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  • richardmitnick 9:07 am on October 8, 2016 Permalink | Reply
    Tags: , , , , , , , VERITAS Gamma Ray Telescope   

    From IceCube: “Neutrinos and gamma rays, a partnership to explore the extreme universe” 

    icecube
    IceCube South Pole Neutrino Observatory

    07 Oct 2016
    Sílvia Bravo

    Solving the mystery of the origin of cosmic rays will not happen with a “one-experiment show.” High-energy neutrinos might be produced by galactic supernova remnants or by active galactic nuclei as well as other potential sources that are being sought. And, if our models are right, gamma rays at lower energies could also help identify neutrino sources and, thus, cosmic-ray sources. It’s sort of a “catch one, get them all” opportunity.

    IceCube’s collaborative efforts with gamma-ray, X-ray, and optical telescopes started long ago. Now, the IceCube, MAGIC and VERITAS collaborations present updates to their follow-up programs that will allow the gamma-ray community to collect data from specific sources during periods when IceCube detects a higher number of neutrinos.

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

    CfA/VERITAS, AZ, USA
    “CfA/VERITAS, AZ, USA

    Details of the very high energy gamma-ray follow-up program have been submitted to the Journal of Instrumentation.

    1
    Image: Juan Antonio Aguilar and Jamie Yang. IceCube/WIPAC

    From efforts begun by its predecessor AMANDA, IceCube initiated a gamma-ray follow-up program with MAGIC for sources of electromagnetic radiation emissions with large time variations. If we can identify periods of increased neutrino emission, then we can look for gamma-ray emission later on from the same direction.

    For short transient sources, such as gamma-ray bursts and core-collapse supernovas, X-ray and optical wavelength telescopes might also detect the associated electromagnetic radiation. In this case, follow-up observations are much more time sensitive, with electromagnetic radiation expected only a few hours after neutrino emission from a GRB or a few weeks after a core-collapse supernova.

    Updates to this transient follow-up system will use a multistep high-energy neutrino selection to send alerts to gamma-ray telescopes, such as MAGIC and VERITAS, if clusters of neutrinos are observed from a predefined list of potential sources. The combined observation of an increased neutrino and gamma-ray flux could point us to the first source of astrophysical neutrinos. Also, the information provided by both cosmic messengers will improve our understanding of the physical processes that power those sources.

    The initial selection used simple cuts on a number of variables to discriminate between neutrinos and the atmospheric muon background. IceCube, MAGIC, and VERITAS are currently testing a new event selection that uses learning machines and other sophisticated discrimination algorithms to take into account the geometry and time evolution of the hit pattern in IceCube events. Preliminary studies show that this advanced event selection has a sensitivity comparable to offline point-source samples, with a 30-40% sensitivity increase in the Northern Hemisphere with respect to the old selection. The new technique does not rely only on catalogues of sources and allows observing neutrino flares in the Southern Hemisphere. Thus, those alerts will also be forwarded to the H.E.S.S. collaboration, expanding the gamma-ray follow-up program to the entire sky.

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

    During the last few years, IceCube has sent several alerts to VERITAS and MAGIC that have not yet resulted in any significant correlation between neutrino and gamma-ray emission. For some of those, however, the source was not in the reach of the gamma-ray telescopes, either because it was out of the field of view or due to poor weather conditions. Follow-up studies have allowed setting new limits on high-energy gamma-ray emission.

    With the increased sensitivity in the Northern Hemisphere and new alerts to telescopes in the Southern Hemisphere, the discovery potential of these joint searches for neutrino and gamma-ray sources is greatly enhanced. Stay tuned for new results!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ICECUBE neutrino detector

    IceCube neutrino detector interior

    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 2:04 pm on December 15, 2015 Permalink | Reply
    Tags: , , , , , VERITAS Gamma Ray Telescope   

    From CfA: “VERITAS Detects Gamma Rays from Galaxy Halfway Across the Visible Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    December 15, 2015
    Christine Pulliam
    Media Relations Manager
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu – See more at: https://www.cfa.harvard.edu/news/2015-29#sthash.X9b3ENBu.dpuf

    1

    In April 2015, after traveling for about half the age of the universe, a flood of powerful gamma rays from a distant galaxy slammed into Earth’s atmosphere. That torrent generated a cascade of light – a shower that fell onto the waiting mirrors of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona.

    CfA VERITAS
    VERITAS Gamma Ray telescope array

    The resulting data have given astronomers a unique look into that faraway galaxy and the black hole engine at its heart.

    Gamma rays are photons of light with very high energies. These gamma rays came from a galaxy known as PKS 1441+25, which is a rare type of galaxy known as a blazar. At its center it hosts a supermassive black hole surrounded by a disk of hot gas and dust.

    As material from the disk swirls toward the black hole, some of it gets channeled into twin jets that blast outward like water from a fire hose only much faster – close to the speed of light. One of those jets is aimed nearly in our direction, giving us a view straight into the galaxy’s core.

    “We’re looking down the barrel of this relativistic jet,” explains Wystan Benbow of the Harvard-Smithsonian Center for Astrophysics (CfA). “That’s why we’re able to see the gamma rays at all.”

    One of the unknowns in blazar physics is the exact location of gamma-ray emission. Using data from VERITAS, as well as the Fermi Gamma-Ray Space Telescope, the researchers found that the source of the gamma rays was within the relativistic jet but surprisingly far from the galaxy’s black hole.

    NASA Fermi Telescope
    NASA/Fermi

    The emitting region is at least a tenth of a light-year away, and most likely is 5 light-years away. (A light-year is the distance light travels in one year, or about 6 trillion miles.)

    Moreover, the region emitting gamma rays was larger than typically seen in an active galaxy, measuring about a third of a light-year across.

    “These jets tend to have clumps in them. It’s possible that two of those clumps may have collided and that’s what generated the burst of energy,” says co-author Matteo Cerruti of the CfA.

    Measuring high-energy gamma rays at all was a surprise. They tend to be either absorbed at the source or on their long journey to Earth. When the galaxy flared to life, it must have generated a huge flood of gamma rays.

    The finding also provides insight into a phenomenon known as extragalactic background light or EBL, a faint haze of light that suffuses the universe. The EBL comes from all the stars and galaxies that have ever existed, and in a sense can track the history of the universe.

    The EBL also acts like a fog to high-energy gamma rays, absorbing them as they travel through space. This new measurement sets an indirect limit on how abundant the EBL can be – too much, and it would have absorbed the gamma-ray flare. The results complement previous measurements based on direct observations.

    These results have been accepted for publication in The Astrophysical Journal Letters and are available online.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 11:32 am on February 28, 2014 Permalink | Reply
    Tags: , , , , , VERITAS Gamma Ray Telescope   

    From S.A.O. : “An Extended Gamma-Ray Source with No Known Counterpart” 

    Smithsonian Astrophysical Observatory

    February 28, 2014
    No Writer Credit

    A look at CfA discoveries from recent journals

    Gamma-rays are the most energetic known form of electromagnetic radiation, with each gamma ray being at least one hundred thousand times more energetic than an optical light photon. The most potent gamma rays, the so-called VHE (very high energy) gamma rays, pack energies a billion times this amount, or even more. Astronomers think that VHE gamma rays are produced in the environment of the winds or jets of the compact, ultra-dense remnant ashes of massive stars left behind from supernova explosions.

    There are two kinds of compact objects produced in supernovae: black holes and neutron stars (stars made up predominantly of neutrons, having densities equivalent to the mass of the Sun packed into a volume about 10 kilometers in radius). The winds or jets from the environments of such objects, including the kind called pulsars, can accelerate charged particles to very close to the speed of light. When light scatters off such energetic particles it becomes energized as well, sometimes turning into VHE gamma rays. At least this is the most popular current theory. One of the first known VHE sources was spotted about fifteen years ago in the direction of the constellation of Cygnus. It was unusual because, unlike most other known VHE sources which had counterparts seen at optical, radio, or other wavelengths, this new source had no known counterpart. With no other information available, its exact nature was mysterious.

    Recently a pulsar was discovered in the general vicinity, renewing interest in the source. CfA astronomers Wystan Benbow, Matteo Cerruti, Pascal Fortin, Nicola Galante, Emmet Thomas, and Trevor Weekes along with a large team of colleagues tackled the puzzle using the VERITAS gamma-ray telescope at the Fred L. Whipple Observatory in Arizona. They obtained very long, sensitive observations of the VHE source in Cygnus, and for the first time were able to refine the location and to determine that the emission was not point-like but slightly extended and asymmetric in shape. The astronomers conclude for several reasons that the newly found pulsar is probably not the origin of the VHE emission.

    Veritas Telescope
    VERITAS

    Remarkably, even with the refined location, images at other wavelengths reveal no point sources. In the infrared images, however, the region can be characterized by the fact that it lacks any dust emission and so appears dark while its surroundings glow with cool dust emission. The dark region is very nearly the same shape as the gamma-ray region, making the source even more mysterious than before. However, if the object were a faint pulsar whose wind produced VHE gamma-rays, it might, in some scenarios, also have blown away all the local dust to clear a void like the one seen in the infrared. More work is needed to understand this intriguing object but the current work, with its sensitivity and spatial resolution results, represents an important advance in the field of gamma-ray astronomy.

    See the full article here.
    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.


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