Meanwhile the other telescopes on Swift continued to observe the unusually long-lived burst; it lasted more than 30 minutes compared with other examples that flared up for only milliseconds. As the x-rays faded away, the star itself exploded in a spectacular supernova--shown in the before (l) and after (r) images above--the first such supernova to be observed from start to finish. Several teams of astronomers report their findings in a series of papers in today's Nature.
Beyond the novelty of the event, astronomers noted some unusual characteristics. Alicia Soderberg of the California Institute of Technology and her team used NASA's Chandra X-ray Observatory to determine that the initial beacon was an x-ray flash rather than a more typical kind of gamma-ray burst. Elena Pian of the Osservatorio Astronomico di Trieste in Italy and her team used the Very Large Telescope in Chile to link the burst and the subsequent supernova as well as to determine that this supernova was half as bright as those typically preceded by such a burst, despite its emanating from a star 20 times as massive as the sun. Such details led Paolo Mazzali of the Max Planck Institute for Astrophysics in Garching, Germany, to speculate that the series of events might be driven by the birth of a magnetized neutron star, or magnetar.
Because such events are dimmer by nature than previously observed gamma-ray bursts, they are much harder to detect, and only the speedy work of Swift and the explosion's relative nearness allowed astronomers to study it. Nevertheless, such events are probably more common than their more powerful cousins, astronomers say. "Usually these events are not detected until after the supernova has brightened substantially," says Keith Mason of the Particle Physics and Astronomy Research Council in Swindon, England. "On this occasion, we were able to study the remarkable event in all its glory from the very beginning."