Astrophysics

The Detailed Optical Light Curve of GRB 030329

We present densely sampled BVRI light curves of the optical transient associated with the gamma-ray burst (GRB) 030329, the result of a coordinated observing campaign conducted at five observatories. Augmented with published observations of this GRB, …

Cosmological Uses of Gamma-Ray Bursts

Studies of the cosmic gamma-ray bursts (GRBs) and their host galaxies are starting to provide interesting or even unique new insights in observational cosmology. GRBs represent a new way of identifying a population of star-forming galaxies at …

Optical spectroscopy of microquasar candidates at low Galactic latitudes

We report optical spectroscopic observations of a sample of 6 low- galactic latitude microquasar candidates selected by cross- identification of X-ray and radio point source catalogs for |b$^II$ | łeq 5 °. Two objects resulted to be of clear …

Optical-Infrared ANDICAM Observations of the Transient Associated with GRB 030329

We present photometry of the transient associated with γ-burst (GRB) 030329 obtained with the Cerro Tololo Inter-American Observatory 1.3 meter telescope and the ANDICAM instrument, a dual optical/infrared imager. Without the need for light-curve …

The case for late-time optical bumps in GRB afterglows as a supernova signature

Observations of late-time optical bumps have been reported for several GRBs. The timescale for such bumps, and colors of such when available, find a natural explanation as due to associated supernovae. Ground-based and HST observations of the …

Photometry and Spectroscopy of GRB 030329 and Its Associated Supernova 2003dh: The First Two Months

We present extensive optical and infrared photometry of the afterglow of gamma-ray burst (GRB) 030329 and its associated supernova (SN) 2003dh over the first two months after detection (2003 March 30-May 29 UT). Optical spectroscopy from a variety of …

The First Two Host Galaxies of X-Ray Flashes: XRF 011030 and XRF 020427

Given the paucity of empirical constraints, the nature of the newly recognized phenomena called X-ray flashes (XRFs) has been an open question. However, with the recent detections of radio and X-ray afterglow it is finally possible to study the …

Gamma-Ray Burst Energetics and the Gamma-Ray Burst Hubble Diagram: Promises and Limitations

We present a complete sample of 29 gamma-ray bursts (GRBs) for which it has been possible to determine temporal breaks (or limits) from their afterglow light curves. We interpret these breaks within the framework of the uniform conical jet model, …

The Redshift and the Host Galaxy of GRB 980613: A Gamma-Ray Burst from a Merger-induced Starburst?

We present the optical and near-IR identification and spectroscopy of the host galaxy of gamma-ray burst GRB 980613. The burst was apparently associated with the optically (rest-frame UV) brightest component of an apparent system of at least five …

Discovery of GRB 020405 and Its Late Red Bump

We present the discovery of GRB 020405 made with the Interplanetary Network (IPN). With a duration of 60 s, the burst appears to be a typical long-duration event. We observed the 75 arcmin$^2$ IPN error region with the Mount Stromlo Observatory's 50 …