Thesis (Ph. D.)--University of Chicago, Dept. of Physics, August 2000. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 155-158).

Astrophysical events that evolve on short timescales (from milliseconds to years) are widely referred as transient events. In many cases, transient events are explosions or mergers of astrophysical objects that emit particles of all energies. This thesis focuses on very-high-energy (VHE; 100 GeV to 100 TeV) gamma rays, observed by the VERITAS telescope, to understand two types of transients, superluminous supernovae (SLSNe) and classical novae. In the first part, the background physics and technical approach of an imaging atmospheric Cherenkov technique deployed by VERITAS is reviewed in depth, including the analysis pipeline of VERITAS data, from camera data reduction to high level analysis output. In addition to supporting the ongoing work at VERITAS, the second part of this thesis describes the extensive effort to develop, commission and align the optical system of the prototype Schwarzschild-Couder telescope, also located at the VERITAS observatory. This new telescope provides an wider field of view and higher angular resolution compared with the conventional IACT design of current telescopes, and will join the next generation of VHE telescopes in the Cherenkov Telescope Array (CTA) project currently in development. The observation and analysis of two SLSNe is performed, on SN 2015bn and SN 2017egm, with both VERITAS and Fermi-LAT telescopes. The upper limit is reported on both events and is compared to a simple and a self-consistent model for parameter estimation. In addition, a population of sources were analyzed to estimate the future detection potential of new SLSNe with several gamma-ray observatories. Finally, the observation and analysis of several novae were performed. These sources were observed with VERITAS and Fermi-LAT. The observation of Nova Herculis 2021 is noteworthy in that the overlap of both observations may constrain the cutoff energy of the nova spectral model, providing a estimate for the maximum energy of the accelerated particles in the nova’s shock region.

This project is to search for Very High Energy (VHE) (10¹¹ eV to 10¹⁴ eV) gamma rays from the Crab nebula and pulsar using the atmospheric Cherenkov imaging technique. The technique uses an array of 37 photomultiplier tubes to record the images of the Cherenkov light pulses generated by energetic particles in the air showers initiated by VHE gamma rays or charged cosmic rays. Gamma-ray-like events are selected from numerous cosmic-ray events based on the predicted properties of the image, such as the size, shape, and orientation with respect to the axis of the detector. A steady weak flux of VHE gamma rays from the Crab is detected at high statistical significance (9 sigma), which is not usually achieved in VHE gamma-ray astronomy. No strong evidence of pulsed emission is found when the same data is folded at the Crab pulsar's radio ephemeris. The angular resolution of the technique cannot separate the emission coming from the nebula from that from the pulsar. Although it is generally believed that the unpulsed emission is coming from the nebula, there may be an unpulsed component coming at only a couple of light cylinder radii away from the pulsar too. Using the outer gap model of pulsar, the spectrum is derived and is found to be compatible with the observations.

In this thesis, we explore and improve on the science of gamma-ray bursts with particular attention to the very-high-energy regime. We begin by discussing Imaging Atmospheric Cherenkov Telescope Arrays (IACTs), which are the primary instruments of observation at very-high-energy gamma rays. We focus on a particular, state-of-the-art IACT array in southern Arizona: Very Energetic Radiation Imaging Telescope Array System (VERITAS). We then discuss the science of gamma-ray bursts and what can be learned from IACT observations. We follow with a couple of technical improvements, allowing one to better search for and characterize gamma-ray bursts with IACTs. The techniques focus on statistical methods for detection of transient sources, as well as angular reconstruction at arbitrary zenith angles of observation. We then use one of our new statistical methods to search for a signal in VERITAS observations of gamma-ray burst locations, with tests designed to search for particular bursts as well as for hints of emission in the entire sample of observations. We conclude that there is no evidence for a signal and follow with a discussion of the particularly interesting non-detection of GRB 150323A. We discuss the implications of this non-detection on the energetics and ambient environment of this burst. We conclude that the VERITAS observations might indicate gamma-ray bursts taking place in the dense wind of Wolf-Rayet stars.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, June 1997. / Includes bibliographical references. Also available on the Internet.

Includes bibliographical references. / ix, 159 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1995

Bibliography: leaves 187-200 / x, 200 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1990

Thesis (Ph. D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1990. / Includes bibliographical references (leaves 187-200).

Thesis (Ph.D.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2008/02/12). Includes bibliographical references.