A New Population of High Redshift Short-Duration Gamma-Ray Bursts

Berger, E
Fox, D B
Price, P A
Nakar, E
Gal-Yam, A
Holz, D E
Schmidt, B P
Cucchiara, A
Cenko, S B
Kulkarni, S R
Soderberg, A M
Frail, D A
Penprase, B E
Rau, A
Ofek, E
Burnell, S J B
Cameron, P B
Cowie, L L
Dopita, M A
Hook, I
Peterson, B A
Podsiadlowski, P
Roth, K C
Rutledge, R E
Sheppard, S S
Songaila, A

Publication date

November 2006

Abstract

The redshift distribution of the short-duration GRBs is a crucial, but currently fragmentary, clue to the nature of their progenitors. Here we present optical observations of seven short GRBs obtained with Gemini, Magellan, and HST. We detect the afterglows and host galaxies of two short bursts, and host galaxies for two additional bursts with known optical afterglow positions, and three with X-ray positions (0.7 (97% confidence level), suggesting that 1/4-2/3 of all short GRBs originate at higher redshifts than previously determined. This has two important implications: (i) We constrain the acceptable age distributions to a wide lognormal (sigma~1) with tau~4-8 Gyr, or to a power law, P(tau)~tau^n, with -1<n<0; and (ii) the inferred isotro...