Gamma-Ray Burst associated Supernovae: Outliers become Mainstream
Abstract
During the last eight years a clear connection has been established between the two most powerful explosions in our Universe: core-collapse supernovae (SNe) and long gamma ray bursts (GRBs). Theory suggests that every GRB is simultaneously accompanied by a SN, but in only a few nearby cases have these two phenomena been observed together. We report the discovery and daily monitoring of SN2006aj associated with the GRB060218. Because the event was the second closest GRB, both explosions could be examined in detail. GRB060218 had an unusually soft spectrum, long duration, and a total energy 100 to 1000 times less than most other GRBs. Yet SN2006aj was similar to those in other GRBs, aside from rising more rapidly and being ~40% fainter. Taken together, these observations suggest that GRBs have two components: a broad, energetic, but only mildly relativistic outflow that makes a SN, and a more narrowly focused, highly relativistic jet responsible for the GRB. The properties of the GRB jet apparently vary greatly from event to event, while the broad SN outflow varies much less. Low energy transients like GRB060218 may be the most common events in the Universe.Keywords
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