Hubble Space TelescopeSTIS Observations of GRB 000301C: CCD Imaging and Near‐Ultraviolet MAMA Spectroscopy

Abstract

We present Space Telescope Imaging Spectrograph observations of the optical transient (OT) counterpart of the gamma-ray burster GRB 000301C obtained 5 days after the burst, on 2000 March 6. CCD clear-aperture imaging reveals a R~=21.50+/-0.15 source with no apparent host galaxy. An 8000 s, 1150 A 18 on the line of sight to the OT. This measured redshift is conservatively a lower limit to the GRB redshift. However, as all other GRBs that have deep Hubble Space Telescope images appear to lie on the stellar field of a host galaxy, and as the large H I column density measured here and in later ground-based observations is unlikely on a random line of sight, we believe we are probably seeing absorption from H I in the host galaxy. In any case, this represents the largest direct redshift determination of a gamma-ray burster to date. Our data are compatible with an OT spectrum represented by a power law with an intrinsic index alpha=1.2 (fnu~nu-alpha) and no extinction in the host galaxy, or with alpha=0.5 and extinction by SMC-like dust in the OT rest frame with AV=0.15. The large NHI and the lack of a detected host are similar to the situation for damped Lyalpha absorbers at z>2. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.