spacetoday.net: Astronomers conclusively link gamma-ray bursts to supernovae

Posted: Tue, Jun 24, 2003, 11:00 AM ET (1500 GMT)
GRB and hypernova illustration (Harvard Smithsonian CfA)

Astronomers announced last week that they have the strongest evidence to date linking gamma-ray bursts with the most powerful class of supernova explosions. In a paper published in the journal Nature, an international team of astronomers reported on observations of a gamma-ray burst (GRB) detected on March 29 of this year. A bright "optical afterglow" associated with the GRB was seen at visible wavelengths just 90 minutes after the GRB was first detected; that afterglow was monitored by astronomers for weeks after the burst. Spectra taken of the afterglow show that it is very similar to spectra taken of "hypernovae", a class of extremely powerful supernova explosions. Comparing the hypernova observations with those from previous events, astronomers concluded that the hypernova took place within two days of the GRB, leading astronomers to conclude that the hypernova and the GRB are conclusively linked. Astronomers also believe the observations support a theoretical explanation for hypernovae and GRBs called the "collapsar" model, which explains the phenomena through the instantaneous, non-symmetrical collapse of the core of a large star.