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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Abstract : Gamma-ray astronomy is the study of very energetic photons, from E = mec2 = 0.5x106 eV to > 10 1020eV. Due to the large span of the energy range, the field focuses on non-thermal processes that include the acceleration and propagation of relativistic particles, which can be found in extreme environments such as pulsars, supernova remnants, molecular clouds, black holes, etc. The High Altitude Water Cherenkov (HAWC) observatory is an instrument designed for the study of gamma rays in the energy range of 100 GeV to 100 TeV. Using data from the HAWC observatory, a study for the search of very high energy gamma rays in the northern Fermi Bubble region was made. The Fermi Bubbles are large extended regions in the gamma-ray sky located above and below the galactic plane that present a hard emission between 1 GeV and 100 GeV. No significant excess is found an upper bounds at 95% C.L. are obtained. The implications of this result are that certain processes explaining the Fermi Bubble formation from the center of our galaxy are excluded. I will discuss and compare the scenarios that still present a possible hypothesis of the Fermi Bubble origin.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Abstract : Gamma-ray astronomy is the study of very energetic photons, from E = mec2 = 0.5x106 eV to > 10 1020eV. Due to the large span of the energy range, the field focuses on non-thermal processes that include the acceleration and propagation of relativistic particles, which can be found in extreme environments such as pulsars, supernova remnants, molecular clouds, black holes, etc. The High Altitude Water Cherenkov (HAWC) observatory is an instrument designed for the study of gamma rays in the energy range of 100 GeV to 100 TeV. Using data from the HAWC observatory, a study for the search of very high energy gamma rays in the northern Fermi Bubble region was made. The Fermi Bubbles are large extended regions in the gamma-ray sky located above and below the galactic plane that present a hard emission between 1 GeV and 100 GeV. No significant excess is found an upper bounds at 95% C.L. are obtained. The implications of this result are that certain processes explaining the Fermi Bubble formation from the center of our galaxy are excluded. I will discuss and compare the scenarios that still present a possible hypothesis of the Fermi Bubble origin.
Author: Matthew Rosenberg Publisher: ISBN: Category : Languages : en Pages :
Book Description
Gamma-Ray Bursts (GRBs) are brief, intense flashes of gamma rays lasting from a fraction of a second to minutes. The prompt emission from these explosive events outshines all the stars in their entire host galaxy. Thought to be produced by the core collapse of massive stars and the merger of compact stellar remnants in distant galaxies, GRBs can liberate on the order of 10^54 ergs of gravitational potential energy in just milliseconds. In addition to constituting an interesting phenomenon in their own right, these cosmic engines accelerate particles to energy scales unattainable in laboratories on Earth and thus provide a potentially interesting probe of fundamental physics as well as source candidates for ultra-high energy cosmic rays. We present recent efforts to extend the observation of GRBs beyond ~100 GeV with the High Altitude Water Cherenkov (HAWC) observatory. Located in Puebla, Mexico at a latitude of 19 degrees north and an altitude of 4100 meters above sea level, HAWC employs a 20,000 square meter array of 300 water Cherenkov detectors to observe the relativistic charged particles produced in the extensive air showers that develop upon the collision of high-energy gamma rays with Earths atmosphere. This technique provides sensitivity to ~100 GeV 100 TeV gamma rays, allows for nearly continuous operations, and achieves a wide instantaneous field of view of ~2 sr that allows for daily monitoring of the northern sky. HAWC is thus ideally suited to capture any emission above ~100 GeV from transient events like GRBs. As GRB photons above a few TeV in energy are likely to be absorbed by the extra-galactic background light before reaching Earth, HAWCs ~100 GeV 1 TeV data is of prime importance in the search for high-energy GRB emission. However, the small air-shower data necessary to achieve this lower threshold of ~100 GeV has previously been poorly modeled in HAWC simulations and has therefore not been used in past HAWC GRB searches. We will show that these modeling discrepancies were caused by an inaccurate treatment of detector noise, outline a solution that allows HAWC to achieve its lowest possible energy threshold, and present a method to reduce the impact of detector noise on HAWCs angular resolution in this newly recovered small air-shower data. Along with new GRB search algorithms, these improvements provide up to an order of magnitude improvement in HAWCs sensitivity to gamma-ray bursts. We use these new techniques to scan archival HAWC data for gamma-ray emission coincident with GRBs detected by the Fermi and Swift satellites between December 2014 and April 2018. While no significant detections were found, a comparison of our upper limits on the flux above 100 GeV from GRBs 170206A and 171120A with Fermi measurements suggests a cut-off or spectral steepening below that energy under a redshift assumption of z less than ~0.3. However, these limits are not sufficiently strict to compellingly constrain GRB models with predictions for TeV scale gamma-ray emission.
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: Alison Peisker Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 152
Book Description
The universe contains many extremely energetic astrophysical sources that emit particles on timescales from fractions of a second to thousands of years. Studying these sources through gamma-ray and multi-messenger astronomy may help to reveal the answers to several remaining fundamental questions in physics. The High Altitude Water Cherenkov (HAWC) gamma-ray observatory, an extensive air shower array, is well-suited to perform transient searches due to its large field of view and high duty cycle. In this work, a catalog search of all very-high-energy gamma-ray sources in HAWC's field of view is conducted, revealing a total of 65 sources. Then a search for evaporating primordial black holes is performed. None are detected, so upper limits are set on their burst rate density. Finally, the IceCube neutrino observatory is introduced in order to perform a multi-messenger search for flaring gamma rays and neutrinos originating from the same point in the sky. None are detected, so upper limits are placed on the rate density and total energy of sources that produce both gamma rays and neutrinos. Performing these searches contributes to the understanding of the origins of cosmic rays and how astrophysical sources accelerate their particles to the high energies that are observed on Earth.
Author: Kathryne Woodle Publisher: ISBN: Category : Languages : en Pages :
Book Description
Gamma-Ray bursts (GRBs) are extremely powerful transient events that occur at cosmological distances. Observations of energy spectra of GRBs can provide information about the intervening space between the burst and Earth as well as about the source itself. GRBs have been observed up to nearly 100 GeV by satellite instruments; however, ground-based detectors are needed to provide enough exposure and statistics to determine the behavior of GRBs at those energies. The High Altitude Water Cherenkov Observatory (HAWC) is a second-generation extensive air shower detector that primarily observes very high-energy (VHE) photons, where VHE is defined as hundreds of GeV to hundreds of TeV. HAWC is built near the peak of Sierra Negra in Mexico at an altitude of 4100m. The high altitude allows the detector to observe air showers when more information is available for reconstruction. Due to its wide field of view (~2 sr) and high duty cycle (>90%), the HAWC observatory is sensitive to gamma rays in the sub-TeV to TeV energy range and can constrain the shape and cutoff of high-energy GRB spectra, especially in conjunction with observations from other detectors such as the Fermi LAT satellite. We present a likelihood-based search for VHE emission from the Fermi LAT GRBs that occurred in the field of view of HAWC during the last two years of its construction. Of the five bursts analyzed, no significant detections were observed; upper limits have been placed for each of the bursts. With less than 1/3 of the array active, the HAWC observatory limits for GRB 130702A, which is at a close redshift of z = 0.145, reach comparable sensitivity to lower energy instruments and are not limited by the EBL. With the array complete in March 2015, the sensitivity of HAWC is now greatly enhanced compared to the data analyzed in this dissertation. The future for a VHE GRB detetion by the HAWC observatory is bright.
Author: Kenya Aonye Mitchell Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
In January of 2021, the HAWC observatory released their third catalogue of very-high-energy gamma ray sources. In this catalogue, 20 of the 65 sources were labeled unassociated. Meaning of all previously discovered sources, they have no high energy counterpart within 1°. From these 20 sources, it was seen that three sources 3HWC J0621+382, 3HWC J0631+107, and 3HWC J1739+099 were closely associated with pulsars PSR J0622+3749, PSR J0631+1036, and PSR J1740+100 respectively. These pulsars are listed in the ANTF pulsar catalog. It is important that these three sources be further studied, as the pulsar association can give clues regarding the origin of gamma ray acceleration. To expand the investigation of these sources, a morphological and spectral analysis was conducted to determine changes in each source's extension and level of emission. Comparisons between pulsar data and HAWC data were also conducted to verify that each experiment was seeing the same thing. Multiple software packages were utilized to visualize the data. The Multi-Mission Maximum Likelihood framework (3ML) in conjunction with the HAWC accelerated likelihood (HAL) plugin is used to fit source spectrums and determine morphology. After analyzing data from HAWC's datasets of 1,523 days and 2,770 days, it was concluded that each source exhibited significant growth in intensity over time. Future work will include a multi-wavelength analysis using data from other gamma-ray experiments.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
In 2010, the Fermi Bubbles were discovered at the galactic center of the Milky Way. These giant gamma-ray structures, extending 55° in galactic latitude and 20°-30° in galactic longitude, were not predicted. We wish to develop a model for the gamma-ray emission of the Fermi Bubbles. To do so, we assume that second order Fermi acceleration requires charged particles and irregular magnetic fields- both of which are present in the disk of the Milky Way galaxy. By solving the steady-state case of the transport equation, I compute the proton spectrum due to second order Fermi acceleration. I compare the analytical solutions of the proton spectrum to a numerical solution. I find that the numerical solution to the transport equation converges to the analytical solution in all cases. The gamma-ray spectrum due to proton-proton interaction is compared to Fermi Bubble data (from Ackermann et al. 2014), and I find that second order Fermi acceleration is a good fit for the gamma-ray spectrum of the Fermi Bubbles at low energies with an injection source term of S = 1.5 x 10−10 GeV−1cm−3yr−1. I find that a non-steady-state solution to the gamma-ray spectrum with an injection source term of S = 2 x 10−10 GeV−1cm−3yr−1 matches the bubble data at high energies.
Author: Marco Maria Massai Publisher: World Scientific ISBN: 9814474495 Category : Science Languages : en Pages : 251
Book Description
The research program in gamma-ray astronomy focuses on increasing our knowledge of the nature and origin of galactic and extragalactic gamma rays, and understanding high-energy processes in the Sun, celestial objects, interstellar medium, and extragalactic space.This book not only provides an overview of the latest research and future plans for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky, but also addresses the topic of variable gamma-ray sources from the perspective of their identification and counterparts at different wavelengths. It further gives an overview of the theory related to the most qualified emission processes that take place in these sources and of the nature of their variability.
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Author: Matthew Rosenberg
Author: Pierre Sokolsky
Author: Alison Peisker
Author: Kathryne Woodle
Author: Kenya Aonye Mitchell
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Author: Marco Maria Massai
Author: Richard Schnee
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