Journal Article

An enigmatic long-lasting γ-ray burst not accompanied by a bright supernova

Mangano, V., Tagliaferri, G., Mirabel, I. F., Covino, S., Valle, M. Della, Testa, V., Panagia, N., Campana, S., Fugazza, D., Malesani, D., D’Avanzo, P., Stella, L., Piranomonte, S., Chincarini, G., Pellizza, L. J., Antonelli, L. A., Hurley, K.

2006

Overview

The long and the short of it The tidy classification system that divided γ-ray bursts (GRBs) into long-duration busts (lasting more than two seconds) and short may have had its day. The final nail in its coffin may be GRB 060614. Discovered on 14 June 2006 by the Burst Alert Telescope on-board the Swift satellite, this burst was long, at 102 seconds, but as reported in a clutch of papers in this issue, it has a number of properties, including the absence of an accompanying supernova, that were previously considered diagnostic of a 'short' GRB. The hunt is now on for a classification system to take account of the diversity now apparent in GRBs. In the accompanying News & Views, Bing Zhang suggests that the answer may be to adopt a Type I/Type II classification similar to that used for supernovae. Deep optical observations of GRB 060614 show no emerging supernova with absolute magnitude brighter than M V = − 13.7. Any supernova associated with GRB 060614 was therefore at least 100 times fainter, at optical wavelengths, than the other supernovae associated with GRBs. Gamma-ray bursts (GRBs) are short, intense flashes of soft γ-rays coming from the distant Universe. Long-duration GRBs (those lasting more than ∼2 s) are believed to originate from the deaths of massive stars 1 , mainly on the basis of a handful of solid associations between GRBs and supernovae 2 , 3 , 4 , 5 , 6 , 7 . GRB 060614, one of the closest GRBs discovered, consisted of a 5-s hard spike followed by softer, brighter emission that lasted for ∼100 s (refs 8 , 9 ). Here we report deep optical observations of GRB 060614 showing no emerging supernova with absolute visual magnitude brighter than M V  = -13.7. Any supernova associated with GRB 060614 was therefore at least 100 times fainter, at optical wavelengths, than the other supernovae associated with GRBs 10 . This demonstrates that some long-lasting GRBs can either be associated with a very faint supernova or produced by different phenomena.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Astronomy / Earth, ocean, space / Exact sciences and technology / Gamma-ray sources ; gamma-ray bursts / Humanities and Social Sciences / letter / multidisciplinary / Science / Science (multidisciplinary) / Stellar systems. Galactic and extragalactic objects and systems. The universe / Unidentified sources and radiation outside the solar system