Author Topic: NASA - Fermi Gamma-ray Space Telescope updates  (Read 83792 times)

Online jacqmans

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Re: NASA - NASA's Fermi Gamma-ray Space Telescope updates
« Reply #380 on: 08/01/2014 08:52 AM »

July 31, 2014

NASA's Fermi Space Telescope Reveals New Source of Gamma Rays

Observations by NASA's Fermi Gamma-ray Space Telescope of several stellar eruptions, called novae, firmly establish these relatively common outbursts almost always produce gamma rays, the most energetic form of light.

"There's a saying that one is a fluke, two is a coincidence, and three is a class, and we're now at four novae and counting with Fermi," said Teddy Cheung, an astrophysicist at the Naval Research Laboratory in Washington, and the lead author of a paper reporting the findings in the Aug. 1 edition of the journal Science.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

Fermi's Large Area Telescope (LAT) scored its first nova detection, dubbed V407 Cygni, in March 2010. The outburst came from a rare type of star system in which a white dwarf interacts with a red giant, a star more than a hundred times the size of our sun. Other members of the same unusual class of stellar system have been observed "going nova" every few decades.

In 2012 and 2013, the LAT detected three so-called classical novae which occur in more common binaries where a white dwarf and a sun-like star orbit each other every few hours.

"We initially thought of V407 Cygni as a special case because the red giant's atmosphere is essentially leaking into space, producing a gaseous environment that interacts with the explosion's blast wave," said co-author Steven Shore, a professor of astrophysics at the University of Pisa in Italy. "But this can't explain more recent Fermi detections because none of those systems possess red giants."

Fermi detected the classical novae V339 Delphini in August 2013 and V1324 Scorpii in June 2012, following their discovery in visible light. In addition, on June 22, 2012, the LAT discovered a transient gamma-ray source about 20 degrees from the sun. More than a month later, when the sun had moved farther away, astronomers looking in visible light discovered a fading nova from V959 Monocerotis at the same position.

Astronomers estimate that between 20 and 50 novae occur each year in our galaxy. Most go undetected, their visible light obscured by intervening dust and their gamma rays dimmed by distance. All of the gamma-ray novae found so far lie between 9,000 and 15,000 light-years away, relatively nearby given the size of our galaxy.

Novae occur because a stream of gas flowing from the companion star piles up into a layer on the white dwarf's surface. Over time -- tens of thousands of years, in the case of classical novae, and several decades for a system like V407 Cygni -- this deepening layer reaches a flash point. Its hydrogen begins to undergo nuclear fusion, triggering a runaway reaction that detonates the accumulated gas. The white dwarf itself remains intact.

One explanation for the gamma-ray emission is that the blast creates multiple shock waves that expand into space at slightly different speeds. Faster shocks could interact with slower ones, accelerating particles to near the speed of light. These particles ultimately could produce gamma rays.

"This colliding-shock process must also have been at work in V407 Cygni, but there is no clear evidence for it," said co-author Pierre Jean, a professor of astrophysics at the University of Toulouse in France. This is likely because gamma rays emitted through this process were overwhelmed by those produced as the shock wave interacted with the red giant and its surroundings, the scientists conclude.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership managed by the agency's Goddard Space Flight Center in Greenbelt, Maryland. It was developed in collaboration with the U.S. Department of Energy, with contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

For more information about Fermi, visit:

http://www.nasa.gov/fermi

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Re: NASA - NASA's Fermi Gamma-ray Space Telescope updates
« Reply #381 on: 02/12/2016 09:37 AM »
Cross-referencing here from the gravitational wave thread, as this possible GRB coincidence was seen by Fermi.

http://gammaray.nsstc.nasa.gov/gbm/publications/preprints/gbm_ligo_preprint.pdf
-DaviD-

Offline Star One

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NASA - Fermi Gamma-ray Space Telescope updates
« Reply #382 on: 04/18/2016 08:36 PM »
NASA's Fermi Telescope Poised to Pin Down Gravitational Wave Sources

On Sept. 14, waves of energy traveling for more than a billion years gently rattled space-time in the vicinity of Earth. The disturbance, produced by a pair of merging black holes, was captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana. This event marked the first-ever detection of gravitational waves and opens a new scientific window on how the universe works.

Less than half a second later, the Gamma-ray Burst Monitor (GBM) on NASA's Fermi Gamma-ray Space Telescope picked up a brief, weak burst of high-energy light consistent with the same part of the sky. Analysis of this burst suggests just a 0.2-percent chance of simply being random coincidence. Gamma-rays arising from a black hole merger would be a landmark finding because black holes are expected to merge “cleanly,” without producing any sort of light.

“This is a tantalizing discovery with a low chance of being a false alarm, but before we can start rewriting the textbooks we’ll need to see more bursts associated with gravitational waves from black hole mergers,” said Valerie Connaughton, a GBM team member at the National Space, Science and Technology Center in Huntsville, Alabama, and lead author of a paper on the burst now under review by The Astrophysical Journal.

Detecting light from a gravitational wave source will enable a much deeper understanding of the event. Fermi's GBM sees the entire sky not blocked by Earth and is sensitive to X-rays and gamma rays with energies between 8,000 and 40 million electron volts (eV). For comparison, the energy of visible light ranges between about 2 and 3 eV.

With its wide energy range and large field of view, the GBM is the premier instrument for detecting light from short gamma-ray bursts (GRBs), which last less than two seconds. They are widely thought to occur when orbiting compact objects, like neutron stars and black holes, spiral inward and crash together. These same systems also are suspected to be prime producers of gravitational waves.

"With just one joint event, gamma rays and gravitational waves together will tell us exactly what causes a short GRB," said Lindy Blackburn, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and a member of the LIGO Scientific Collaboration. "There is an incredible synergy between the two observations, with gamma rays revealing details about the source's energetics and local environment and gravitational waves providing a unique probe of the dynamics leading up to the event." He will be discussing the burst and how Fermi and LIGO are working together in an invited talk at the American Physical Society meeting in Salt Lake City on Tuesday.

Currently, gravitational wave observatories possess relatively blurry vision. This will improve in time as more facilities begin operation, but for the September event, dubbed GW150914 after the date, LIGO scientists could only trace the source to an arc of sky spanning an area of about 600 square degrees, comparable to the angular area on Earth occupied by the United States.   

“That's a pretty big haystack to search when your needle is a short GRB, which can be fast and faint, but that’s what our instrument is designed to do," said Eric Burns, a GBM team member at the University of Alabama in Huntsville. "A GBM detection allows us to whittle down the LIGO area and substantially shrinks the haystack."

Less than half a second after LIGO detected gravitational waves, the GBM picked up a faint pulse of high-energy X-rays lasting only about a second. The burst effectively occurred beneath Fermi and at a high angle to the GBM detectors, a situation that limited their ability to establish a precise position. Fortunately, Earth blocked a large swath of the burst’s likely location as seen by Fermi at the time, allowing scientists to further narrow down the burst’s position.       

The GBM team calculates less than a 0.2-percent chance random fluctuations would have occurred in such close proximity to the merger. Assuming the events are connected, the GBM localization and Fermi's view of Earth combine to reduce the LIGO search area by about two-thirds, to 200 square degrees. With a burst better placed for the GBM’s detectors, or one bright enough to be seen by Fermi’s Large Area Telescope, even greater improvements are possible.

The LIGO event was produced by the merger of two relatively large black holes, each about 30 times the mass of the sun. Binary systems with black holes this big were not expected to be common, and many questions remain about the nature and origin of the system.

Black hole mergers were not expected to emit significant X-ray or gamma-ray signals because orbiting gas is needed to generate light. Theorists expected any gas around binary black holes would have been swept up long before their final plunge. For this reason, some astronomers view the GBM burst as most likely a coincidence and unrelated to GW150914. Others have developed alternative scenarios where merging black holes could create observable gamma-ray emission. It will take further detections to clarify what really happens when black holes collide.

Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago, and scientists have been attempting to detect them for 50 years. Einstein pictured these waves as ripples in the fabric of space-time produced by massive, accelerating bodies, such as black holes orbiting each other. Scientists are interested in observing and characterizing these waves to learn more about the sources producing them and about gravity itself.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

For more information about NASA's Fermi Gamma-ray Space Telescope, please visit:

www.nasa.gov/fermi

Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Maryland

Last Updated: April 18, 2016
Editor: Ashley Morrow



http://www.nasa.gov/feature/goddard/2016/nasas-fermi-telescope-poised-to-pin-down-gravitational-wave-sources
« Last Edit: 04/18/2016 08:47 PM by Star One »

Offline catdlr

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #383 on: 02/09/2017 08:18 PM »
NASA's Fermi space telescope detected new solar flares

Published on Feb 9, 2017
NASA's Fermi Gamma-ray Space Telescope can now detect solar flares occurring on the side of the sun it cannot see. This could help scientists better understand solar storms and improve forecasts for future outbursts.

Video courtesy of NASA

https://www.youtube.com/watch?v=fL7e2e7IDec?t=001

Tony De La Rosa

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #384 on: 05/16/2017 07:19 PM »

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #385 on: 02/22/2018 08:27 PM »
Novel search strategy advances the hunt for primordial black holes

Quote
Some theories of the early universe predict density fluctuations that would have created small "primordial black holes," some of which could be drifting through our galactic neighborhood today and might even be bright sources of gamma rays.

Researchers analyzing data from the Fermi Gamma-ray Space Telescope for evidence of nearby primordial black holes have come up empty, but their negative findings still allow them to put an upper limit on the number of these tiny black holes that might be lurking in the vicinity of Earth.

https://news.ucsc.edu/2018/02/primordial-black-holes.html

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #386 on: 07/10/2018 03:25 PM »
Word is coming out that the IceCube neutrino detector in Antarctica has detected high-energy neutrinos correlated with a GRB, adding a new critical piece to multi-messenger astronomy.

GRB was detected by FERMI and AGILE in the TXS 0506+056 blazar region, as well as by MAGIC on the ground.

NSF press conference on Thursday (11 am EDT): https://twitter.com/NSF/status/1016413039086784512
-DaviD-

Offline jgoldader

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #387 on: 07/10/2018 06:23 PM »
Might be related to this; if it is, the neutrino is from a gamma ray *source*, a BL Lac (a type of active galaxy), not necessarily a GRB.

https://sciencesprings.wordpress.com/tag/active-galaxy-txs-0506-056/

Still, it's interesting.  Wouldn't this be just the second extragalactic object, after SN 1987A, identified as a neutrino source?  And the third astrophysical source overall, including the Sun?
Recovering astronomer

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #388 on: 07/12/2018 04:22 PM »
Confirmation of the first multi-messenger observation of a high-energy neutrino (IC-170922A of 0.29 PeV at 90% c.l., by IceCube) and EM waves source (by Fermi, MAGIC and a (negative) follow-up by INTEGRAL): blazar TXS 0506+056.

Quote
Fermi was the first telescope to identify enhanced gamma-ray activity from TXS 0506+056 within 0.06 degrees of the IceCube neutrino direction. Over a decade of Fermi observations of this source, this was the strongest flare in gamma rays, the highest-energy photons. A later follow-up by MAGIC detected gamma rays of even higher energies.

High-energy gamma rays can be produced either by accelerated electrons or protons. The observation of a neutrino, a hallmark of proton interactions, is the first definitive evidence of proton acceleration by black holes.

"Now, we have identified at least one source of cosmic rays because it produces cosmic neutrinos," Halzen said. "Neutrinos are the decay products of pions. In order to produce them, you need a proton accelerator."

This also provides the first detection of an astrophysical neutrino point source, apart from the Sun and the only supernova that went off close enough to Earth while neutrino detectors were in operation (SN1987A).

https://www.sciencenews.org/article/high-energy-neutrinos-blazar-icecube


Paper just out: http://science.sciencemag.org/content/early/2018/07/11/science.aat1378.full
« Last Edit: 07/12/2018 04:24 PM by eeergo »
-DaviD-

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #389 on: 07/13/2018 06:08 AM »
July 12, 2018
RELEASE 18-062

NASA’s Fermi Traces Source of Cosmic Neutrino to Monster Black Hole

For the first time ever, scientists using NASA’s Fermi Gamma-ray Space Telescope have found the source of a high-energy neutrino from outside our galaxy. This neutrino traveled 3.7 billion years at almost the speed of light before being detected on Earth. This is farther than any other neutrino whose origin scientists can identify.

High-energy neutrinos are hard-to-catch particles that scientists think are created by the most powerful events in the cosmos, such as galaxy mergers and material falling onto supermassive black holes. They travel at speeds just shy of the speed of light and rarely interact with other matter, allowing them to travel unimpeded across distances of billions of light-years.

The neutrino was discovered by an international team of scientists using the National Science Foundation’s IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station. Fermi found the source of the neutrino by tracing its path back to a blast of gamma-ray light from a distant supermassive black hole in the constellation Orion.

“Again, Fermi has helped make another giant leap in a growing field we call multimessenger astronomy,” said Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington. “Neutrinos and gravitational waves deliver new kinds of information about the most extreme environments in the universe. But to best understand what they’re telling us, we need to connect them to the ‘messenger’ astronomers know best—light.”

Scientists study neutrinos, as well as cosmic rays and gamma rays, to understand what is going on in turbulent cosmic environments such as supernovas, black holes and stars. Neutrinos show the complex processes that occur inside the environment, and cosmic rays show the force and speed of violent activity. But, scientists rely on gamma rays, the most energetic form of light, to brightly flag what cosmic source is producing these neutrinos and cosmic rays.

“The most extreme cosmic explosions produce gravitational waves, and the most extreme cosmic accelerators produce high-energy neutrinos and cosmic rays,” says Regina Caputo of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the analysis coordinator for the Fermi Large Area Telescope Collaboration. “Through Fermi, gamma rays are providing a bridge to each of these new cosmic signals.”

The discovery is the subject of two papers published Thursday in the journal Science. The source identification paper also includes important follow-up observations by the Major Atmospheric Gamma Imaging Cherenkov Telescopes and additional data from NASA’s Neil Gehrels Swift Observatory and many other facilities.

On Sept. 22, 2017, scientists using IceCube detected signs of a neutrino striking the Antarctic ice with energy of about 300 trillion electron volts—more than 45 times the energy achievable in the most powerful particle accelerator on Earth. This high energy strongly suggested that the neutrino had to be from beyond our solar system. Backtracking the path through IceCube indicated where in the sky the neutrino came from, and automated alerts notified astronomers around the globe to search this region for flares or outbursts that could be associated with the event.

Data from Fermi’s Large Area Telescope revealed enhanced gamma-ray emission from a well-known active galaxy at the time the neutrino arrived. This is a type of active galaxy called a blazar, with a supermassive black hole with millions to billions of times the Sun’s mass that blasts jets of particles outward in opposite directions at nearly the speed of light. Blazars are especially bright and active because one of these jets happens to point almost directly toward Earth.

Fermi scientist Yasuyuki Tanaka at Hiroshima University in Japan was the first to associate the neutrino event with the blazar designated TXS 0506+056 (TXS 0506 for short).

“Fermi’s LAT monitors the entire sky in gamma rays and keeps tabs on the activity of some 2,000 blazars, yet TXS 0506 really stood out,” said Sara Buson, a NASA Postdoctoral Fellow at Goddard who performed the data analysis with Anna Franckowiak, a scientist at the Deutsches Elektronen-Synchrotron research center in Zeuthen, Germany. “This blazar is located near the center of the sky position determined by IceCube and, at the time of the neutrino detection, was the most active Fermi had seen it in a decade.”

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States. The NASA Postdoctoral Fellow program is administered by Universities Space Research Association under contract with NASA.

For more about NASA’s Fermi mission, visit:

https://www.nasa.gov/fermi

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #390 on: 07/13/2018 06:08 AM »

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Re: NASA - Fermi Gamma-ray Space Telescope updates
« Reply #391 on: 07/13/2018 06:08 AM »

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