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Author: Nicole Firestone Publisher: ISBN: Category : Languages : en Pages :
Book Description
As neutrally-charged astrophysical messengers, gamma rays serve as powerful tools for determining the origins of incredibly high-energy particles from across our universe [1]. Gamma rays are considered to have the highest energy of all electromagnetic radiation, with energies spanning from 0.5 MeV to about 100 TeV [2]. Although lower-energy gamma rays can originate from within our solar system, gamma rays in the GeV and TeV ranges tend to originate from sources beyond our solar system [1]. By investigating these sources, we can understand more about the astrophysical phenomena that characterize the most extreme conditions in our universe, such as supernova remnants, gamma-ray bursts, and pulsars [3]. The High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) is one of the most sensitive gamma-ray detectors in the very high energy (VHE) regime, with the capability to observe gamma rays from 100 GeV and 100 TeV [4]. In 2017, HAWC conducted a blind search encompassing two thirds of the sky and 508 days of observations [4]. In this search, there were 16 VHE gamma-ray excesses that were unassociated with any previously discovered gamma-ray sources [4]. Now with data from 1523 days of observations, we begin to study these 16 unassociated candidate TeV sources in more detail. In this work, we update the locations of maximum significance for these candidate TeV sources and analyze the temporal progression of their significance and flux. This allows us to determine if they have faded into the diffuse gamma radiation or if they can still be considered unassociated candidate TeV sources. We then reevaluate the morphologies and spectral energy distributions of the remaining sources and discuss any recent observations from other gamma-ray observatories. We find that 10 of these 16 unassociated candidate TeV sources can still be considered candidate sources. In the future, we plan to use data from other observatories to continue to put better constrains on the morphology and spectral energy distributions for these sources and better understand their acceleration mechanisms. In addition, we plan to conduct a similar investigation with new HAWC excesses discovered with recent data from 1523 days of observations [5]. By investigating these excesses in the high-energy gamma-ray sky, we can discover and characterize new extreme astrophysical phenomena and ultimately uncover valuable information about the physical mechanisms that accelerate particles to very high energies.
Author: Nicole Firestone Publisher: ISBN: Category : Languages : en Pages :
Book Description
As neutrally-charged astrophysical messengers, gamma rays serve as powerful tools for determining the origins of incredibly high-energy particles from across our universe [1]. Gamma rays are considered to have the highest energy of all electromagnetic radiation, with energies spanning from 0.5 MeV to about 100 TeV [2]. Although lower-energy gamma rays can originate from within our solar system, gamma rays in the GeV and TeV ranges tend to originate from sources beyond our solar system [1]. By investigating these sources, we can understand more about the astrophysical phenomena that characterize the most extreme conditions in our universe, such as supernova remnants, gamma-ray bursts, and pulsars [3]. The High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) is one of the most sensitive gamma-ray detectors in the very high energy (VHE) regime, with the capability to observe gamma rays from 100 GeV and 100 TeV [4]. In 2017, HAWC conducted a blind search encompassing two thirds of the sky and 508 days of observations [4]. In this search, there were 16 VHE gamma-ray excesses that were unassociated with any previously discovered gamma-ray sources [4]. Now with data from 1523 days of observations, we begin to study these 16 unassociated candidate TeV sources in more detail. In this work, we update the locations of maximum significance for these candidate TeV sources and analyze the temporal progression of their significance and flux. This allows us to determine if they have faded into the diffuse gamma radiation or if they can still be considered unassociated candidate TeV sources. We then reevaluate the morphologies and spectral energy distributions of the remaining sources and discuss any recent observations from other gamma-ray observatories. We find that 10 of these 16 unassociated candidate TeV sources can still be considered candidate sources. In the future, we plan to use data from other observatories to continue to put better constrains on the morphology and spectral energy distributions for these sources and better understand their acceleration mechanisms. In addition, we plan to conduct a similar investigation with new HAWC excesses discovered with recent data from 1523 days of observations [5]. By investigating these excesses in the high-energy gamma-ray sky, we can discover and characterize new extreme astrophysical phenomena and ultimately uncover valuable information about the physical mechanisms that accelerate particles to very high energies.
Author: Erica Heller Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Only three sources of extragalactic TeV gamma-ray emission have been observed by the High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. Using a pre-selected candidate list of potential TeV-emitting BL Lac objects, we searched for TeV emission using the 2321-day dataset from the HAWC Observatory. Eleven BL Lac objects were investigated. For four of these BL Lac objects, lower energy gamma-ray data was available from the Fermi Large Area Telescope (Fermi-LAT). Using data from Fermi-LAT, we fit a simple power law model to the energy spectrum of each source and used this simple power law model to investigate the region using HAWC. We found no significant TeV gamma-ray emission from these four sources. We set upper limits on the flux from these sources at 1 TeV. For the remaining seven sources, we used three simple power law models due to the lack of lower-energy gamma-ray data. We found no significant TeV gamma-ray emission from these seven sources using all three simple power law models, and we set upper limits on the flux from these sources at 1 TeV for each model. Despite the lack of gamma-ray detection from these sources, we determine that the upper limits set using HAWC data can constrain the extrapolation of a simple power law model into the TeV energy range for three of the four sources with Fermi-LAT data. Through these investigations of BL Lac objects, we provide valuable information about the acceleration mechanisms occurring at these extreme extragalactic objects.
Author: Zigfried Hampel-Arias Publisher: ISBN: Category : Languages : en Pages : 346
Book Description
Over the past two decades, a more detailed understanding of TeV-scale cosmic rays has emerged which appears to deviate from the isotropic, single power law description of the cosmic ray flux. This may be the result of the distribution of sources within the Galaxy, changes in source spectra, effects from the propagation of cosmic rays from their sources to Earth, or a combination of the three. Supernova remnants are thought to be the most likely source of Galactic cosmic rays, providing a natural power law source spectrum with sufficient power to generate the observed cosmic ray energy density. Yet, recent results from balloon-borne experiments hint at a possible change in the spectral index between 20−50 TeV. These direct detection apparatuses provide the most precise measurements of the cosmic ray flux up to ~30 TeV, beyond which they are limited by the combined effects of their physical dimensions, runtime durations, and a rapidly decreasing flux. Above ~100 TeV, the spectrum has been measured by ground based air shower arrays, with typical systematic uncertainties of order 10%. Despite having the combined measurements from various experimental techniques, their different energy scales and systematics imply that identifying finer structure between 10−100 TeV requires a single experimental method to span the entire range. Furthermore, as the nearest potential source is hundreds of parsecs away and the Larmor radius of TeV scale charged cosmic rays in the Galaxy is of order 10−3 parsecs, the previously observed anisotropy in arrival directions of cosmic rays is unexpected. In order to attain the statistical power necessary to observe TeV cosmic ray anisotropy at the 10−3 level and below, the long data taking periods required are only attainable by air shower arrays. This thesis presents a measurement of the cosmic ray energy spectrum and the energy dependence of the anisotropy on small scales O(10°) using data from the High Altitude Water Cherenkov (HAWC) Observatory, an air-shower array located near Puebla, Mexico that is sensitive to gamma rays and cosmic rays at TeV energies. The analyses in this work comprise data taking periods of order 1 yr containing ~1010 events. An analysis of the cosmic ray Moon shadow is first presented as a verification of the angular resolution and energy scale of the detector. Next, a measurement of the all-particle cosmic ray energy spectrum from 10−500 TeV is shown, with an indication of structure deviating from a single power law. The final results presented in this work show an improved spectral measurement of a particular region of cosmic ray excess at the 10−4 level, previously observed both in HAWC and in other experiments.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Over the past two decades, ground-based measurements of the arrival directions of TeV cosmic rays have revealed an unexpected anisotropy. Multiple detectors have recorded fluxes above all-sky averages to high statistical significance for features at large (about 180°) and small (about 5°) angular sizes. Likely sources of high-energy cosmic rays are no closer than about 100 pc, about 100,000 Larmor radii for a TeV proton in typical interstellar magnetic fields of order several microGauss. This thesis outlines methods to search for signals in cosmic-ray arrival directions on data from the High-Altitude Water Cherenkov (HAWC) Observatory -- an extended air shower detector array in Puebla, Mexico, sensitive to gamma rays and cosmic rays at TeV energies. The detector is currently under construction, but data acquisition with the partially deployed detector started in 2013. An analysis of the cosmic-ray arrival direction distribution based on 86 billion events recorded between June 2013 and July 2014 shows anisotropy at the 10^(-4) level on angular scales of about 10°. The HAWC cosmic-ray sky map exhibits three regions of significantly enhanced cosmic-ray flux; two of these regions were first reported by the Milagro experiment. A third region coincides with an excess recently reported by the ARGO-YBJ experiment. An angular power spectrum analysis of the sky shows that all terms up to l=15 contribute significantly to the excesses. Large angular scales (>60°) are also considered, but the results are still preliminary as they are contaminated with non-sidereal signals which cancel for integer years of continuous data. An analysis of the cosmic-ray Moon shadow is shown to demonstrate the angular resolution and energy scale of the data set and to evaluate part of the analysis technique.
Author: Pierre Sokolsky Publisher: World Scientific ISBN: 1800612621 Category : Science Languages : en Pages : 323
Book Description
The universe is pervaded by particles with extreme energies, millions of times greater than we can produce on Earth. They have been a mystery for over a century. Now, current and future experiments in particle astrophysics are leading us to answers to the most fundamental questions about them. How does nature accelerate the highest energy particles in the universe? Do new interactions between them occur at such extreme energies? Are there unknown aspects of spacetime that can be uncovered by studying these particles?This book brings together three fields within 'extreme astronomy': ultra-high-energy cosmic ray physics, neutrino astronomy, and gamma-ray astronomy, and discusses how each can help answer these questions. Each field is presented with a theoretical introduction that clearly elucidates the key questions scientists face. This is followed by chapters that discuss the current set of experiments — how they work and their discoveries. Finally, new techniques and approaches are discussed to solve the mysteries uncovered by the current experiments.
Author: The Cta Consortium Publisher: World Scientific ISBN: 9813270101 Category : Science Languages : en Pages : 365
Book Description
This book summarizes the science to be carried out by the upcoming Cherenkov Telescope Array, a major ground-based gamma-ray observatory that will be constructed over the next six to eight years. The major scientific themes, as well as core program of key science projects, have been developed by the CTA Consortium, a collaboration of scientists from many institutions worldwide.CTA will be the major facility in high-energy and very high-energy photon astronomy over the next decade and beyond. CTA will have capabilities well beyond past and present observatories. Thus, CTA's science program is expected to be rich and broad and will complement other major multiwavelength and multimessenger facilities. This book is intended to be the primary resource for the science case for CTA and it thus will be of great interest to the broader physics and astronomy communities. The electronic version (e-book) is available in open access.
Author: Felix Aharonian Publisher: Springer Science & Business Media ISBN: 364236134X Category : Science Languages : en Pages : 369
Book Description
With the success of Cherenkov Astronomy and more recently with the launch of NASA’s Fermi mission, very-high-energy astrophysics has undergone a revolution in the last years. This book provides three comprehensive and up-to-date reviews of the recent advances in gamma-ray astrophysics and of multi-messenger astronomy. Felix Aharonian and Charles Dermer address our current knowledge on the sources of GeV and TeV photons, gleaned from the precise measurements made by the new instrumentation. Lars Bergström presents the challenges and prospects of astro-particle physics with a particular emphasis on the detection of dark matter candidates. The topics covered by the 40th Saas-Fee Course present the capabilities of current instrumentation and the physics at play in sources of very-high-energy radiation to students and researchers alike. This book will encourage and prepare readers for using space and ground-based gamma-ray observatories, as well as neutrino and other multi-messenger detectors.
Author: Roberto Aloisio Publisher: Springer ISBN: 331965425X Category : Science Languages : en Pages : 554
Book Description
This book, designed as a tool for young researchers and graduate students, reviews the main open problems and research lines in various fields of astroparticle physics: cosmic rays, gamma rays, neutrinos, cosmology, and gravitational physics. The opening section discusses cosmic rays of both galactic and extragalactic origin, examining experimental results, theoretical models, and possible future developments. The basics of gamma-ray astronomy are then described, including the detection methods and techniques. Galactic and extragalactic aspects of the field are addressed in the light of recent discoveries with space-borne and ground-based detectors. The review of neutrinos outlines the status of the investigations of neutrino radiation and brings together relevant formulae, estimations, and background information. Three complementary issues in cosmology are examined: observable predictions of inflation in the early universe, effects of dark energy/modified gravity in the large-scale structure of the universe, and neutrinos in cosmology and large-scale structures. The closing section on gravitational physics reviews issues relating to quantum gravity, atomic precision tests, space-based experiments, the strong field regime, gravitational waves, multi-messengers, and alternative theories of gravity.
Author: Luciano Rezzolla Publisher: Springer ISBN: 3319976168 Category : Science Languages : en Pages : 811
Book Description
This book summarizes the recent progress in the physics and astrophysics of neutron stars and, most importantly, it identifies and develops effective strategies to explore, both theoretically and observationally, the many remaining open questions in the field. Because of its significance in the solution of many fundamental questions in nuclear physics, astrophysics and gravitational physics, the study of neutron stars has seen enormous progress over the last years and has been very successful in improving our understanding in these fascinating compact objects. The book addresses a wide spectrum of readers, from students to senior researchers. Thirteen chapters written by internationally renowned experts offer a thorough overview of the various facets of this interdisciplinary science, from neutron star formation in supernovae, pulsars, equations of state super dense matter, gravitational wave emission, to alternative theories of gravity. The book was initiated by the European Cooperation in Science and Technology (COST) Action MP1304 “Exploring fundamental physics with compact stars” (NewCompStar).
Author: Nicole Firestone
Author: Nicole Firestone
Author: Erica Heller
Author: Zigfried Hampel-Arias
Author: 
Author: Pierre Sokolsky
Author: 
Author: The Cta Consortium
Author: Felix Aharonian
Author: Roberto Aloisio
Author: Luciano Rezzolla