University Park, Pa. -- It didn't take long. Still in its checkout phase, the NASA-led Swift mission has detected and imaged its first gamma-ray burst, likely the birth cry of a brand new black hole.
The bright and long burst occurred on Monday, Jan. 17 and was still exploding while Swift autonomously turned to focus in less than 200 seconds. The satellite was fast enough to capture an image of the event with its X-Ray Telescope (XRT) while gamma rays were still being detected with the Burst Alert Telescope (BAT). This is the first time an X-ray telescope has imaged a gamma-ray burst while it was bursting. Most bursts are gone in about 10 seconds, and few last upwards of a minute. Previous X-ray images have captured the burst afterglow, not the burst itself.
"This is what Swift was built to do -- and nature is cooperating beautifully," said Neil Gehrels, Swift's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md. "This is the first image of prompt X-ray emission from a gamma-ray burst, and Swift's first autonomous slew caught it in the act."
"This is the one that didn't get away," said John Nousek, Swift's mission operations director at Penn State. "Swift is making its namesake proud, catching gamma-ray bursts on the fly, just like the bird it was named for. The most exciting thing is that this mission is still just revving up."
Swift is an international collaboration. The satellite, launched on Nov. 20, has three main instruments. The Burst Alert Telescope (BAT) detects the bursts and initiates the autonomous slewing to bring the XRT and the Ultraviolet/Optical Telescope (UVOT) within focus of the burst. In December the BAT started detecting bursts, including a remarkable triple detection on Dec. 19. Today's announcement marks the first BAT detection that was autonomously followed by an XRT detection, demonstrating that the satellite is slewing "swiftly," as planned. The UVOT is still being turned on and tested and was not collecting data when the burst was detected.
Scientists will need several more weeks to fully understand this burst, named GRB050117 for the date of its detection. In the days that follow, telescopes in orbit and on Earth will turn to the precise burst location provided by Swift to observe the burst afterglow and the region surrounding the burst.
"We are frantically analyzing the XRT data to understand the X-ray emission seen during the initial explosion and the very early afterglow," said David Burrows, the XRT lead at Penn State. "This is a whole new ballgame. This is the first time anyone has ever imaged in X-rays the transition of a gamma-ray burst from the brilliant flash to the fading embers."
When the UVOT is fully operational, both the XRT and UVOT will provide an in-depth observation of the gamma-ray burst and its afterglow. The burst is gone in a flash, but scientists can study the afterglow to learn about what caused the burst, much like a detective hunts for clues at a crime scene. Several of these bursts occur somewhere in the visible universe each day. No prompt X-ray emission (coincident with the gamma-ray burst) previously has been imaged because it usually takes hours to turn an X-ray telescope towards a burst. Scientists expect Swift to be fully operational by Feb. 1.
The origin of gamma-ray bursts remains a mystery. At least some appear to originate in massive star explosions. Others might be the result of merging black holes or neutron stars. Any of these scenarios likely will result in the formation of a new black hole. With each detected burst, Swift notifies the scientific community via the Gamma-ray Burst Coordinates Network (GCN). For the burst named GRB050117, the XRT and the BAT issued GCN notices within an hour after the initial trigger. Within the next few hours, four different observatories began trying to detect optical and infrared emission. Scientists at observatories around the globe -- small, university-based observatories training students, as well as world-class facilities such as Keck or the Hubble Space Telescope -- will have the option of continuing to follow the burst afterglow.
Swift, a medium-class explorer mission, is managed by NASA Goddard. Swift is a NASA mission with participation of the Italian Space Agency and the Particle Physics and Astronomy Research Council in the United Kingdom. It was built in collaboration with national laboratories, universities and international partners, including Penn State, Los Alamos National Laboratory in New Mexico, Sonoma State University in California, the University of Leicester in England; the Mullard Space Science Laboratory in Dorking, England; the Brera Observatory of the University of Milan, Italy; and the ASI Science Data Center in Rome.
More information about Swift is available on the Internet at http://swift.gsfc.nasa.gov