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A case of mistaken identity? GRB 060912A and the nature of the long-short GRB divide

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posted on 24.10.2012, 09:06 by A. J. Levan, P. Jakobsson, R. Chapman, R. S. Priddey, C. Hurkett, N. R. Tanvir, E. Rol, P. T. O'Brien, J. P. Osborne, R. L. C. Starling, J. Gorosabel, P. Vreeswijk, N. Gehrels, C. Kouveliotou, D. V. Berk, K. Wiersema
We investigate the origin of the GRB 060912A, which has observational properties that make its classification as either a long or short burst ambiguous. Short-duration gamma-ray bursts (SGRBs) are thought to have typically lower energies than long-duration bursts, can be found in galaxies with populations of all ages and are likely to originate from different progenitors to the long-duration bursts. However, it has become clear that duration alone is insufficient to make a distinction between the two populations in many cases, leading to a desire to find additional discriminators of burst type. GRB 060912A had a duration of 6 s and occurred only ∼10 arcsec from a bright, low-redshift (z= 0.0936) elliptical galaxy, suggesting that this may have been the host, which would favour it being a short burst. However, our deep optical imaging and spectroscopy of the location of GRB 060912A using the Very Large Telescope (VLT) shows that GRB 060912A more likely originates in a distant star-forming galaxy at z= 0.937, and is most likely a long burst. This demonstrates the risk in identifying bright, nearby galaxies as the hosts of given gamma-ray bursts (GRBs) without further supporting evidence. Further, it implies that, in the absence of secure identifications, ‘host’ type, or more broadly discriminators that rely on galaxy redshifts, may not be good indicators of the true nature of any given GRB.

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Citation

Monthly Notices of the Royal Astronomical Society, 2007, 378 (4), pp. 1439-1446

Version

VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Publisher

Royal Astronomical Society (RAS)

issn

0035-8711

eissn

1365-2966

Copyright date

2007

Available date

24/10/2012

Publisher version

http://mnras.oxfordjournals.org/content/378/4/1439

Language

en

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