Gamma-ray bursts (GRBs) are the most powerful explosions the Universe has seen since the Big Bang. They occur approximately once per day and are brief, but intense, flashes of gamma radiation. They come from all different directions of the sky and last from a few milliseconds to a few hundred seconds. So far scientists do not know what causes them. Do they signal the birth of a black hole in a massive stellar explosion? Are they the product of the collision of two neutron stars? Or is it some other exotic phenomenon that causes these bursts?
With Swift, a NASA mission with international participation, scientists have a tool dedicated to answering these questions and solving the gamma-ray burst mystery. Its three instruments give scientists the ability to scrutinize gamma-ray bursts like never before. Within seconds of detecting a burst, Swift relays its location to ground stations, allowing both ground-based and space-based telescopes around the world the opportunity to observe the burst's afterglow. Swift is part of NASA's medium explorer (MIDEX) program and was launched into a low-Earth orbit on a Delta 7320 rocket on November 20, 2004. The Principal Investigator is Dr. Neil Gehrels (NASA-GSFC).
All Swift systems are operating normally.
Gamma-ray bursts are among the most energetic and explosive events in the universe. They are also short-lived, lasting from a few milliseconds to about a minute. This has made it tough for astronomers to observe a gamma-ray burst in detail. Using a wide array of ground- and space-based telescopes, including NASA's Swift and Fermi satellites, an international team led by Eleonora Troja constructed one of the most detailed descriptions of a gamma-ray burst to date. The event, named GRB 160625B, revealed key details about the initial "prompt" phase of gamma-ray bursts and the evolution of the large jets of matter and energy that form as a result of the burst. The group's findings are published in the July 27, 2017 issue of the journal Nature.
In early 2016 NASA's Swift mission started an intensive high-cadence monitoring campaign of NGC 4151, one of the nearest galaxies to contain an actively accreting supermassive black hole at its center. Swift looked at the galaxy's nucleus every 6 hours for 69 consecutive days in order to constrain its temporal variability at X-ray, ultraviolet and optical energies. This technique allows Swift to probe the central regions of AGN in which the bulk of the luminosity is produced and emitted. The results of these observations were published today on the Astrophysical Journal. The study, led by researcher Rick Edelson, found that the Swift data rule out the standard reprocessing model for AGN and instead favor the presence of two separate reprocessings: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component, which illuminates the disk and drives its variability.
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