on Hubble Space Telescope WFPC2 optical and STIS near ultravioletMAMA observations, and ground-based optical observations of GRB010222, spanning15 hrs to 71 days. The observations are well-described by a relativisticblast-wave model with a hard electron-energy distribution, p = 1.57, and a jettransition at t_j=0.93 days. These values are slightly larger than previouslyfound as a result of a correction for the contribution from the host galaxy tothe late-time ground-based observations and the larger temporal baselineprovided by the Hubble Space Telescope observations. The host galaxy is foundto contain a very compact core (size <0.25 arcsec) which coincides with theposition of the optical transient. The STIS near ultraviolet MAMA observationsallow for an investigation of the extinction properties along the line of sightto GRB010222. We find that the far ultraviolet curvature component (c_4) israther large. In combination with the low optical extinction A_V =0.11 mag,when compared to the Hydrogen column inferred from X-ray observations, wesuggest that this is evidence for dust destruction.Comment: ApJ, in pres