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.
NASA's Swift satellite detected a rising tide of high-energy X-rays from the constellation Cygnus on June 15, just before 2:32 p.m. EDT. About 10 minutes later, the Japanese experiment on the International Space Station called the Monitor of All-sky X-ray Image (MAXI) also picked up the flare.
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Gamma-ray bursts are traditionally divided in two classes, "long" and "short", based on whether their duration is more or less than two seconds. Long GRB are originated by the collapse of very massive stars, while short GRBs are produced by the collision or merger of two compact objects. In 2006 Swift discovered a hybrid event , the "long-short" GRB 060614, which displayed properties typical of both classes. Astronomers have been trying to understand the nature of this unusual explosion for years.
In a new study published in Nature Communications researchers at the Purple Mountain Observatory, Hebrew University and INAF/Brera Astronomical Observatory found evidence for a short-lived infrared transient - called macronova or kilonova - in the data of GRB 060614. The discovery of a macronova could solve a long-standing puzzle, as it confirms that the gamma-ray burst GRB 060614 came from the merger of a neutron star and a stellar-mass black hole. It also suggests that mergers of compact objects could be the primary sites of production of the heavy elements, such as gold, uranium, and silver.
Type Ia supernovae are violent stellar explosions used by astronomers to measure the accelerating expansion of the Universe. They are commonly theorized to be the thermonuclear explosions of a white dwarf star that is part of a binary system. How this white dwarf goes from binary star system to Type Ia supernova is a vivid matter of debate. New observations made by the Swift satellite provided an unprecedented clue to the origin of Type Ia explosions. The UVOT telescope aboard Swift started observing the Type Ia supernova iPTF14atg only four days after the explosion, and unveiled a bright pulse of ultraviolet emission. This is consistent with theoretical expectations of collision between material being ejected from a supernova explosion and the companion star from which it has been accreting matter. Alternative models, involving the merger of two white dwarfs, are instead disfavored by the Swift data. These results show that early time ultraviolet observations of young supernovae could hold the key to fully understanding the pre-explosion interaction between a supernova's white dwarf progenitor and its companion.
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