Recent observations suggest that global properties of the host galaxies for long-duration γ-ray bursts (GRBs) are particularly well suited for creating the massive star progenitors of these GRBs. Motivated by the hypothesis that massive young star …
We study the chemical abundances of the interstellar medium surrounding high-z gamma-ray bursts (GRBs) through analysis of the damped Lyα systems (DLAs) identified in afterglow spectra. These GRB DLAs are characterized by large H I column densities …
Emission lines in X-ray spectra of clusters of galaxies reveal the presence of heavy elements in the diffuse hot plasma (ICM) in virial equilibrium in the dark matter potential well. Thanks to the X-ray satellites Chandra and XMM-Newton we are now …
We report the discovery and early observations of the peculiar Type IIn supernova (SN) 2006gy in NGC 1260. With a peak visual magnitude of about -22, it is the most luminous supernova ever recorded. Its very slow rise to maximum took åisebox-0.5ex 70 …
We report the results of a 944 epoch survey for transient sources with archival data from the Very Large Array spanning 22 years with a typical epoch separation of 7 days. Observations were obtained at 5 or 8.4 GHz for a single field of view and …
We report simultaneous multicolor near-infrared (NIR) observations of the supernova associated with X-ray flash 060218 during the first 16 days after the high-energy event. We find that the light curve rises and peaks relatively fast compared to …
We investigate available constraints on the circumstellar medium (CSM) around long-duration γ-ray burst (GRB) progenitors from afterglow spectra. We first establish a statistical sample of five GRB afterglow spectra that have been collected and …
Nebular-phase spectra of SN 2006aj, discovered in coincidence with XRF 060218, were obtained with Keck in 2006 July and VLT in 2006 September. At the latter epoch spectropolarimetry was also attempted, yielding a polarization upper limit of …
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 …
Starting with the first detection of an afterglow from a short-duration hard-spectrum γ-ray burst (SHB) by Swift last year, a growing body of evidence has suggested that SHBs are associated with an older and lower redshift galactic population than …