Astronomers have observed a previously unrecognized type of long-lasting gamma ray burst (GRB), according to Andrew Levan, an astronomer at the University of Warwick, in Coventry, England.
Three such bursts have been discovered between 2010 and 2012, and one of these, GRB 111209A, is of particular interest to scientists. Astronomers say the gamma ray burst in question is the longest ever observed, with a duration of approximately 25,000 seconds, or about 7 hours.
“We have observed the longest gamma ray burst in modern history, and think this event is caused by the death of a blue supergiant,” said lead researcher Bruce Gendre, who led the study while at the Italian Space Agency’s Science Data Center in Frascati, Italy. “It caused the most powerful stellar explosion in recent history, and likely since the Big Bang occurred.”
Long-duration gamma ray bursts are a type of stellar explosion that results from the collapse of supermassive stars. The explosions are some of the brightest and most powerful electromagnetic events in the universe. All GRBs emit power jets of ejecta, that propel matter in opposite directions at speeds approaching the speed of light, and the blasts emit surges of gamma rays and X-rays, producing afterglows that can be observed with optical and radio equipment.
Using NASA’s Swift telescope, the European Space Agency’s XMM-Newton satellite, and other international space telescopes, Gendre and his colleagues have been able to study GRB 111209A, since its eruption on Dec. 9, 2011. The 7-hour long burst is much longer than any previously observed.
Astronomers have traditionally recognized two types of GRBs: short and long, based on the duration of the gamma-ray signal. Short bursts last two seconds or less and are thought to represent a merger of compact objects in a binary system, with the most likely suspects being neutron stars and black holes. Long GRBs may last anywhere from several seconds to several minutes, with typical durations falling between 20 and 50 seconds. These events are thought to be associated with the collapse of a star many times the Sun’s mass and the resulting birth of a new black hole.
The astronomers discussed their findings Tuesday at the 2013 Huntsville Gamma-ray Burst Symposium in Nashville, Tennessee, a meeting sponsored in part by the University of Alabama at Huntsville and NASA’s Swift and Fermi Gamma-ray Space Telescope missions. Gendre’s findings appear in the March 20 edition of The Astrophysical Journal.