GAMMA RAYS: BURSTS

Keck Spectroscopy and Hubble Space Telescope Imaging of GRB 000926: Probing a Host Galaxy at z = 2.038

We present early-time Keck spectroscopic observations and late-time Hubble Space Telescope (HST) imaging of GRB 000926. The HST images show a small offset between the optical transient and a bright, compact knot in the host galaxy. Combined with the …

GRB 010921: Strong Limits on an Underlying Supernova from the Hubble Space Telescope

GRB 010921 was the first HETE-2 gamma-ray burst (GRB) to be localized via its afterglow emission. The low redshift of the host galaxy, z=0.451, prompted us to undertake intensive multicolor observations with the Hubble Space Telescope with the goal …

Optical Spectropolarimetry of the GRB 020813 Afterglow

The optical afterglow of gamma-ray burst GRB 020813 was observed for 3 hr with the LRIS spectropolarimeter at the Keck I telescope, beginning 4.7 hr after the burst was detected by the HETE-2. The spectrum reveals numerous metal absorption lines that …

Toward an Understanding of the Progenitors of Gamma-Ray Bursts

The various possibilities for the progenitors of gamma-ray bursts (GRBs) manifest in differing observable properties. Through deep spectroscopic and high-resolution imaging observations of some GRB hosts, I demonstrate that well-localized …

The Faint Optical Afterglow and Host Galaxy of GRB 020124: Implications for the Nature of Dark Gamma-Ray Bursts

We present ground-based optical observations of GRB 020124 starting 1.6 hr after the burst, as well as subsequent Very Large Array and Hubble Space Telescope (HST) observations. The optical afterglow of GRB 020124 is one of the faintest afterglows …

Time-dependent Optical Spectroscopy of GRB 010222: Clues to the Gamma-Ray Burst Environment

We present sequential optical spectra of the afterglow of GRB 010222 obtained 1 day apart using the Low-Resolution Imaging Spectrometer (LRIS) and the Echellette Spectrograph and Imager (ESI) on the Keck Telescopes. Three low-ionization absorption …

The Broadband Afterglow of GRB 980329

We present radio observations of the afterglow of the bright γ-ray burst GRB 980329 made between 1 month and several years after the burst, a reanalysis of previously published submillimeter data, and late-time optical and near- infrared (NIR) …

The Unusually Long Duration Gamma-Ray Burst GRB 000911: Discovery of the Afterglow and Host Galaxy

Of all the well-localized gamma-ray bursts, GRB 000911 has the longest duration (T$_90$=500 s) and ranks in the top 1% of BATSE bursts for fluence. Here we report the discovery of the afterglow of this unique burst. In order to simultaneously fit our …

Detection of a Supernova Signature Associated with GRB 011121

Using observations from an extensive monitoring campaign with the Hubble Space Telescope, we present the detection of an intermediate- time flux excess that is redder in color relative to the afterglow of GRB 011121, currently distinguished as the …

GRB 010921: Discovery of the First High Energy Transient Explorer Afterglow

We report the discovery of the optical and radio afterglow of GRB 010921, the first gamma-ray burst afterglow to be found from a localization by the High Energy Transient Explorer satellite. We present optical spectroscopy of the host galaxy, which …