A portion of the HST/STIS 50CCD image of the field of GRB 000301C. The image shown here is about 10" across. The faint object to the center left of the field is the optical transient of GRB 000301c and its host galaxy. See the bottom of this page for an enlargement.
We have re-imaged the field of GRB 000301C with HST using the STIS CCD in both 50CCD (open) and LP (long-pass) mode. The observations were centered about 3.9 April 2000 UT with total exposure times of 2280s in both filters.
We detect a bright source on a fainter extended object at the position of the optical transient (OT). The position of the peak of the emission of the object agrees with that of the OT on previous HST images taken on 6 March 2000 (see GCN 602) to better than 0."01, based on astrometry relative to other objects visible in both HST images. We believe therefore we are observing continued emission from the OT of GRB 000301c, as well as from its host galaxy. One cannot give a precise magnitude for the OT without knowing a priori the surface brightness profile of the host. However, what we consider the best point source subtraction implies an OT magnitude of R=26.9; in any case, the point source is no brighter than R=26.7. The total magnitude of the OT plus host is 26.5 +/- 0.15 on 3.9 April 2000. Although no upper limit to the magnitude of the OT can truly be given without knowledge of the host, we note that R=26.9 is within 0.1 mag of the value for 3.9 April 2000 predicted by the fit to earlier R band data in Rhoads and Fruchter (astro-ph/0004057) and this provides some further confidence that our best estimate of the OT strength is not far off. If this value is used for the magnitude of the OT, then the host galaxy has a magnitude R = 27.8 +/- 0.25.
The STIS filter set only gives limited color information, however, our observations agree well with the spectral index of -0.9 reported by Halperin (GCN 585). A change to a spectral index of -3, as has been seen in the late time spectra of some other GRBs, would most likely have been detected.
An enlargement of the the HST STIS 50CCD image of the OT and host galaxy of GRB 000301c. Each pixel in this image is 0."025 across, or half the size of the original STIS pixel size. This image has been created from four separate HST exposures.