GRB 060121: Implications of a Short/Intermediate Duration Gamma-Ray Burst at High Redshift

Research paper by A. de Ugarte Postigo, A. J. Castro-Tirado, S. Guziy, J. Gorosabel, G. Johannesson, M. A. Aloy, S. McBreen, D. Q. Lamb, N. Benitez, M. Jelinek, S. B. Pandey, D. Coe, M. D. Perez-Ramirez, F. J. Aceituno, M. Alises, et al.

Indexed on: 19 May '06Published on: 19 May '06Published in: Astrophysics


Since the discovery of the first short-hard gamma-ray burst afterglows in 2005, the handful of observed events have been found to be embedded in nearby (z < 1), bright underlying galaxies. We present multiwavelength observations of the short-duration burst GRB 060121, which is the first observed to clearly outshine its host galaxy (by a factor >10^2). A photometric redshift for this event places the progenitor at a most probable redshift of z = 4.6, with a less probable scenario of z = 1.7. In either case, GRB 060121 could be the farthermost short-duration GRB detected to date and implies an isotropic-equivalent energy release in gamma-rays comparable to that seen in long-duration bursts. We discuss the implications of the released energy on the nature of the progenitor. These results suggest that GRB 060121 may belong to a family of energetic short-duration events, lying at z > 1 and whose optical afterglows would outshine their host galaxies, unlike the first short-duration GRBs observed in 2005. The possibility of GRB 060121 being an intermediate duration burst is also discussed.