NASA's Swift spacecraft has detected its 1,000th gamma-ray burst (GRB). GRBs are the most powerful explosions in the universe, typically associated with the collapse of a massive star and the birth of a black hole.
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The baffling and strange behaviors of black holes have become somewhat less mysterious recently, with new observations from NASA's Explorer missions Swift and the Nuclear Spectroscopic Telescope Array, or NuSTAR.
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New details about what happens when a black hole tears apart a star have been gathered by a multi-national astronomy team using a trio of orbiting of orbiting observatories that includes NASA's Swift Gamma-ray-Burst Explorer.
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NASA received 185 proposals, requesting a total observing time of 15.8 Ms and $6.0M in funds for 1,555 targets. Considering PIs and Co-Is, more than 600 individual scientists responded to the Swift Cycle 12 call. The Swift Cycle 12 Peer Review will be held in December to evaluate the merits of submitted proposals. Results will be posted in late December 2015.
For details on the Swift Cycle 12 program elements and how to submit proposals, see the Swift Cycle 12 information page and the Cycle 12 FAQ.
GRBs usually only last a few seconds, but in very rare cases the gamma rays continue for hours. One such ultra-long duration GRB was picked up by the Swift satellite on 9 December 2011 and named GRB 111209A. It was both one of the longest and brightest GRBs ever observed. In the favoured scenario of a massive star collapse (sometimes known as a collapsar) the decay of radioactive nickel-56 formed in the GRB explosion powers a supernova emission, peaking in the optical several weeks after the GRB. But in the case of GRB 111209A ground-based observations showed that this could not be the case. Follow-up observations from ESO's La Silla and Paranal Observatories in Chile have for the first time demonstrated a link between this very long-lasting burst of gamma rays and an unusually bright supernova explosion. The results show that the supernova was not driven by radioactive decay, as expected, but was instead powered by the decaying super-strong magnetic fields around an exotic object called a magnetar. Magnetars are thought to be the most strongly magnetised objects in the known Universe. This is the first time that such an unambiguous connection between a GRB, a supernova and a magnetar has been possible.
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What looks like a shooting target is actually an image of nested rings of X-ray light centered on an erupting black hole. On June 15, NASA's Swift satellite detected the start of a new outburst from V404 Cygni, where a black hole and a sun-like star orbit each other. Since then, astronomers around the world have been monitoring the ongoing light show.
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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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Not all the universe's clocks tick reliably. After decades of stability, a fast-rotating baby pulsar called B0540-69 recently slammed on its brakes. It's the brightest and youngest one we've ever seen shift its identity this way, and its unpredictable behaviour will help astronomers figure out why pulsars shine in the first place, what makes them stable and what shakes them up.
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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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The Swift Data Center is now reprocessing the Swift data for the entire mission in chronological order using the current version of the SDC pipeline (v. 3.16.08). All the data for 2005 have been reprocessed and delivered to the HEASARC. The archives in Italy and UK are currently populating their archives with the new data. Currently the reprocessing rate is about 3 months per month.
A team of astronomers found that type Ia supernovae commonly used to measure distances in the universe fall into distinct populations not recognized before. The data collected with Swift were crucial because the differences between the populations are subtle in visible light, which had been used to detect type Ia supernovae previously, but became obvious only through Swift's dedicated follow-up observations in the ultraviolet. These findings have important implications for our understanding of how fast the universe has been expanding since the Big Bang: the study concludes that some of the reported acceleration of the universe can be explained by color differences between the two groups of supernovae, leaving less acceleration than initially reported. This would, in turn, require less dark energy than currently assumed.
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On January 15, 2015 the Burst Alert Telescope on-board Swift triggered on a large flare from the RS CVn binary system SZ Psc. Preliminary analysis from the Swift team reports that the observed peak X-ray flux corresponds to an X-ray luminosity of 4.6 x 10^33 erg/s, which is one of the most luminous flares in X-rays ever seen from any active late-type star.
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Swift Cycle 11 Recommended Targets and Proposals have been posted.