Astrophysics

An outburst of relativistic particles from the soft γ-ray repeater SGR1900+14

Soft γ-ray repeaters (SGRs) are transient sources of high-energy photons, whose brief emissions are thought to arise from young and highly magnetized neutron stars. The exact cause of these outbursts, and the nature of the energy-loss mechanism that …

The Host Galaxy of the Gamma-Ray Burst 971214

We report on Hubble Space Telescope (HST) observations of the host galaxy of GRB 971214, taken 4 months after the burst. The redshift of the proposed host galaxy at z=3.418, combined with optical and radio observations of the burst afterglow, implies …

Spectroscopy of the Host Galaxy of the Gamma-Ray Burst 980703

We present spectroscopic observations of the host galaxy of GRB 980703. Several emission and absorption features are detected, making the redshift (z=0.966) completely unambiguous. This is only the third known redshift for a γ-ray burst (GRB) host. …

The Discovery and Broadband Follow-up of the Transient Afterglow of GRB 980703

We report on the discovery of the radio, infrared, and optical transient coincident with an X-ray transient proposed to be the afterglow of GRB 980703. At later times when the transient has faded below detection, we see an underlying galaxy with …

The Host Galaxy of GRB 970508

We present late-time imaging and spectroscopic observations of the optical transient (OT) and host galaxy of GRB 970508. Imaging observations roughly 200 and 300 days after the burst provide unambiguous evidence for the flattening of the light curve. …

Expected Characteristics of the Subclass of Supernova Gamma-Ray Bursts

The spatial and temporal coincidence of gamma-ray burst (GRB) 980425 and supernova (SN) 1998bw has prompted speculation that there exists a subclass of GRBs produced by SNe (``S-GRBs''). A physical model motivated by radio observations lead us to …

The gamma-ray burst of 980425 and its association with the extraordinary radio emission from a most unusual supernova

Supernova SN 1998bw exploded in the same direction and at the same time as the gamma-ray burst GRB 980425. Here we report radio observations of this type Ic supernova, beginning 4 days after the gamma-ray burst. At its peak the radio source is the …

Optical Follow-Up of GRB 970508

We report on the results of optical follow-up observations of the counterpart of the gamma-ray burst GRB 970508, starting 7 hr after the event. Multicolor U-, B-, V-, R$_c$-, and I$_c$-band observations were obtained during the first three …

Gamma-ray bursts from stellar remnants: probing the Universe at high redshift

A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes. Since these compact stellar remnants form from the …

Gamma-ray bursts from stellar remnants: probing the Universe at high redshift

A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes. Since these compact stellar remnants form from the …