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A new γ-ray burst classification scheme from GRB 060614


Gamma-ray bursts (GRBs) are known to come in two duration classes1, separated at 2 s. Long-duration bursts originate from star-forming regions in galaxies2, have accompanying supernovae when these are near enough to observe and are probably caused by massive-star collapsars3. Recent observations4,5,6,7,8,9,10 show that short-duration bursts originate in regions within their host galaxies that have lower star-formation rates, consistent with binary neutron star or neutron star–black hole mergers11,12. Moreover, although their hosts are predominantly nearby galaxies, no supernovae have been so far associated with short-duration GRBs. Here we report that the bright, nearby GRB 060614 does not fit into either class. Its 102-s duration groups it with long-duration GRBs, while its temporal lag and peak luminosity fall entirely within the short-duration GRB subclass. Moreover, very deep optical observations exclude an accompanying supernova13,14,15, similar to short-duration GRBs. This combination of a long-duration event without an accompanying supernova poses a challenge to both the collapsar and the merging-neutron-star interpretations and opens the door to a new GRB classification scheme that straddles both long- and short-duration bursts.

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Figure 1: The light curve of GRB 060614 as observed with the BAT.
Figure 2: Spectral lag as a function of peak luminosity showing GRB 060614 in the region of short-duration GRBs.

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Correspondence to N. Gehrels.

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Gehrels, N., Norris, J., Barthelmy, S. et al. A new γ-ray burst classification scheme from GRB 060614. Nature 444, 1044–1046 (2006).

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