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  • richardmitnick 10:22 am on October 2, 2017 Permalink | Reply
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    From astrobites: “The Science of the Next Generation” 

    Astrobites bloc


    Oct 2, 2017
    Kelly Malone

    Title: Science with the Cherenkov Telescope Array
    Authors: The Cherenkov Telescope Array Consortium
    Status: To be published in the International Journal of Modern Physics D, [open access]

    Today’s document shows the far-reaching goals of the next-generation gamma-ray experiment, the Cherenkov Telescope Array (CTA).

    Cherenkov Telescope Array, http://www.isdc.unige.ch/cta/ at Cerro Paranal, located in the Atacama Desert of northern Chile on Cerro Paranal at 2,635 m (8,645 ft) altitude, 120 km (70 mi) south of Antofagasta; and at at the Instituto de Astrofisica de Canarias (IAC), Roque de los Muchachos Observatory in La Palma, Spain

    MAGIC Cherenkov gamma ray telescope on the Canary island of La Palma, Spain

    HESS Cherenko Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg

    Gamma rays are important probes of cosmic rays, charged particles of which the origins and acceleration mechanisms are still unknown. Over the course of a hefty 211 pages and representing years of work, the authors explain the science goals of this experiment, which will greatly enhance our knowledge of the universe when it comes online in a few years.

    Gamma rays are the radiation at the far end of the electromagnetic spectrum. Gamma rays are created in the same astrophysical processes that create cosmic rays, but since they are electrically neutral, they do not bend in magnetic field lines on their journey to Earth and therefore point back to their sources. Astrophysical TeV gamma rays, which CTA will probe, were first detected in the late 1980s. Many experiments have been built in this energy range since then, but CTA will offer improvements in sensitivity and energy range over all of the current and past experiments.

    CTA will consist of two arrays of differently-sized telescopes (one in the Northern Hemisphere and one in the Southern Hemisphere) that will detect the Cherenkov radiation that is produced when a gamma ray interacts with molecules in our atmosphere. The Southern site, in Chile, will have 99 large, medium, and small-sized telescopes, while the Northern site, in Spain, will only have 19 medium and small ones. (This discrepancy is because the inner regions of our Galaxy, one of the key science targets, is only visible in the Southern hemisphere). These telescopes will look quite different from the conventional optical telescopes you may be used to. Veritas, one of the current generation experiments, has an explanation of their telescope design here.

    Figure 1: The differential sensitivity of CTA, as compared to current gamma-ray experiments. The curves show the particle flux needed for a five sigma detection as a function of energy. A line further down the plot means that the experiment is sensitive to dimmer sources. (Source: Figure 1.1 from the document)

    As CTA will contain more telescopes than current telescope array, it is an immediate improvement. For example, the sensitivity will increase by an order of magnitude at 1 TeV, the angular resolution will improve (leading to the ability to image the tiny sources as well as details in larger ones) and the energy range will be from 20 GeV-300 TeV (HAWC, another gamma-ray experiment, currently has the highest energy range but maxes out around 100 TeV).

    HAWC High Altitude Cherenkov Gamma Ray Collaboration, Sierra Negra volcano near Puebla, Mexico

    Unlike other gamma-ray experiments, CTA will be an open observatory. This means that any scientist will be able to submit Guest Observer proposals to study sources of interest. Additionally, all data will become publicly available one year after it is collected. Approximately 40% of the observing time will be reserved for a Core Program of Key Science Projects, decided of a series of workshops over the years.

    The Key Science projects are far reaching and cover many areas of astrophysics: in-depth observations of the Galactic Centre and a survey of the Galactic Plane, studies of the Large Magellanic Cloud, robust programs for extragalactic sources and transients, searches for cosmic ray PeVatrons, and study galaxy clusters, and star forming systems are just some of the science that will be covered. Additionally, there will be a dark matter program and some opportunity to study other, non-gamma ray science.

    Figure 2: A zoomed in portion a simulated galactic plane, showing what CTA might expect to observe. The plot covers 20 degrees in Galactic longitude (Source: Figure 1.2 from the paper)

    The questions that these science programs will answer will cover three broad themes that probe some of the biggest unknowns in our universe. Theme #1 is “Understanding the Origin and Role of Relativistic Cosmic Particles“. This is where the Collaboration will attempt to answer questions such as the sites and mechanisms of cosmic particle acceleration and the role these particles play in star formation and galaxy evolution. Theme #2, “Probing Extreme Environments“, will deal with the physical processes that occur close to neutron stars and black holes, including their jets, winds, and the explosions that are prone to happening in these environments. Theme #3, “Exploring Frontiers in Physics” deals with fundamental questions about the nature of dark matter, including whether axion-like particles exist and where quantum gravity affects how photons propagate through space.

    CTA will not be online for quite a few years- although the collaboration and idea has existed in some form for the better part of a decade, the sites were only chosen that year and much of the work in the last few years has been related to the telescope design. The project is currently in a “pre-construction” phase, with construction beginning next year, the first observations happening in 2021, and the construction finishing in 2024. When it does come online, though, it will greatly enhance our knowledge of gamma-ray astrophysics.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 11:20 am on December 19, 2016 Permalink | Reply
    Tags: , , Constraints on Dark Matter, , Gamma Ray Detection,   

    From MPIA: “Fluctuations in extragalactic gamma rays reveal two source classes but no dark matter” 


    Max Planck Institute for Astrophysics


    December 19, 2016
    Komatsu, Eiichiro
    Managing director
    Phone: 2208

    Hämmerle, Hannelore
    Press officer
    Phone: 3980gas

    Researchers from the Max Planck Institute for Astrophysics and the University of Amsterdam GRAPPA Center of Excellence just published the most precise analysis so far of the fluctuations in the gamma-ray background. They used more than six years of data gathered by the Fermi Large Area Telescope and found two different source classes contributing to the gamma-ray background. No traces of a contribution of dark matter particles were found in the analysis. The study was performed with an international collaboration of researchers and is published in the journal Physical Review D.

    Gamma rays are particles of light, or photons, with the highest energy in the universe, invisible to the human eye. The most common emitters of gamma rays are blazars: supermassive black holes at the centres of galaxies. In smaller numbers, gammy rays are also produced by a certain kind of stars called pulsars and in huge stellar explosions such as supernovae.

    This view shows the entire sky in gammy ray radiation, at energies greater than 1 GeV, based on five years of data from the Large Area Telescope instrument on NASA’s Fermi Gamma-ray Space Telescope. Brighter colours indicate brighter gamma-ray emission. The large bright band in the middle is the emission from our own Galaxy. [less]
    Credit: NASA/DOE/Fermi LAT Collaboration

    In 2008 NASA launched the Fermi satellite to map the gamma-ray universe with extreme accuracy.

    NASA/Fermi Telescope
    NASA/Fermi Telescope

    The Large Area Telescope, mounted on the Fermi satellite, has been taking data ever since.

    NASA Fermi LAT
    NASA Fermi LAT

    It continuously scans the whole sky every three hours. The majority of the detected gamma rays is produced in our own Galaxy (the Milky Way), but the Fermi telescope also managed to detect more than 3000 extragalactic sources (according to the latest count performed in January 2016). However, these individual sources are not enough to explain the total amount of gamma-ray photons coming from outside our Galaxy. In fact, about 75% of them are unaccounted for.

    Isotropic gamma-ray background

    As far back as the late 1960’s, orbiting observatories have found a diffuse background of gamma rays streaming from all directions in the universe. If you had gamma-ray vision, and looked at the sky, there would be no place that would be dark.

    The source of this so-called isotropic gamma-ray background is hitherto unknown. This radiation could be produced by unresolved blazars, or other astronomical sources too faint to be detected with the Fermi telescope. Parts of the gamma-ray background might also hold the fingerprint of the illustrious dark matter particle, a so-far undetected particle held responsible for the missing 80% of the matter in our universe. If two dark matter particles collide, they can annihilate and produce a signature of gamma-ray photons.


    “The analysis and interpretation of fluctuations of the diffuse gamma-ray background is a new research area in high-energy astrophysics,” explains Eiichiro Komatsu at the Max Planck Institute for Astrophysics, who developed the necessary analysis tools for fluctuations in this radiation. He was also part of the team that for the first time reported fluctuations in the gamma ray background in 2012. For this latest analysis, the researchers used 81 months of data gathered by the Fermi Large Area Telescope – much more data and with a larger energy range than in previous studies.

    The scientists were able to distinguish two different contributions to the gamma-ray background. One class of gamma-ray sources is needed to explain the fluctuations at low energies (below 1 GeV), and another type of sources is needed to generate the fluctuations at higher energy – the signatures of these two contributions is markedly different.

    The gamma rays in the high-energy ranges – from a few GeV up – are likely originating from unresolved blazars, the researchers suggest in their paper. Further investigation of these potential sources is currently under way. However, it seems much harder to pinpoint a source for the fluctuations with energies below 1 GeV. None of the known gamma-ray emitters have a behaviour that is consistent with the new data.

    Constraints on dark matter

    So far, the Fermi telescope has not detected any conclusive indication of gamma-ray emission originating from dark-matter particles. Also this latest study showed no indication of a signal associated with dark matter. “Our measurement complements other search campaigns that used gamma rays to look for dark matter,” says lead author Mattia Fornasa from the University of Amsterdam. “It confirms that there is little room left for dark matter induced gamma-ray emission in the isotropic gamma-ray background.”

    The precision of the fluctuation measurement has improved markedly since the first result in 2012. “I am glad to see that our measurements provide significant new insights into the origin of the gamma-ray background,” says Komatsu.

    “My original motivation to do this analysis in 2006 was to find evidence for gamma-rays from dark matter particles. Well, we have not found gamma-rays from dark matter yet,” Komatsu concedes, “but I am still excited about our measurements leading to a new understanding of populations of astrophysical gamma-ray sources such as blazars. I have not given up hope on finding gamma-rays from dark matter yet though, and we have some new ideas on how to improve our method.”

    See the full article here .

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  • richardmitnick 11:20 am on November 18, 2016 Permalink | Reply
    Tags: , , , Gamma Ray Detection   

    From astrobites: “Plans for a new gamma-ray mission” 

    Astrobites bloc


    Nov 14, 2016
    Kelly Malone

    Title: The e-ASTROGRAM mission: exploring the universe in the MeV-GeV range
    Authors: de Angelis, et. al.
    First Author’s Institution: INFN Padvoa
    Status: To be submitted to Experimental Astronomy

    Today I’m going to take a break from summarizing astronomical results and look to the future instead. Today’s Astrobite concerns the plans for a new gamma-ray observatory: e-ASTROGRAM, which is currently being proposed to the European Space Agency. If selected, it will launch in the 2029.

    Why are gamma-rays important?

    Gamma-ray observatories are designed to study the highest energy radiation in the entire universe (> 100,000 electronvolts). These particles can be generated in a variety of different ways: solar flares, supernova remnants, and gamma-ray bursts are just a few.

    Supernova remnant Crab nebula. NASA/ESA Hubble
    Supernova remnant Crab nebula. NASA/ESA Hubble

    Gamma-ray burst credit NASA SWIFT Cruz Dewilde
    Gamma-ray burst credit NASA SWIFT Cruz Dewilde

    Gamma rays can have energies covering several orders of magnitude (from about the energy involved in the x-ray you would get at a hospital to 10 million times that). It is important to study them in every energy band to get a full picture of how astrophysical phenomena happen. More information about gamma-ray production mechanisms and a brief history of gamma-ray astrophysics and why its important can be found from NASA’s Goddard Space Flight Center.

    e-ASTROGRAM will cover the energy range from 0.3 MeV to 3 GeV. There are a currently a number of both currently-operating and planned gamma-ray experiments, but they cover higher energies than this. The lower energy range is comparatively under-studied compared to higher energies. This mission is meant to be the successor to COMPTEL Telescope, which stopped taking data in 2000. As you can imagine, technology has improved in the last decade and a half and any experiment built today will have much greater sensitivity!

    Current measurements of the extragalactic gamma-ray intensity. The x-axis is the energy, while the y-axis is the energy per second per area (this is a common way to state the intensity of a source at a particular energy). The shaded portion is the parameter space that will be probed by e-ASTROGRAM. Note the current gap in measurements in that energy range (Figure 3 from the paper)

    Science goals of e-ASTROGRAM

    There are many important science goals that can be studied in-depth in the e-ASTROGRAM energy range. The authors run through a few of them, dividing them into broad categories.

    The first is studying jets from objects such as gamma-ray bursts, which are the most energetic explosions known to us. This is important because the MeV energy range, which the instrument will study, is where the transition to an energy spectrum with poorly-understood particle acceleration processes contributing begins. By studying this energy range, one can determine things such as the role of magnetic fields in powering the jets. For more information about magnetic fields and gamma ray, see this link.

    The second science goal is studying how high-energy particles impact galaxy evolution. There is still much to be learned about how cosmic rays (charged particles that interact to create gamma rays) diffuse across interstellar clouds and the effect this has on star formation and galaxy evolution. Our galaxy has an excess of gamma-rays and positrons (antielectrons) toward its center, and it is expected that e-ASTROGRAM will be able to decipher their origins.

    e-ASTROGRAM will also study nucleosynthesis, which explores the formation of atoms more complex than hydrogen. In addition to telling us how isotopes are created in stars, this will allow us study supernova explosions in more depth.

    In addition to the stated science goals, it will also be able to discover new transient sources. These include terrestrial gamma-ray flashes and solar flares. In this manner, e-ASTROGRAM will become tied into the growing field of multimessenger astronomy, where observatories that study different particles (photons, neutrinos, etc.) observe the same source at the same time in order to get a more complete picture of it.

    Detector design

    A drawing showing what e-ASTROGRAM would look like once deployed (figure 19 from the paper)

    he detector itself will look similar to other satellite experiments, but with innovative new design elements. It will consist of three main components. The first is a tracker. Gamma rays will be detectable when they undergo either Compton scattering (the scattering of a photon off a charged particle) or pair conversion (the creation of an electron/positron pair) in the Si strip detectors of the tracker. The second component is a calorimeter will measure the energies of these particles. Lastly, the anti-coincidence system helps separate the gamma rays from the very large backgrounds present in outer space.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 3:13 pm on July 16, 2015 Permalink | Reply
    Tags: , , , Gamma Ray Detection,   

    From ESO: “Paranal Observatory First Choice to Host World’s Largest Array of Gamma-ray Telescopes” 

    European Southern Observatory

    16 July 2015
    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Temp 0

    On 15 and 16 July 2015, the Cherenkov Telescope Array (CTA) Resource Board decided to enter into detailed contract negotiations for hosting the CTA’s southern hemisphere array within the grounds of the Paranal Observatory, one of ESO’s sites in Chile. Similar negotiations for a northern site on La Palma are also starting.

    CTA Array

    The CTA project is an initiative to build the next generation of ground-based instruments designed for the detection of very high energy gamma-rays. Gamma rays are emitted by the hottest and most powerful objects in the Universe — such as supermassive black holes, supernovae and possibly remnants of the Big Bang. The array will provide valuable deeper insights into the high-energy Universe.

    Although gamma rays don’t make it to the Earth’s surface, the CTA’s mirrors and high-speed cameras will capture short-lived flashes of the characteristic eerie blue Cherenkov radiation that is produced when the gamma rays interact with the Earth’s atmosphere. Pinpointing the source of this radiation will allow each gamma ray to be traced back to its cosmic source.

    The CTA Resource Board is composed of representatives of ministries and funding agencies from Austria, Brazil, the Czech Republic, France, Germany, Italy, Namibia, the Netherlands, Japan, Poland, South Africa, Spain, Switzerland and the and the United Kingdom. After months of negotiations and careful consideration of extensive studies of the environmental conditions, simulations of the science performance and assessments of construction and operation costs the Board has decided to start contract negotiations with ESO. The Namibian and Mexican sites will be kept as viable alternatives.

    In order for the CTA to maximise its coverage of the night sky, the array will consist of about 100 telescopes on the Chile site in the southern hemisphere and about 20 telescopes at the northern site.

    The Chile site for the CTA is less than ten kilometres southeast of the location of the Very Large Telescope, within the grounds of ESO’s Paranal Observatory in the Atacama Desert. This is considered one of the driest and most isolated regions on Earth — an astronomical paradise. In addition to the ideal conditions for year-round observation, installing the CTA at the Paranal Observatory offers the CTA the opportunity to take advantage of the existing infrastructure (roads, accommodation, water, electricity, etc.) and access to established facilities and processes for the construction and operation of the telescope array.

    Currently in its pre-construction phase, determination of the array sites is a critical factor in the CTA construction project.

    More Information

    The CTA aims to build the world’s largest and most sensitive high-energy gamma-ray telescope array. Over 1000 scientists and engineers from five continents, 31 countries (Argentina, Armenia, Australia, Austria, Brazil, Bulgaria, Canada, Chile, Croatia, the Czech Republic, Finland, France, Germany, Greece, India, Ireland, Italy, Japan, Mexico, Namibia, the Netherlands, Norway, Poland, Slovenia, South Africa, Spain, Sweden, Switzerland, the United Kingdom, the United States of America and Ukraine) and over 170 research institutes participate in the CTA project. The CTA will serve as an open facility to a wide astrophysics community and provide a deep insight into the non-thermal, high-energy Universe. The CTA will detect high-energy radiation with unprecedented accuracy and approximately ten times the sensitivity of current instruments, providing novel insights into some of the most extreme and violent events in the Universe.

    See the full article here.

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla

    ESO VLT Interferometer

    ESO Vista Telescope

    ESO VLT Survey telescope
    VLT Survey Telescope

    ALMA Array


    Atacama Pathfinder Experiment (APEX) Telescope

  • richardmitnick 8:29 am on July 30, 2014 Permalink | Reply
    Tags: , , , , Gamma Ray Detection,   

    From SPACE.com: “NASA’s Top 10 Gamma-Ray Sources in the Universe” 


    December 06, 2011
    SPACE.com Staff and NASA

    Gamma-rays are the highest-energy form of light in the universe. Some are generated by transient events, such as solar flares and the huge star explosions known as supernovas. Others are produced by steady sources like the supermassive black holes at the hearts of galaxies.

    NASA’s Fermi Gamma-ray Space Telescope has been mapping out the high-energy sky since its June 2008 launch. Earlier this year, the Fermi team released its second catalog of sources detected by the instrument’s Large Area Telescope (LAT), producing an inventory of 1,873 objects shining in gamma-ray light.

    NASA Fermi Telescope

    Fermi scientists recently compiled a “top 10 list” to mark the occasion, and to highlight the diversity of gamma-ray sources. Five of the sources on the list are found within our own Milky Way, while the other five reside in distant galaxies.

    Fermi’s top five sources within our galaxy are:

    1. The Crab Nebula: The famous Crab Nebula, located in the constellation Taurus, is the wreckage of an exploded star whose light reached Earth in 1054. Located 6,500 light-years away, the Crab is one of the most-studied objects in the sky.

    Crab Nebula

    At the heart of an expanding gas cloud lies what’s left of the original star’s core, a super-dense neutron star (also called a pulsar) that spins 30 times per second. Until recently, all of the Crab’s high-energy emissions were thought to be the result of physical processes near the pulsar that tapped into this rapid spin.

    For decades, most astronomers regarded the Crab Nebula as a super-steady beacon at X-ray energies. But data from several orbiting instruments — including Fermi’s Gamma-ray Burst Monitor — now show unexpected variations. Astronomers have demonstrated that since 2008, the nebula has faded by 7 percent at high energies, a reduction likely tied to the environment around its central neutron star.

    Since 2007, Fermi and the Italian Space Agency’s AGILE satellite have detected several short-lived gamma-ray flares at energies hundreds of times higher than the nebula’s observed X-ray variations. In April, the satellites detected two of the most powerful gamma-ray flares yet recorded.

    To account for these “superflares,” scientists say that electrons near the pulsar must be accelerated to energies a thousand trillion times greater than that of visible light. That’s far beyond what can be achieved by the Large Hadron Collider near Geneva, Switzerland, now the most powerful particle accelerator on Earth.

    2. W44:Another interesting supernova remnant detected by Fermi is W44. Thought to be about 20,000 years old — middle-aged for a such a structure — W44 is located 9,800 light-years away in the constellation Aquila.


    The LAT not only detects this W44, it actually reveals super-energetic gamma-rays coming from places where the remnant’s expanding shock wave is known to be interacting with cold, dense gas clouds.

    Such observations are important in solving a long-standing problem in astrophysics: the origin of cosmic rays. Cosmic rays are particles, primarily protons, that move through space at nearly the speed of light. Magnetic fields deflect the particles as they race across the galaxy, and this interaction scrambles their path and masks their origins.

    Scientists can’t say for sure where the highest-energy cosmic rays come from, but they regard supernova remnants as perhaps their likliest origin.

    In 1949, the Fermi telescope’s namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of gas clouds. In the decades that followed, astronomers showed that the magnetic fields in the expanding shock wave of a supernova remnant are just about the best location for this process to work.

    So far, LAT observations of W44 and several other remnants strongly suggest that the gamma-ray emission arises from accelerated protons as they collide with gas atoms.

    3. V407 Cygni: V407 Cygni is a so-called symbiotic binary system — one that contains a compact white dwarf and a red giant star that has swollen to about 500 times the size of the sun.

    V407 Cygni

    V407 Cyni lies about 9,000 light-years away in the constellation Cygnus. The system occasionally flares up when gas from the red giant accumulates on the dwarf’s surface and eventually explodes. This event is sometimes called a nova (after a Latin term meaning “new star”).

    When the system’s most recent eruption occurred in March 2010, Fermi’s LAT surprised many scientists by detecting the nova as a brilliant source. Scientists didn’t expect that this type of outburst had the power to produce high-energy gamma-rays.

    4. Pulsar PSR J0101-6422: Pulsars — rapidly rotating neutron stars — constitute about 6 percent of the new catalog. In some cases the LAT can detect gamma-ray pulses directly, but in many cases pulses were first found at radio wavelengths based on suspicions that a faint LAT source might be a pulsar.

    image of a pulsar

    PSR J0101-6422 is located in the southern constellation of Tucana, its quirky name reflecting its position in the sky.

    The Fermi team originally took notice of the object as a fairly bright but unidentified gamma-ray source in an earlier LAT catalog. Because the distribution of gamma-ray energies in the source resembled what is normally seen in pulsars, radio astronomers in Australia took a look at it using their Parkes radio telescope.

    Pulsars are neutron stars, compact objects packing more mass than the sun’s into a sphere roughly the size of Washington, D.C. Lighthouse-like beams of radiation powered by the pulsar’s rapid rotation and strong magnetic field sweep across the sky with every spin, and astronomers can detect these beams if they happen to sweep toward Earth.

    The Parkes study found radio signals from a pulsar rotating at nearly 400 times a second — comparable to the spin of a kitchen blender — at the same position as the unknown Fermi source. With this information, the LAT team was able to discover that PSR J0101-6422 also blinks in gamma-rays at the same incredible rate.

    5. 2FGL J0359.5+5410: Fermi scientists don’t know what to make of this source, which is located in the constellation Camelopardalis. It resides near the populous midplane of our galaxy, which increases the chance that it’s actually an object in the Milky Way.

    While its gamma-ray spectrum resembles that of a pulsar, pulsations have not been detected, and it isn’t associated with a known object at other wavelengths.

    The top five sources beyond the Milky Way are:

    Centaurs A Galaxy

    Cent A

    1. Centaurus A:The giant elliptical galaxy NGC 5128 is located 12 million light-years away in the southern constellation Centaurus. One of the closest active galaxies, it hosts the bright radio source designated Cen A. Much of the radio emission arises from lobes of gas a million light-years wide, which have been hurled out by the supermassive black hole at the galaxy’s center. [Photos: Black Holes of the Universe]

    Fermi’s LAT detects high-energy gamma-rays from an extended region around the galaxy that corresponds to the radio-emitting lobes. The radio emission comes from fast-moving particles. When a lower-energy photon collides with one of these particles, the photon receives a kick that boosts its energy into the gamma-ray regime.

    It’s a process that sounds more like billiards than astrophysics, but Fermi’s LAT shows that it’s happening in Cen A.
    Our neighboring galaxy, Andromeda, also goes by the names Messier 31 or M31. Here, it is captured in full in this new image by WISE.
    [Pin It] Our neighboring galaxy, Andromeda, also goes by the names Messier 31 or M31. Here, it is captured in full in this new image by WISE.
    Credit: NASA/JPL-Caltech/UCLA
    View full size image

    2. The Andromeda Galaxy (M31): At a distance of 2.5 million light-years, the Andromeda Galaxy is the nearest spiral galaxy to us, one of similar size and structure as our own Milky Way. Easily visible to the naked eye in a dark sky, it’s also a favorite target of sky gazers.


    The LAT team expected to detect M31 because it’s so similar to our own galaxy, which sports a bright band of diffuse emission that creates the most prominent feature in the gamma-ray sky. These gamma-rays are mostly produced when high-energy cosmic rays smash into the gas between stars.

    “It took two years of LAT observations to detect M31,” Jürgen Knödlseder at the Research Institute for Astrophysics and Planetology in Toulouse, France, said in a statement. Currently a visiting scientist at the SLAC National Accelerator Laboratory in California, he worked on the M31 study.

    “We concluded that the Andromeda Galaxy has fewer cosmic rays than our own Milky Way, probably because M31 forms stars — including those that die as supernovae, which help produce cosmic rays —more slowly than our galaxy,” Knödlseder added.

    Hubble M82 Galaxy


    3. The Cigar Galaxy (M82): What works for the Andromeda Galaxy works even better for M82, a so-called starburst galaxy that is also a favorite of amateur astronomers. M82 is located 12 million light-years away in the constellation Ursa Major.

    M82’s central region forms young stars at a rate some 10 times higher than the Milky Way does, activity that also guarantees a high rate of supernovae as the most short-lived stars come to explosive ends.

    Eventually, M82’s superpowered star formation will subside as the gas needed to make new stars is consumed, but that may be tens of millions of years in the future. For now, it’s a bright source of gamma-rays for Fermi.

    4. Blazar PKS 0537-286:

    A blazar

    At the core of an active galaxy is a massive black hole that drives jets of particles moving near the speed of light. Astronomers call the galaxy a blazar when one of these jets is pointed our way — the best view for seeing dramatic flares as conditions change within the jet.

    PKS 0537-286 is a variable blazar in the constellation Leo and the second most distant LAT object. Astronomers have determined that the galaxy lies more than 11.7 billion light-years away.

    The blazar is the farthest active galaxy in the Fermi catalog to show variability. Astronomers are witnessing changes in the jet powered by this galaxy’s supermassive black hole that occurred when the universe was just 2 billion years old (it is now about 13.7 billion years old).

    5. 2FGL J1305.0+1152: The last item is another mystery object, one located in the constellation Virgo and high above our galaxy’s midplane. It remains faint even after two years of LAT observations.

    One clue to classifying these objects lies in their gamma-ray spectrum — that is, the relative number of gamma-rays seen at different energies. At some energy, the spectra of many objects display what astronomers call a “spectral break,” a greater-than-expected drop-off in the number of gamma-rays seen at increasing energies.

    If this object were a pulsar, it would show a fast cutoff at higher energies. Many blazars exhibit much more gradual cutoffs. But 2FGL J1305.0+1152 shows no evidence of a spectral break at all, leaving its nature a true mystery — for now, anyway.

    See the full article here.

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  • richardmitnick 1:47 pm on April 18, 2014 Permalink | Reply
    Tags: , Gamma Ray Detection,   

    From Brookhaven Lab: “The Science of Detecting and Defeating Radiological Threats” 

    Brookhaven Lab

    April 18, 2014
    Kay Cordtz

    If you were at the Super Bowl in New Jersey in February, or at the concurrent “NFL Experience” in Manhattan, you may have spotted some elite Brookhaven Lab employees. Not cheering in the stands or even inside the stadium, these members of the Lab’s Radiological Assistance Program (RAP) team were working on Super Bowl Sunday and for several weeks beforehand to monitor the metropolitan area for potential radiological threats.

    The RAP team, one of the National Nuclear Security Administration’s (NNSA) radiological emergency response assets, is comprised of a few permanent staff, augmented by highly trained volunteers from many Lab disciplines. Together, they work to stay ahead of any such threats using a palette of detection tools that have become increasingly sophisticated and user-friendly, driven by the evolving mission of the program.

    “The whole profile of the team has changed,” said Kathleen McIntyre, who is the contractor operations manager for RAP Region 1, which covers the East Coast from Maine to Maryland and inland to the Pennsylvania-Ohio border. “We used to investigate questionable material found in grandpa’s basement, but since 9/11 the focus has been on search-and-detect missions.”

    Working with first responder partners like the Federal Bureau of Investigation, police and fire departments, hazmat units, Weapons of Mass Destruction Civil Support Teams (Air and Army National Guard), and others, the RAP team offers radiological assistance efforts upon the request of federal, state, tribal, and local governments and private groups and individuals for incidents involving radiological materials. In addition to prominent sporting events, the RAP team supports security efforts for high-profile events like the United Nations General Assembly, New Year’s Eve activities in one or multiple locations, the holiday tree lighting ceremony, the Democratic and Republican national conventions, and even Presidential inaugurations.

    During a deployment, researchers and technicians with backgrounds in various aspects of radiological controls and analysis conduct field monitoring and environmental sampling, assessment, and documentation activities to help decision makers choose appropriate protective actions for the safety of both the public and first responders. Between deployments, the team examines issues of coordination between agencies, plans, and procedures, and trains and evaluates the proficiency of individuals using the equipment. Initially, all RAP team members are required to take a specialized course in Albuquerque, NM, and then attend training sessions at least quarterly. Team members are periodically evaluated through their participation in drills and exercises. Occasionally a “No Notice Exercise” is conducted by NNSA that tests the team’s readiness to respond.
    Advances in equipment

    Although some of the equipment now being used is commercially developed, other instruments are developed specifically for the use of DOE assets such as RAP teams, with the expertise of scientists and engineers from the DOE and NNSA complexes. Lab staff has participated in the development, testing, and functional evaluation of numerous pieces of equipment in this category. The evolution of this equipment conforms to the change in the program’s mission.

    Historically the RAP mission was “consequence management” — events and situations along the lines of responding to a spill from a truck carrying medical radioisotopes, for example. But as the profile of terrorism has been raised across the country and around the world, the need for a more preemptive approach in radiological screening was recognized, and RAP has been increasingly called upon to support law enforcement groups conducting directed or random screening for illicit movement of radiological materials.

    “That screening tends to be correlated with the potential for radiological material to be used to threaten a large mass gathering or other high-profile event,” said Chuck Finfrock, principal engineer for RAP team science. “To assist us in doing what we call low-profile missions, we need to be able to blend into crowds and collect radiological data in the field. Some of the equipment that we originally had was extremely bulky, so scientists have been working on equipment that is easier and less cumbersome to use and allows us to do a quicker assessment of our environment.”

    One of the techniques now being applied to the search and crisis response missions is gamma ray spectroscopy (GRS), largely a laboratory technique used for more than 40 years to identify radiological material. Like a fingerprint, a particular radiological material has a particular gamma ray spectrum that is unique to that radioisotope. As a result, this technique can be used to not only detect the radioactivity of a sample, but also to give information identifying that particular material. The instruments can be very large and are delicate items that need very stable temperature control and a constant supply of liquid nitrogen to cool them.

    One example of a Gamma Ray Sectroscope

    Example of a GRS lab room

    As the RAP program moves to emergency response, more portable equipment allows the team to conduct a search operation with greater focus. For example, a construction site may report a missing soil density gauge – a commercial product containing some radioactive material that’s used to measure the density of compacted soil. With a spectroscopic system, the team knows in advance what isotope they’re seeking and can use GRS to search in a more specific way. Also, while the older GRS systems always required a human to take, calibrate, and analyze the data, computer software can now automate some analysis of that gamma ray spectral information.

    “The instruments are also, in effect, becoming ‘smarter’ and better able to help first responder partners with limited knowledge collect the initial on-scene information. This improves the quality of the data collected, which in turn helps a team scientist to understand the event more quickly,” said McIntyre. “Another important technological change that’s taking place is that instruments are being equipped with the ability to communicate by cell phone, satellite or Wi-Fi, allowing us to send data from the field back to a command center in near real time. Operators in the field working in multiple locations can send data back to the command center to be analyzed by one specialist at the command center.”

    Portable GRS Unit

    Other new, more sophisticated algorithms can generate data products, such as maps, at different stages of an event, so technical information can be conveyed to decision makers at a glance.
    Training, teamwork critical

    But McIntyre warns that as sophisticated and user friendly that this gear has become, “we cannot emphasize enough how important it is to have an individual who has proficiency in the equipment that is being deployed in the field. Some of the first responders wear many hats, and while they do receive training, they don’t have the kind of in-depth knowledge and access to scientific expertise that members of the RAP team have. There are still important issues related to the fact that we live in a sea of radiation from rocks and soil. Also, we live in a community where radiological materials are used in many medical applications. As an example, we often encounter people who have had a thallium stress test or other medical administration. That person will measure as radioactive for days or weeks.”

    “Construction materials can also offer challenges,” she added. “On the streets of New York City, you’ll see great changes in the background radiation levels as you go from avenue to avenue and street to street. Our team has been trained to be cognizant of those changes and those contributing factors as well as being on high alert for something that might contribute additional information that might be of interest.”

    The context surrounding a measurement needs to be evaluated by someone with some understanding of the world’s background radiation footprint. The DOE community also has a capability called TRIAGE, where highly trained specialists from the NNSA nuclear weapons laboratories provide a scientific confirmation of the measurements made in the field. Advances in equipment communication allow that information to be communicated to specialists who can analyze field measurements that may look ambiguous.

    “The evolution of our capabilities is a combination of advancements in different areas,” Finfrock said “The advancements in detector engineering have caused them to become more field-usable. The advances in communications electronics and computers have enabled the detectors to more easily send data to the right people quickly. Most detectors now have global positioning tagged in with the radiological data, so not only are we getting back radiological measurements but we also know very precisely where that measurement was taken. We can correlate multiple measurements in multiple locations to be able to anticipate situations because we have geospatial awareness as well as radiological awareness.”

    As the radiological landscape continues to evolve, both in this country and abroad, the RAP team and others will continue to refine their search and detection techniques, and scientists at Brookhaven Lab and elsewhere will be working to stay ahead of the technology curve.

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

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