Swift: Gamma-ray Bursts

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  • NASA Missions Unveil Magnetar Eruptions in Nearby Galaxies
    2021.01.13
    On April 15, 2020, a brief burst of high-energy light swept through the solar system, triggering instruments on many NASA missions. Now, multiple international science teams conclude that the blast came from a supermagnetized stellar remnant known as a magnetar located in a neighboring galaxy. This finding confirms long-held suspicions that some gamma-ray bursts (GRBs) – cosmic eruptions detected somewhere in the sky almost daily – are in fact powerful flares from magnetars relatively close to home. The April 15 event is a game changer because its estimated location lies entirely within the disk of the galaxy NGC 253, located 11.4 million light-years away GRBs, the most powerful explosions in the cosmos, can be detected across billions of light-years. Those lasting less than about two seconds, called short GRBs, occur when a pair of orbiting neutron stars both the crushed remnants of exploded stars spiral into each other and merge. Magnetars are neutron stars with the strongest-known magnetic fields, with up to a thousand times the intensity of typical neutron stars and up to 10 trillion times the strength of a refrigerator magnet. Rarely, magnetars produce enormous eruptions called giant flares that produce gamma rays, the highest-energy form of light. Shortly before 4:42 a.m. EDT on April 15, a powerful burst of X-rays and gamma rays triggered, in turn, instruments on NASA's Mars Odyssey mission, Wind satellite, and Fermi Gamma-ray Space Telescope. A ground-based analysis of data from NASA's Neil Gehrels Swift Observatory show that it also detected the event. The pulse of radiation lasted just 140 milliseconds, as fast as a blink of the eye or a finger snap. Fermi's Large Area Telescope (LAT) also detected high-energy gamma rays up to several minutes after this pulse, a surprising finding. Analysis of Fermi and Swift data indicate that the outburst launched a blob of electrons and positrons moving at about 99% the speed of light. The blob expanded as it traveled, following closely behind the light emitted by the giant flare. After a few days, scientists say, they reached the boundary separating the magnetar's region of influence from interstellar space. The light passed through, followed many seconds later by the greatly expanded cloud. This material induced shock waves in gas piled up at the boundary, and the interaction produced the highest-energy emission detected by the LAT.
  • A New Era in Gamma-ray Science
    2019.11.20
    A pair of distant explosions discovered by NASA’s Fermi Gamma-ray Space Telescope and Neil Gehrels Swift Observatory have produced the highest-energy light yet seen from these events, called gamma-ray bursts (GRBs). The detections, made by two different ground-based observatories, provide new insights into the mechanisms driving gamma-ray bursts. Astronomers first recognized the GRB phenomenon 46 years ago. The blasts appear at random locations in the sky about once a day, on average. The most common type of GRB occurs when a star much more massive than the Sun runs out of fuel. Its core collapses and forms a black hole, which then blasts jets of particles outward at nearly the speed of light. These jets pierce the star and continue into space. They produce an initial pulse of gamma rays — the most energetic form of light — that typically lasts about a minute. As the jets race outward, they interact with surrounding gas and emit light across the spectrum, from radio to gamma rays. These so-called afterglows can be detected up to months — and rarely, even years — after the burst at longer wavelengths. Much of what astronomers have learned about GRBs over the past couple of decades has come from observing their afterglows at lower energies. Now, thanks to these new ground-based detections, they're seeing the gamma rays from GRBs in a whole new way. On Jan. 14, 2019, just before 4 p.m. EST, both the Fermi and Swift satellites detected a spike of gamma rays from the constellation Fornax. The missions alerted the astronomical community to the location of the burst, dubbed GRB 190114C. One facility receiving the alerts was the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observatory, located on La Palma in the Canary Islands, Spain. Both of its 17-meter telescopes automatically turned to the site of the fading burst. They began observing the GRB just 50 seconds after it was detected and captured the most energetic gamma rays yet seen from these events. The energy of visible light ranges from about 2 to 3 electron volts. In 2013, Fermi’s Large Area Telescope detected light reaching an energy of 95 billion electron volts (GeV), then the highest seen from a burst. This falls just shy of 100 GeV, the threshold for so-called very high-energy (VHE) gamma rays. With GRB 190114C, MAGIC became the first facility to report unambiguous VHE emission, with energies up to a trillion electron volts. That’s 10 times the peak energy Fermi has seen to date. Data from a different burst, which Fermi and Swift both discovered, confirm afterglows reach these energies. Ten hours after the alerts, the High Energy Stereoscopic System (H.E.S.S.) pointed its large, 28-meter gamma-ray telescope to the location of the burst, called GRB 180720B. A careful analysis carried out during the weeks following the event revealed that H.E.S.S. clearly detected VHE gamma rays with energies up to 440 GeV. Even more remarkable, the glow continued for two hours following the start of the observation. Catching this emission so long after the GRB’s detection is both a surprise and an important new discovery.
  • Swift: A Decade of Game-Changing Astrophysics
    2014.11.20
    Over the past decade, NASA's Swift Gamma-ray Burst Explorer has proven itself to be one of the most versatile astrophysics missions ever flown. It remains the only satellite capable of precisely locating gamma-ray bursts -- the universe's most powerful explosions -- and monitoring them across a broad range of wavelengths using multiple instruments before they fade from view. "Swift" isn't just a name -- it's a core capability, a part of the spacecraft's DNA. Gamma-ray bursts (GRBs) typically last less than a minute and Swift detects one event about twice a week. Once Swift observes a GRB, it automatically determines the blast's location, broadcasts the position to the astronomical community, and then turns toward the site to investigate with its own sensitive telescopes. In addition to its studies of GRBs, Swift conducts a wide array of observations of other astrophysical phenomena. A flexible planning system enables astronomers to request Swift "target-of-opportunity" (TOO) observations, which can be commanded from the ground in as little as 10 minutes, or set up monitoring programs to observe specific sources at time intervals ranging from minutes to months. The system can schedule up to 75 independent targets a day. Earlier this year, Swift ranked highly in NASA's 2014 Senior Review of Operating Missions and will continue its enormously productive scientific work through at least 2016.
  • Doomed Neutron Stars Create Blast of Light and Gravitational Waves
    2017.10.16
    For the first time, NASA scientists have detected light tied to a gravitational-wave event, thanks to two merging neutron stars in the galaxy NGC 4993, located about 130 million light-years from Earth in the constellation Hydra. Shortly after 8:41 a.m. EDT on Aug. 17, NASA's Fermi Gamma-ray Space Telescope picked up a pulse of high-energy light from a powerful explosion, which was immediately reported to astronomers around the globe as a short gamma-ray burst. The scientists at the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves dubbed GW170817 from a pair of smashing stars tied to the gamma-ray burst, encouraging astronomers to look for the aftermath of the explosion. Shortly thereafter, the burst was detected as part of a follow-up analysis by ESA’s (European Space Agency’s) INTEGRAL satellite. NASA's Swift, Hubble, Chandra and Spitzer missions, along with dozens of ground-based observatories, including the NASA-funded Pan-STARRS survey, later captured the fading glow of the blast's expanding debris. Neutron stars are the crushed, leftover cores of massive stars that previously exploded as supernovas long ago. The merging stars likely had masses between 10 and 60 percent greater than that of our Sun, but they were no wider than Washington, D.C. The pair whirled around each other hundreds of times a second, producing gravitational waves at the same frequency. As they drew closer and orbited faster, the stars eventually broke apart and merged, producing both a gamma-ray burst and a rarely seen flare-up called a "kilonova." Neutron star mergers produce a wide variety of light because the objects form a maelstrom of hot debris when they collide. Merging black holes -- the types of events LIGO and its European counterpart, Virgo, have previously seen -- very likely consume any matter around them long before they crash, so we don't expect the same kind of light show. Within hours of the initial Fermi detection, LIGO and the Virgo detector at the European Gravitational Observatory near Pisa, Italy, greatly refined the event's position in the sky with additional analysis of gravitational wave data. Ground-based observatories then quickly located a new optical and infrared source -- the kilonova -- in NGC 4993. To Fermi, this appeared to be a typical short gamma-ray burst, but it occurred less than one-tenth as far away as any other short burst with a known distance, making it among the faintest known. Astronomers are still trying to figure out why this burst is so odd, and how this event relates to the more luminous gamma-ray bursts seen at much greater distances. NASA’s Swift, Hubble and Spitzer missions followed the evolution of the kilonova to better understand the composition of this slower-moving material, while Chandra searched for X-rays associated with the remains of the ultra-fast jet.
  • Briefing Materials: NASA Missions Explore Record-Setting Cosmic Blast
    2013.11.21
    On Thursday, Nov. 21, 2013, NASA held a media teleconference to discuss new findings related to a brilliant gamma-ray burst detected on April 27. Audio of the teleconference is available for download. Related feature story: www.nasa.gov/content/goddard/nasa-sees-watershed-cosmic-blast-in-unique-detail/. Audio of Sylvia Zhu interview for a Science Podcast.
    Briefing Speakers
    Introduction: Paul Hertz, NASA Astrophysics Division Director, NASA Headquarters, Washington, D.C. Charles Dermer, astrophysicist, Naval Research Laboratory, Washington, D.C. Thomas Vestrand, astrophysicist, Los Alamos National Laboratory, Los Alamos, N.M. Chryssa Kouveliotou, astrophysicist, NASA’s Marshall Space Flight Center, Huntsville, Ala.
    Presenter 1: Charles Dermer

    Presenter 2: Thomas Vestrand

    Presenter 3: Chryssa Kouveliotou

    Additional Media
  • Swift's 500 Gamma-ray Bursts
    2010.04.19
    On April 13, 2010, NASA's Swift Gamma-ray Burst Explorer satellite discovered its 500th burst. Swift's main job is to quickly localize each gamma-ray burst (GRB), report its position so that others can immediately conduct follow-up observations, and then study the burst using its X-ray and Ultraviolet/Optical telescopes. The plots and videos below illustrate Swift's first 500 GRBs.

    For more on the story, see the feature "NASA's Swift Catches 500th Gamma-ray Burst"

    http://www.nasa.gov/mission_pages/swift/bursts/500th.html.

    This page has been updated with a new version of this animation highlighting Swift's detection of the most distant gamma-ray burst ever seen—13.14 billion light years.

  • The Dual Personality of the 'Christmas Burst'
    2011.11.30
    The Christmas burst, also known as GRB 101225A, was discovered in the constellation Andromeda by Swift's Burst Alert Telescope at 1:38 p.m. EST on Dec. 25, 2010. Two very different scenarios successfully reproduce features of this peculiar cosmic explosion. It was either caused by novel type of supernova located billions of light-years away or an unusual collision much closer to home, within our own galaxy.

    Common to both scenarios is the presence of a neutron star, the crushed core that forms when a star many times the sun's mass explodes.

    According to one science team, the burst occurred in an exotic binary system where a neutron star orbited a normal star that had just entered its red giant phase. The outer atmosphere of the giant expanded so much that it engulfed the neutron star, which resulted in both the ejection of the giant's atmosphere and rapid tightening of the neutron star's orbit.

    Once the two stars became wrapped in a common envelope of gas, the neutron star may have merged with the giant's core after just five orbits, or about 18 months. The end result of the merger was the birth of a black hole and the production of oppositely directed jets of particles moving at nearly the speed of light, which made the gamma rays, followed by a weak supernova. Based on this interpretation, the event took place about 5.5 billion light-years away, and the team has detected what may be a faint galaxy at the right location.

    Another team supports an alternative model that involves the tidal disruption of a large comet-like object and the ensuing crash of debris onto a neutron star located only about 10,000 light-years away.

    Gamma-ray emission occurred when debris fell onto the neutron star. Clumps of cometary material likely made a few orbits, with different clumps following different paths before settling into a disk around the neutron star. X-ray variations detected by Swift's X-Ray Telescope that lasted several hours may have resulted from late-arriving clumps that struck the neutron star as the disk formed.

    The NASA release is here.

  • Swift Detects its 500th Gamma Ray Burst
    2010.04.19
    The NASA Swift mission has detected 500 gamma-ray bursts (GRBs) to-date.

    This movie is presented as an all-sky map in a Hammer projection (Wikipedia). Each burst lights on the appropriate date and then fades to a green dot to emphasize the random distribution of GRBs on the sky.

    Another version of this visualization is available at Swift's 500 Gamma-ray Bursts.

  • A Trio of Swift Bursts Form A New Class of GRBs
    2013.04.16
    Three unusually long-lasting stellar explosions discovered by NASA's Swift satellite represent a previously unrecognized class of gamma-ray bursts (GRBs). Two international teams of astronomers studying these events conclude that they likely arose from the catastrophic death of supergiant stars hundreds of times larger than the sun.

    GRBs are the most luminous and mysterious explosions in the universe. The blasts emit surges of gamma rays — the most powerful form of light — as well as X-rays, and they produce afterglows that can be observed at optical and radio energies. Swift, Fermi and other spacecraft detect an average of about one GRB each day.

    Traditionally, astronomers have recognized two GRB types, short and long, based on the duration of the gamma-ray signal. Short bursts last two seconds or less and are thought to represent a merger of compact objects in a binary system, with the most likely suspects being neutron stars and black holes. Long GRBs may last anywhere from several seconds to several minutes, with typical durations falling between 20 and 50 seconds. These events are thought to be associated with the collapse of a star several times the sun's mass and the resulting birth of a new black hole.

    Both scenarios give rise to powerful jets that propel matter at nearly the speed of light in opposite directions. As they interact with matter in and around the star, the jets produce a spike of high-energy light.

    A detailed study of GRB 111209A, which erupted on Dec. 9, 2011, and continued to produce high-energy emission for an astonishing seven hours, making it by far the longest-duration GRB ever recorded.

    Another event, GRB 101225A, exploded on Christmas Day in 2010 and produced high-energy emission for at least two hours. Subsequently nicknamed the "Christmas burst," the event's distance was unknown, which led two teams to arrive at radically different physical interpretations. One group concluded the blast was caused by an asteroid or comet falling onto a neutron star within our own galaxy. Another team determined that the burst was the outcome of a merger event in an exotic binary system located some 3.5 billion light-years away.

    Using the Gemini North Telescope in Hawaii, a team led by Andrew Levan at the University of Warwick in Coventry, England, obtained a spectrum of the faint galaxy that hosted the Christmas burst. This enabled the scientists to identify emission lines of oxygen and hydrogen and determine how much these lines were displaced to lower energies compared to their appearance in a laboratory. This difference, known to astronomers as a redshift, places the burst some 7 billion light-years away.

    Levan and his colleagues also examined 111209A and the more recent burst 121027A, which exploded on Oct. 27, 2012. All show similar X-ray, ultraviolet and optical emission and all arose from the central regions of compact galaxies that were actively forming stars. The astronomers conclude that all three GRBs constitute a hitherto unrecognized group of "ultra-long" bursts.

    To account for the normal class of long GRBs, astronomers envision a star similar to the size sun's size but with many times its mass. The mass must be high enough for the star to undergo an energy crisis, with its core ultimately running out of fuel and collapsing under its own weight to form a black hole. Some of the matter falling onto the nascent black hole becomes redirected into powerful jets that drill through the star, creating the gamma-ray spike, but because this burst is short-lived, the star must be comparatively small.

    Because ultra-long GRBs persist for periods up to 100 times greater than long GRBs, they require a stellar source of correspondingly greater physical size. Both groups suggest that the likely candidate is a supergiant, a star with about 20 times the sun's mass that still retains its deep hydrogen atmosphere, making it hundreds of times the sun's diameter.

    Watch this video on YouTube.

  • NASA's Fermi, Swift See 'Shockingly Bright' Gamma-ray Burst
    2013.05.03
    A record-setting blast of gamma rays from a dying star in a distant galaxy has wowed astronomers around the world. The eruption, which is classified as a gamma-ray burst, or GRB, and designated GRB 130427A, produced the highest-energy light ever detected from such an event.

    The GRB lasted so long that a record number of telescopes on the ground were able to catch it while space-based observations were still ongoing.

    Just after 3:47 a.m. EDT on Saturday, April 27, Fermi's Gamma-ray Burst Monitor (GBM) triggered on an eruption of high-energy light in the constellation Leo. The burst occurred as NASA's Swift satellite was slewing between targets, which delayed its Burst Alert Telescope's detection by less than a minute.

    Fermi's Large Area Telescope (LAT) recorded one gamma ray with an energy of at least 94 billion electron volts (GeV), or some 35 billion times the energy of visible light, and about three times greater than the LAT's previous record. The GeV emission from the burst lasted for hours, and it remained detectable by the LAT for the better part of a day, setting a new record for the longest gamma-ray emission from a GRB.

    The burst subsequently was detected in optical, infrared and radio wavelengths by ground-based observatories, based on the rapid accurate position from Swift. Astronomers quickly learned that the GRB was located about 3.6 billion light-years away, which for these events is relatively close.

    Gamma-ray bursts are the universe's most luminous explosions. Astronomers think most occur when massive stars run out of nuclear fuel and collapse under their own weight. As the core collapses into a black hole, jets of material shoot outward at nearly the speed of light.

    The jets bore all the way through the collapsing star and continue into space, where they interact with gas previously shed by the star and generate bright afterglows that fade with time.

    If the GRB is near enough, astronomers usually discover a supernova at the site a week or so after the outburst.

    This GRB is in the closest 5 percent of bursts, so ground-based observatories are monitoring its location in hopes of finding an underlying supernova.

  • Naked-Eye Gamma-ray Burst Model for GRB 080319B
    2009.01.15
    Gamma-ray bursts that are longer than two seconds are caused by the detonation of a rapidly rotating massive star at the end of its life on the main sequence. Jets of particles and gamma radiation are emitted in opposite directions from the stellar core as the star collapses. In this model, a narrow beam of gamma rays is emitted, followed by a wider beam of gamma rays. The narrow beam for GRB 080319B was aimed almost precisely at the Earth, which made it the brightest gamma-ray burst observed to date by NASA's Swift satellite.
  • Gamma Ray Burst
    2008.05.22
    This animation was used to illustrate a gamma ray burst that NASA's SWIFT might see.
  • NASA's Swift Catches its 1,000th Gamma-ray Burst
    2015.11.06
    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. A GRB is a fleeting blast of high-energy light, often lasting a minute or less, occurring somewhere in the sky every couple of days. Scientists are looking for exceptional bursts that offer the deepest insights into the extreme physical processes at work. Shortly before 6:41 p.m. EDT on Oct. 27, Swift's Burst Alert Telescope detected GRB 1,000 as a sudden pulse of gamma rays arising from a location toward the constellation Eridanus. Astronomers dubbed the event GRB 151027B, after the detection date and the fact that it was the second burst of the day. Swift automatically determined its location, broadcast the position to astronomers around the world, and turned to investigate the source with its own sensitive X-ray, ultraviolet and optical telescopes. Astronomers classify GRBs by their duration. Like GRB 151027B, roughly 90 percent of bursts are of the "long" variety, where the gamma-ray pulse lasts more than two seconds. They are believed to occur in a massive star whose core has run out of fuel and collapsed into a black hole. As matter falls toward the newly formed black hole, it launches jets of subatomic particles that move out through the star's outer layers at nearly the speed of light. When the particle jets reach the stellar surface, they emit gamma rays, the most energetic form of light. In many cases, the star is later seen to explode as a supernova.
  • When Neutron Stars Collide
    2011.04.07
    Armed with state-of-the-art supercomputer models, scientists have shown that colliding neutron stars can produce the energetic jet required for a gamma-ray burst. Earlier simulations demonstrated that mergers could make black holes. Others had shown that the high-speed particle jets needed to make a gamma-ray burst would continue if placed in the swirling wreckage of a recent merger.

    Now, the simulations reveal the middle step of the process—how the merging stars' magnetic field organizes itself into outwardly directed components capable of forming a jet. The Damiana supercomputer at Germany's Max Planck Institute for Gravitational Physics needed six weeks to reveal the details of a process that unfolds in just 35 thousandths of a second—less than the blink of an eye.

    For the researchers' website, with more video and stills of their simulations, go here.

  • Scientists Watch Baby Black Hole Get to Work Fast
    2008.09.26
    Scientists using NASA's Swift satellite say they have found newborn black holes, just seconds old, in a confused state of existence, sloppily gorging on material falling into them while somehow propelling other material away at great speeds. These black holes are born in massive star explosions. An initial blast obliterates the star. Yet the chaotic black hole activity appears to re-energize the explosion again and again over the course of several minutes. This is a dramatically different view of star death, one that entails multiple explosive outbursts and not just a single bang, as previously thought.

    When a massive star runs out of fuel, it no longer has the energy to support its mass. The core collapses and forms a black hole. Shockwaves bounce out and obliterate the outer shells of the star. Previously scientists thought that a single explosion is followed by a graceful afterglow of the dying embers. Now, according to Swift observations, it appears that a newborn black hole in the core somehow re-energizes the explosion again and again, creating multiple bursts all within a few minutes.

  • Cosmic Explosion Second Only to the Sun in Brightness
    2006.08.18
    The gamma ray flare produced by neutron star SGR 1806-20, traveled 50,000 light years before impacting Earth. The burst was so powerful, that it disrupted Earth's ionosphere. Scientists know of only two other giant flares in the past 35 years, and this December 27, 2005 event was one hundred times more powerful than either of those