Hubble Space Telescope and Ground-based Optical and Ultraviolet Observations of GRB 010222

Abstract

We report on Hubble Space Telescope (HST) Wide Field Planetary Camera 2 optical and Space Telescope Imaging Spectrograph (STIS) near-ultraviolet MAMA observations and ground-based optical observations of GRB 010222, spanning 15 hr to 71 days. The observations are well described by a relativistic blast wave model with a hard electron energy distribution, p = 1.57^(+0.04)_(-0.03), and a jet transition at t* = 0.93^(+0.15)_(-0.06) days. These values are slightly larger than previously found as a result of a correction for the contribution from the host galaxy to the late-time ground-based observations and the larger temporal baseline provided by the HST observations. The host galaxy is found to contain a very compact core (size <0 25), which coincides with the position of the optical transient. The STIS near-ultraviolet MAMA observations allow for an investigation of the extinction properties along the line of sight to GRB 010222. We find that the far-ultraviolet curvature component c4 is rather large. In combination with the low optical extinction, AV = 0.110^(+0.010)_(-0.021) mag, when compared with the hydrogen column inferred from X-ray observations, we suggest that this is evidence for dust destruction.

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