# Galaxies: ISM

## A detailed study of the optical attenuation of gamma-ray bursts in the Swift era

We present optical and near-infrared (NIR) photometry of 28 gamma-ray bursts (GRBs) detected by the Swift satellite and rapidly observed by the Reionization and Transients Infrared/Optical (RATIR) camera. We compare the optical flux at fiducial times …

## The host of the SN-less GRB 060505 in high resolution

The spiral host galaxy of the Swift GRB 060505 at z = 0.089 was the site of a puzzling long duration burst without an accompanying supernova. Studies of the burst environment by Thöne et al. suggested that this Gamma-ray Burst (GRB) came from the …

## GRB090426: the environment of a rest-frame 0.35-s gamma-ray burst at a redshift of 2.609

We present the discovery of an absorption-line redshift of z = 2.609 for GRB090426, establishing the first firm lower limit to a redshift for a gamma-ray burst (GRB) with an observed duration of <2s. With a rest-frame burst duration of T$_90z$ = …

## The Discovery of Vibrationally Excited H$_2$ in the Molecular Cloud Near GRB 080607

GRB 080607 has provided the first observational signatures of molecular absorption bands toward any galaxy hosting a gamma-ray burst (GRB). Despite the identification of dozens of features as belonging to various atomic and molecular (H$_2$ and CO) …

## The Interstellar Medium of Gamma-Ray Burst Host Galaxies. I. Echelle Spectra of Swift GRB Afterglows

We present optical echelle spectra of four gamma-ray burst (GRB) afterglows (GRB 050730, GRB 050820, GRB 051111, and GRB 060418) discovered during the first 1.5 yr of operation of the Swift satellite and localized by either the Swift telescope or …

## Temporal Variation in the Abundance of Excited Fe$^+$ Near a Gamma-Ray Burst Afterglow

Excited Si$^+$ and Fe$^+$ species are routinely observed in the host environment of gamma-ray burst (GRB) afterglows but are not commonly seen in other extragalactic locations. Their presence signals unusual properties in the gaseous environment of …

## GRB 050408: A Bright Gamma-Ray Burst Probing an Atypical Galactic Environment

The bright GRB 050408 was localized by HETE-2 near local midnight in the Western Hemisphere, enabling an impressive ground-based follow- up effort, as well as space-based follow-up from Swift. The Swift data from the XRT and our own optical …

## 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 …

## Multicolor Observations of the GRB 000926 Afterglow

We present multicolor light curves of the optical afterglow of gamma-ray burst (GRB) 000926. Beginning åisebox-0.5ex 1.5 days after the burst, the light curves of this GRB steepen measurably. The existence of such achromatic breaks is usually taken …