May 6, 2013
NASA Telescopes Observe Brightest Gamma-Ray Burst Ever Detected
John P. Millis, Ph.D. for redOrbit.com — Your Universe Online
On Saturday, April 27, the Fermi Gamma-ray Telescope detected a sudden, powerful flux of high-energy gamma-rays, indicating a historic burst event in a distant galaxy. The instrument then notified other telescopes located in space and on the ground that a Gamma-ray Burst (GRB) had been detected.
Fermi´s main instrument the Large Area Telescope (LAT) detected gamma-rays as high as 94 giga-electron volts (GeV), nearly three times the maximum energy ever detected by a burst.
GRB events of various types are detected a few times a week on average, but are rarely found to be this bright or energetic. Also unique to this particular event was that the emission continued for nearly a day, easily besting the duration record for such an event. The event lasted long enough that many other observatories, including the Swift satellite, were able to monitor the source.
"We have waited a long time for a gamma-ray burst this shockingly, eye-wateringly bright," according to Julie McEnery, project scientist for the Fermi Gamma-ray Space Telescope at NASA's Goddard Space Flight Center in Greenbelt, Md. "The GRB lasted so long that a record number of telescopes on the ground were able to catch it while space-based observations were still ongoing."
The rapid production of high-energy gamma-rays by the GRB likely resulted from the collapse from a very massive star, some tens or possibly hundreds of times the mass of our Sun, and will continue to evolve much like a standard supernova. As the core collapses into a dense black hole, the jets, beamed by the powerful magnetic fields, drives matter into the surrounding medium.
The initial afterglow, created as the matter in the jets interacts with matter surrounding the star, can last for months in various wavelengths. The shockwaves from the explosion can ignite the surrounding medium and create a brilliant nebula that can persist for hundreds of thousands of years and expand over light-years of space.
The next task is to continue monitoring the source region and search for an expanding supernova remnant, and the massive black hole that is sure to lurk within.
Since this event occurred some 3.6 billion light-years from Earth, which is relatively close for a GRB, we have a great opportunity to learn more about the most powerful explosions in the Universe. "This GRB is in the closest 5 percent of bursts, so the big push now is to find an emerging supernova, which accompanies nearly all long GRBs at this distance," said Neil Gehrels, principal investigator for the Swift experiment.