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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: 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: Chang Dong Rho Publisher: ISBN: Category : Languages : en Pages : 204
Book Description
"Astrophysical sources of very-high-energy (VHE) gamma-ray radiation provide unique information about astrophysical particle acceleration and cosmic-ray production. In particular, compact binary systems, composed of a compact object (a neutron star or black hole) in orbit with a massive stellar companion, provide an ideal environment for VHE gamma-ray production. They are not only powerful particle accelerators, but they also exhibit periodic emission that makes them excellent astrophysical laboratories. However, only a handful of binary systems have ever been observed in VHE gamma rays. Partly, this is because VHE gamma-ray binaries appear to be very rare, and part is due to observational bias. Most instruments operating at TeV are pointed and must allocate time to observing many kinds of objects. The High Altitude Water Cherenkov (HAWC) Observatory, on the other hand, has high uptime (duty cycle >95%) and a wide field of view (2 sr), making it well-suited for observing transient and time-varying sources such as binaries. HAWC is also currently the only detector that is sensitive to gamma-ray photons above 10 TeV. Collected HAWC data spanning33 months between November 2014 and January 2018 are used to analyze the known and candidate VHE gamma-ray binary systems in this work. "Microquasars" are a special subclass of X-ray binaries that are also candidate VHE gamma-ray sources. Unlike other types of binaries, compact objects in microquasars accrete matter from their companion star. This process forms an accretion disk around the compact object and relativistic jets of particles are released perpendicular to the accretion disk. This feature is very similar to active galactic nuclei (AGN), only smaller in size. Given the fact that direct observation of particle acceleration in distant AGN is very challenging, microquasars grant the valuable opportunity to model similar processes using nearby objects in our own Galaxy. SS 433 is a known microquasar that has two jets ("east" and "west") terminating in radio lobes of a surrounding supernova remnant, W 50. The recent observation of SS 433 with HAWC marked the first direct evidence of gamma-ray emission from the jets of a microquasar. Using HAWC data, we have measured a VHE flux of [formula not rendered] at the jet interaction region e1 in the east lobe and [formula not rendered] in the west lobe with a combined post-trial statistical significance of 5:4. The systematic studies used to confirm the VHE gamma-ray emission at 20 TeV from the SS 433 jet interaction regions is discussed in this work, along with a brief description of the theoretical interpretation associated with the observation. The HAWC data were also used to search for gamma rays from the known VHE binaries HESS J0632+057 and LS 5039. No emission was observed from HESS J0632+057, so we compute upper limits on its flux. Emission at low statistical significance is observed from LS 5039, which is located in a crowded region of the Galactic plane and is contaminated by gamma rays from nearby extended sources. A multiple-source analysis of the region surrounding LS 5039, as well as a time-series analysis of the light curve from LS 5039, are presented. At this time, data from HAWC are not significant enough to support multi-TeV emission from LS 5039"--Pages xi-xiii.
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: Ruslan Konno Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Englische Version: Time-domain multi-messenger astronomy is the study of transient astrophysical phenomena using several messenger particles and waves. The High Energy Stereoscopic System (H.E.S.S.) is a ground-based telescope array, which measures very-high-energy gamma rays between 30 GeV and 100 TeV. Within this work, three H.E.S.S. transients follow-up programs and their results are shown. At first, the nova program is shown together with the detection of the 2021 RS Ophiuchi (RS Oph) outburst. RS Oph is a known nova with past eruptions. The analysis of the nova presented in this work shows a clear detection over the first five nights of observations, and a marginal detection two to four weeks after the eruption. RS Oph is thus the first Galactic transient phenomenon detected at ~1 TeV energies. A clear variability of the spectrum is shown. A discussion of the underlying physics concludes, that the observed gamma-ray emission most likely stems from cooled protons accelerated within an astrophysical shock. The results show time-resolved particle acceleration. The second program is the gravitational-waves (GWs) program. Here, the analysis of four observed binary black hole merger events is shown. No detection is reported, and upper limit sky maps are derived instead. The viability of GW follow-up with H.E.S.S. is discussed, and a case is made for a potential counterpart detection. The third program is the tidal disruption event (TDE) program, a pioneered program established at the emergence of the source class within the last few years. Unique challenges of the follow-up program are discussed, and the H.E.S.S. follow-up of the event AT2019uqv is shown. No detection is reported, and upper limits for AT2019uqv are given instead. [...].
Author: Ian Gabriel Wisher Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Blazars are some of the most energetic environments in the Universe with exceptionally strong non-thermal emission. Since the detection of VHE variability in the blazar Markarian 421, observations of blazars and their VHE variability have been an active field of research. Through long campaigns of observations, blazars have shown variability over timescales that vary from minutes to days across the electromagnetic spectrum from radio to TeV gamma rays. Though rare, the variability can also have extreme outburst events where the flux peaks at several orders of magnitude higher than the quiescent state of the source. These outbursts are interesting not only for constraining the models of acceleration and variability but also as tools to study other physics topics such as the extragalactic background light, intergalactic magnetic field, and Lorentz invariance. Though powerful, the rarity of these events makes studies challenging and motivates additional searches and detections. The High Altitude Water Cherenkov (HAWC) detector is an extensive air shower instrument with a high duty cycle, large field of view, and extraordinary sensitivity to TeV gamma rays. This allows HAWC to perform unbiased monitoring of a large number of different sources for flaring states and catch rare events such as the aforementioned blazar flares. This work presents a search for short timescale flares from known blazars and TeV sources for the first year of HAWC data with the capability to generate alerts in real time. In the course of this work, a variety of new hardware, software, and detection techniques were developed in conjunction with the construction of the HAWC detector. These include hardware development on the design of the main data acquisition system, electronics integrations and testing, design/testing of the online reconstruction system, and design of the electronics for the outrigger extension. Algorithms and methods to detect transients in HAWC time series data were developed and characterized to allow the rapid reporting of detected flares to other observatories for follow up observations. We identify several candidate flares from historical data that would have been good candidates for alerting other experiments. This shows the method is behaving as expected and capable of detecting and alerting other experiments of large flares.
Author: Publisher: ISBN: Category : Languages : en Pages : 187
Book Description
Blazars are some of the most energetic environments in the Universe with exceptionally strong non-thermal emission. Since the detection of VHE variability in the blazar Markarian 421, observations of blazars and their VHE variability have been an active field of research. Through long campaigns of observations, blazars have shown variability over timescales that vary from minutes to days across the electromagnetic spectrum from radio to TeV gamma rays. Though rare, the variability can also have extreme outburst events where the flux peaks at several orders of magnitude higher than the quiescent state of the source. These outbursts are interesting not only for constraining the models of acceleration and variability but also as tools to study other physics topics such as the extragalactic background light, intergalactic magnetic field, and Lorentz invariance. Though powerful, the rarity of these events makes studies challenging and motivates additional searches and detections. The High Altitude Water Cherenkov (HAWC) detector is an extensive air shower instrument with a high duty cycle, large field of view, and extraordinary sensitivity to TeV gamma rays. This allows HAWC to perform unbiased monitoring of a large number of different sources for flaring states and catch rare events such as the aforementioned blazar flares. This work presents a search for short timescale flares from known blazars and TeV sources for the first year of HAWC data with the capability to generate alerts in real time. In the course of this work, a variety of new hardware, software, and detection techniques were developed in conjunction with the construction of the HAWC detector. These include hardware development on the design of the main data acquisition system, electronics integrations and testing, design/testing of the online reconstruction system, and design of the electronics for the outrigger extension. Algorithms and methods to detect transients in HAWC time series data were developed and characterized to allow the rapid reporting of detected flares to other observatories for follow up observations. We identify several candidate flares from historical data that would have been good candidates for alerting other experiments. This shows the method is behaving as expected and capable of detecting and alerting other experiments of large flares.
Author: Alison Peisker
Author: Alison Peisker
Author: Kathryne Woodle
Author: Chang Dong Rho
Author: Matthew Rosenberg
Author: Ruslan Konno
Author: Ian Gabriel Wisher
Author: 
Author: Christian Skole
Author: Cosimo Bambi
Author: Miguel F Morales