Gamma Rays

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 …

Is the Redshift Clustering of Long-Duration Gamma-Ray Bursts Significant?

The 26 long-duration gamma-ray bursts (GRBs) with known redshifts form a distinct cosmological set, selected differently than other cosmological probes such as quasars and galaxies. Since the progenitors are now believed to be connected with active …

The Redshift Determination of GRB 990506 and GRB 000418 with the Echellete Spectrograph Imager on Keck

Using the Echellete Spectrograph Imager (ESI) on the Keck II 10 m telescope we have measured the redshifts of the host galaxies of gamma-ray bursts GRB 990506 and GRB 000418, z=1.30658+/-0.00004 and 1.1181+/-0.0001, respectively. Thanks to the …

The Observed Offset Distribution of Gamma-Ray Bursts from Their Host Galaxies: A Robust Clue to the Nature of the Progenitors

We present a comprehensive study to measure the locations of gamma-ray bursts (GRBs) relative to their host galaxies. In total, we find the offsets of 20 long-duration GRBs from their apparent host galaxy centers by utilizing ground-based images from …

The Prompt Energy Release of Gamma-Ray Bursts using a Cosmological k-Correction

The fluences of gamma-ray bursts (GRBs) are measured with a variety of instruments in different detector energy ranges. A detailed comparison of the implied energy releases of the GRB sample requires then an accurate accounting of this diversity in …

The host to gamma-ray burst 970508: a distant dwarf galaxy?

If the optical transient to gamma-ray burst (GRB) 970508 is indeed associated with the 8 May burst and is connected with the z = 0.835 absorption system reported by Metzger et al. (1997) [Natur, 387, 879], then either the GRB originated from an …

The decay of optical emission from the γ-ray burst GRB 970228.

The optical counterpart of the γ-ray burst GRB 970228 appears to be a transient point source embedded in a region of extended nebulosity, the latter having been tentatively identified as a high-redshift galaxy. This would seem to favour models that …