0000000001037540
AUTHOR
Paolo A. Mazzali
Off-Axis Properties of Short Gamma-Ray Bursts
Based on recent models of relativistic jet formation by thermal energy deposition around black hole-torus systems, the relation between the on- and off-axis appearance of short, hard gamma-ray bursts (GRBs) is discussed in terms of energetics, duration, average Lorentz factor, and probability of observation, assuming that the central engines are remnants of binary neutron star or neutron star-black hole mergers. As a consequence of the interaction with the torus matter at the jet basis and the subsequent expansion of the jets into an extremely low-density environment, the collimated ultrarelativistic outflows possess flat core profiles with only little variation of radially-averaged propert…
A tale of two GRB-SNe at a common redshift of z=0.54
We present ground-based and HST optical observations of the optical transients (OTs) of long-duration Gamma Ray Bursts (GRBs) 060729 and 090618, both at a redshift of z = 0.54. For GRB 060729, bumps are seen in the optical light curves (LCs), and the late-time broadband spectral energy distributions (SEDs) of the OT resemble those of local type Ic supernovae (SNe). For GRB 090618, the dense sampling of our optical observations has allowed us to detect well-defined bumps in the optical LCs, as well as a change in colour, that are indicative of light coming from a core-collapse SN. The accompanying SNe for both events are individually compared with SN1998bw, a known GRB-supernova, and SN1994I…