Today the advanced LIGO and Virgo gravitational wave observatories announced the discovery of a new type of gravitational wave signal, likely caused by the collision of two neutron stars. The gravitational wave event occurred on 2017 August 17th, and was accompanied by a gamma-ray burst of short duration. Astronomers across the world began searching for the precise location of this event, quickly tracking it down to the nearby galaxy NGC 4993. Once pin-pointed, the Swift satellite quickly maneuvered to look at the object with its X-ray and UV/optical telescopes. The spacecraft saw no X-rays - a surprise for an event that produced higher-energy gamma rays. Instead, it found a bright and quickly fading flash of ultraviolet (UV) light. This bright UV signal was unexpected and revealed unprecedented details about the aftermath of the collision. The short-lived UV pulse likely came from material blown away by the short-lived disk of debris that powered the gamma-ray burst. The rapid fading of the UV signal suggests that this outflow was expanding with a velocity close to a tenth of the speed of light. The results of the Swift observations were published today on the journal Science. The discovery of this powerful wind was only possible using light, which is why combining gravitational waves and light in what we call 'multi-messenger astronomy' is so important.
KIC 8462852, also known as Boyajian's Star, or Tabby's Star, is one of the most mysterious stellar objects. The star has experienced unusual dips in brightness, up to 20 percent over a matter of days, and undergoes much subtler but longer-term enigmatic dimming trends. None of this behavior is expected for a normal star slightly more massive than the Sun. Speculations have included the idea that the star swallowed a planet and that it is unstable. A more imaginative theory involves an advanced civilization, which could be harvesting energy from the star and causing its brightness to decrease. A new study by Huan Meng and collaborators using NASA's Swift and Spitzer missions reveals less dimming in the infrared light from the star than in its ultraviolet light, suggesting that the cause of the dimming over long periods is likely an uneven dust cloud moving around the star.
For decades, astronomers have tried to pin down why two of the most common types of active galaxies,
known as Type I and Type II galaxies, appear different when observed from Earth. The leading theory, known
as the unified model, explains that the central black holes of Type I and Type II galaxies have the same
fundamental structure, but appear different solely because the galaxies point toward Earth at different angles.
An international team of astronomers tested this model by studying over 800 active galaxies detected by the
Burst Alert Telescope on-board Swift. Their results, published in the journal Nature, suggest that Type I
and Type II galaxies do not just appear different--they are, in fact, very different from each other.
Black holes in Type I galaxies consumes matter at a much higher rate and are therefore more efficient at emitting energy.
To give more time to proposers who are without power because of Hurricane Irma, the due date of the Swift GI Cycle 14 proposals is delayed by 1 week. The new Phase-1 proposals are due by September 28, 2017, 4:30 PM Eastern time via the Swift ARK/RPS web page.
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.
Thanks to its unique capabilities, NASA's Swift mission is uniquely poised to characterize the activity and evolution of comets, and active asteroids. Swift's sensitivity at ultraviolet wavelenghts allows scientists to detect hydroxyl, an important tracer of cometary activity formed when water molecules are destroyed by solar UV light. Astronomer Dennis Bodewits, a research scientist at the University of Maryland, uses Swift to follow several Oort Cloud comets and over 15 different asteroids as they cruise through our Solar System. Thanks to extensive Swift observing campaigns, Bodewits obtained spectacular images of the comet Siding Spring during its Mars flyby and spotted a rare and violent collision between two asteroids. These results were honored by the asteroid (10033) Bodewits, named after the lead author of the Swift studies. The announcement was made during the third 'Asteroids, Comets, and Meteroids' meeting, held in Montevideo, Uruguay.
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On September 23, 2012 NASA's Swift satellite discovered a bright flash of gamma-rays produced by the explosion of a star. The event, dubbed GRB120923A, was rapidly localized by the X-ray Telescope on-aboard Swift, and later observed with a wide array of optical and infrared telescopes. An international team of astronomers, led by Nial Tanvir at the University of Leicester, found that the explosion happened when the Universe was only 670 million years old, less than five percent of its present age. Only two of the more than 1,000 gamma-ray bursts seen with Swift have earlier measured ages. Gamma-ray bursts represent a powerful tracer of star-formation in the early Universe, and are the only known signature of primordial stars at such distances.
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Some 290 million years ago, a star much like the sun wandered too close to the central black hole of its galaxy. Intense tides tore the star apart, which produced an eruption of optical, ultraviolet and X-ray light that first reached Earth in 2014. Now, a team of scientists using observations from NASA's Swift satellite have mapped out how and where these different wavelengths were produced in the event, named ASASSN-14li, as the shattered star's debris circled the black hole.
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Dr. Neil Gehrels, Principal Investigator of the Swift Mission, passed away this morning surrounded by his family. Neil had been battling pancreatic cancer and his health declined rapidly over the past several weeks. Neil was the Chief of the Astroparticle Physics Laboratory at NASA's Goddard Space Flight Center, a member of the National Academy of Sciences, of the American Academy of Arts and Sciences, and a honorary fellow of the Royal Astronomical Society. Neil's work primarily focused on time domain astronomy, including gamma-ray bursts, supernovae, tidal disruption events and gravitational waves.
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Swift Cycle 13 Recommended Targets and Proposals have been posted.