A novel explosive process is required for the γ-ray burst GRB 060614
Sharon, K.; Cenko, S. B.; Peterson, B. A.; Price, P. A.; Berger, E.; Gal-Yam, A.; Kulkarni, S. R.; Sari, R.; Schmidt, B. P.; Cucchiara, A.; Harrison, F.; Chevalier, R. A.; Brown, P. J.; Persson, S. E.; Fox, D. B.; Moon, D. -S.; McCarthy, P. J.; Ofek, E. O.; Soderberg, A. M.; Leonard, D. C.; Frail, D.; Davis, M. R.; Lewis, K. M.; Piran, T.; Penprase, B. E.; MacFadyen, A. I.
United States, Australia, Israel
Abstract
Over the past decade, our physical understanding of γ-ray bursts (GRBs) has progressed rapidly, thanks to the discovery and observation of their long-lived afterglow emission. Long-duration (>~2s) GRBs are associated with the explosive deaths of massive stars (`collapsars', ref. 1), which produce accompanying supernovae; the short-duration (<~2s) GRBs have a different origin, which has been argued to be the merger of two compact objects. Here we report optical observations of GRB 060614 (duration ~100s, ref. 10) that rule out the presence of an associated supernova. This would seem to require a new explosive process: either a massive collapsar that powers a GRB without any associated supernova, or a new type of `engine', as long-lived as the collapsar but without a massive star. We also show that the properties of the host galaxy (redshift z=0.125) distinguish it from other long-duration GRB hosts and suggest that an entirely new type of GRB progenitor may be required.