A new gamma-ray burst classification scheme from GRB 060614.
Gamma-ray bursts (GRBs) are known to come in two duration classes, separated at approximately 2 s. Long-duration bursts originate from star-forming regions in galaxies, have accompanying supernovae when these are near enough to observe and are probably caused by massive-star collapsars. Recent observations 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 mergers. 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 approximately 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 supernova, 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.
Gehrels
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NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. gehrels@milkyway.gsfc.nasa.gov
Norris
J P
JP
Barthelmy
S D
SD
Granot
J
J
Kaneko
Y
Y
Kouveliotou
C
C
Markwardt
C B
CB
Mészáros
P
P
Nakar
E
E
Nousek
J A
JA
O'Brien
P T
PT
Page
M
M
Palmer
D M
DM
Parsons
A M
AM
Roming
P W A
PW
Sakamoto
T
T
Sarazin
C L
CL
Schady
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P
Stamatikos
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M
Woosley
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SE