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Full-Text Articles in Physical Sciences and Mathematics
Unraveling The Physics Of Quasar Jets Using Hst Polarimetry, Devon Clautice
Unraveling The Physics Of Quasar Jets Using Hst Polarimetry, Devon Clautice
Theses and Dissertations
We present a multiwavelength study of three high-power FR II (quasar) jets -- 3C 273, PKS 0637-752, and 1150+497 -- with an emphasis on new high-quality Hubble Space Telescope (HST) optical polarimetry and Chandra X-ray Observatory imaging. Relativistic jets from active galactic nuclei transport energy and mass from the supermassive black hole’s accretion region out to Megaparsec-scale lobes, with effects that feedback into galaxy formation and cluster energetics. We build on recent work which has called into question our fundamental understanding of FR II jet physics, and suggest that highly-efficient particle acceleration must be taking place in situ …
A Comparison Of Automated Bolide Detection Methods, Maxine Thembi Khumalo
A Comparison Of Automated Bolide Detection Methods, Maxine Thembi Khumalo
Theses and Dissertations
Bolide recording and analysis are crucial so meteoroid fragments can be found, a lightcurve analyzed, and its trajectory calculated. The Spalding Allsky Camera Network (SACN) generates videos and composite images of the night sky that are potential meteors based on changes in brightness. The best way to ensure quick identification is to automate the detection of bolides (and all meteors) using computational techniques. This project tested three algorithms to sort events between those with and without meteors - a Traditional Hough Detection Method, Convolutional Neural Network (CNN), and YOLOv5 against the previous technique from 2018 by Elena Botella. All the …
Investigating The O’Connell Effect In Kepler Eclipsing Binaries, Matthew Frederick Knote
Investigating The O’Connell Effect In Kepler Eclipsing Binaries, Matthew Frederick Knote
Theses and Dissertations
The O’Connell effect – the presence of unequal maxima in eclipsing binaries – remains an unsolved riddle in the study of close binary systems. The Kepler space telescope produced high precision photometry of nearly 3,000 eclipsing binary systems, providing a unique opportunity to study the O’Connell effect in a large sample and in greater detail than in previous studies. I have characterized the observational properties – including temperature, luminosity, and eclipse depth – of a set of 212 systems (7.3% of Kepler eclipsing binaries) that display a maxima flux difference of at least 1%, representing the largest sample of O’Connell …
Infrared Search For N-Butane And Trans-2-Butene In Titan’S Atmosphere, Brendan Steffens
Infrared Search For N-Butane And Trans-2-Butene In Titan’S Atmosphere, Brendan Steffens
Theses and Dissertations
This dissertation constitutes a study of the possible presence of trace hydrocarbons, namely n-butane (n-C4H10) and trans-2-butene (trans-2-C4H8) in Titan’s atmosphere. These molecules, both of which bear specific connections of interest to Titan’s astrobiological potential, are predicted by photochemical models to occur at detectable abundances within Titan’s atmosphere. In spite of this, neither has been detected to date, by any means. For this work, both of these molecules were characterized in the laboratory by obtaining a comprehensive set of highresolution, infrared cross section measurements at cold temperatures appropriate for Titan. In the case of n-butane, a pseudoline list (i.e. an …
The Development Of A New All-In-One Allsky Camera And Radiometer System, Ashley Suzanne Hughes
The Development Of A New All-In-One Allsky Camera And Radiometer System, Ashley Suzanne Hughes
Theses and Dissertations
We developed a new all-in-one camera and radiometer system for meteor surveillance. It proved successful during its first bolide event on 13 April 2021, as reported in the journal Meteoritics and Planetary Science, volume 57, number 3, pages 575-587. The event capture produced both video and radiometric data, and with the video data we were able to calculate a trajectory and orbit, and determine the fragmentation characteristics of the meteor as it traveled through the atmosphere.
Extreme-Contrast Ratio Imaging Of Bright Star Fields Using Charge-Injection Devices, Sailee Mangesh Sawant
Extreme-Contrast Ratio Imaging Of Bright Star Fields Using Charge-Injection Devices, Sailee Mangesh Sawant
Theses and Dissertations
The intrinsic nature of many astronomical sources, such as exoplanets, binary and multiple star systems, circumstellar disks, and active galactic nuclei and their host galaxies, introduces challenging requirements for observational instrumentation and techniques. In each case, we encounter situations where the light from bright sources hampers our abilities to detect surrounding fainter targets. To explore and study all features of such extreme-contrast ratio (ECR) scenes, we must perform observations at the maximum possible contrast ratios. However, direct imaging of fainter objects in the vicinity of bright sources imposes limitations on the type of contrast ratios achievable using ground- and spacebased …
Intermittency Scaling Laws In Magnetohydrodynamic Turbulence: Theory, Simulations And Observations, Juan Carlos Palacios Caicedo
Intermittency Scaling Laws In Magnetohydrodynamic Turbulence: Theory, Simulations And Observations, Juan Carlos Palacios Caicedo
Theses and Dissertations
The main objective of this dissertation is to investigate intermittency of Magnetohydrodynamic (MHD) plasmas by means of high-resolution numerical simulations and large sets of solar wind data. Understanding intermittency scaling laws is a significant step forward towards understanding the fundamental properties of plasma turbulence and how spatial structures influence dissipation, heating, transport and acceleration of charged particles, which is important in a wide range of laboratory, space and astrophysical plasmas. The current stateof- the art in the theoretical understanding of intermittency in MHD turbulence is based on phenomenological (non-exact) models, numerical simulations and solar wind observations of structure functions of …
Arion 33: A Prospective Mission To Near-Earth Asteroids, Alita Regi
Arion 33: A Prospective Mission To Near-Earth Asteroids, Alita Regi
Theses and Dissertations
Near-Earth asteroids will become primary targets for space industrialization in the future as humanity becomes a multi-planetary species. But before such missions, it is necessary to survey these asteroids for their intrinsic scientific value. Exploring asteroids via orbiter missions can help us understand the asteroid's surface composition while providing us a cost and power model required for future missions. Therefore, it is beneficial to study asteroids to pave the way for future mining operations or more comprehensive scientific explorations. Hence, in this thesis, the target asteroids 2011 UW158 and 65803 Didymos are selected as case studies for the hypothetical mission …
A Numerical Study Of Jovian Moist Convection With A New Convective Adjustment Scheme, And Implications For Jupiter’S Water Abundance, Ramanakumar Sankar
A Numerical Study Of Jovian Moist Convection With A New Convective Adjustment Scheme, And Implications For Jupiter’S Water Abundance, Ramanakumar Sankar
Theses and Dissertations
Jupiter’s atmosphere features a variety of clouds that are formed from the interplay of chemistry and atmospheric dynamics, from the deep red of the Great Red Spot to the high altitude white ammonia clouds present in the zones. Beneath these upper level clouds, water condensation occurs, and sporadically leads to the formation of towering convective storms, driven by the release of large amounts of latent heat. These storms result in a widespread disruption of the cloud and dynamical structure of the atmosphere at the latitude where they form, making the study of these events paramount in understanding the dynamics at …
Timing Properties Of Active Galactic Nuclei, Evan Arnold Smith
Timing Properties Of Active Galactic Nuclei, Evan Arnold Smith
Theses and Dissertations
Timing properties of Active Galactic Nuclei (AGN) are investigated primarily using archival data from the Rossi X-ray Timing Explorer (RXTE) satellite collected between 1996 and 2011. The main emphasis is to search for quasi-periodic oscillations (QPOs). This search was motivated by the uniqueness of the RXTE AGN database, which contains a gold-mine of information on the long-term light curves of AGN, as well as the fact that QPOs are a common feature in the light curves of stellar mass black hole (BH) and neutron star (NS) X-ray Binaries (XRBs).In stellar mass systems, QPOs have been used as strong diagnostics about …
A Compositional Analysis Of Artificial And Terrestrial Analog Martian Regolith Simulants, Beverly Watson Kemmerer
A Compositional Analysis Of Artificial And Terrestrial Analog Martian Regolith Simulants, Beverly Watson Kemmerer
Theses and Dissertations
Over the past 50 years, significant advances in the knowledge of the topography, climate, and geology of Mars have taken place. The global Martian regolith composition is highly basaltic, primarily composed of pyroxene, plagioclase, and olivine, a mixture of Fe oxides and Fe-Ti oxides, and some alteration minerals, i.e. sulfates, carbonates, and clays. The particle size distribution of Martian regolith ranges from 1 µm to 1000 µm, with average Martian soil grain sizes being 250 µm to 300 µm. These regolith properties, as well as geotechnical properties, all play a part in the outcome of certain in situ resource utilization …
Deep Space Radiation Shelter Through Magnetic Shielding, Lauren Elizabeth Eastberg Persons
Deep Space Radiation Shelter Through Magnetic Shielding, Lauren Elizabeth Eastberg Persons
Theses and Dissertations
As human space exploration begins to reach beyond Earth for the first time in 50 years, we must prepare for the eventuality of long-duration missions outside the protection of Earth's magnetic field. In interplanetary space astronauts are exposed to highly energetic galactic cosmic radiation, most commonly in the range of 1-GeV protons. Present day shielding technologies are not sufficient to protect astronauts against such particles; as such, the following paper proposes an alternate method of creating deep space radiation shelters through the use of magnetic shielding. Using a series of circular superconducting loops arranged in the shape of a shell, …
Advanced Astroinformatics For Variable Star Classification, Kyle Burton Johnston
Advanced Astroinformatics For Variable Star Classification, Kyle Burton Johnston
Theses and Dissertations
This project outlines the complete development of a variable star classification algorithm methodology. With the advent of Big-Data in astronomy, professional astronomers are left with the problem of how to manage large amounts of data, and how this deluge of information can be studied in order to improve our understanding of the universe. While our focus will be on the development of machine learning methodologies for the identification of variable star type based on light curve data and associated information, one of the goals of this work is the acknowledgment that the development of a true machine learning methodology must …
X-Rays From Magnetic B-Type Stars, Corinne Fletcher
X-Rays From Magnetic B-Type Stars, Corinne Fletcher
Theses and Dissertations
Recent surveys have found that ∼10% of massive stars host strong, mostly dipolar magnetic fields with strengths on the order of a kilogauss. The prominent idea describing the interaction between the stellar winds and the magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the ionized wind material is forced to move along the closed magnetic field loops and collides at the magnetic equator, creating a shock (Δv ∼ 500−800 km s−1). As the shocked material cools radiatively, it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and probing the wind material …
Automated Software For The Detection Of Bolide Events, Elena Botella
Automated Software For The Detection Of Bolide Events, Elena Botella
Theses and Dissertations
The proper detection and analysis of bolide events ensures that we will once day be prepared for a big, catastrophic impact by a meteor. The data obtained from the analysis of these detected smaller events will provide important information about the meteor’s journey through our atmosphere and its orbit before it crossed the Earth’s path. SkySentinel is one of the All-Sky networks in charge of looking at the skies every night and detecting these objects as they fall. At the moment, SkySentinel’s detection process relies heavily on manpower to check whether their cameras picked up actual bolide events or false …
Testing The Wind-Shock Paradigm For B-Type Star X-Ray Production With Θ Carinae, Trisha F. Doyle
Testing The Wind-Shock Paradigm For B-Type Star X-Ray Production With Θ Carinae, Trisha F. Doyle
Theses and Dissertations
We present Chandra X-ray grating spectroscopy of the B0.2V star, θ Carinae. θ Car is in a critical transition region between the latest O-type and earliest B-type stars, where some of these stars are observed to have UV-determined mass-loss rates much lower than theoretically expected. In general, X-ray emission in this low-luminosity regime should be less prominent than in O-star winds, but observations have shown a higher than expected production of X-ray emission from the winds of these stars (e.g., Cohen et al. 2008; Huenemoerder et al. 2012). A hot wind could explain weak UV wind signatures, but this severely …
The Effects Of Thunderstorm Static And Quasi-Static Electric Fields On The Lower Ionosphere, Mohammad Ahmad Salem
The Effects Of Thunderstorm Static And Quasi-Static Electric Fields On The Lower Ionosphere, Mohammad Ahmad Salem
Theses and Dissertations
Thunderstorms and their lightning discharges are of great interest to many areas of geophysics and atmospheric electricity. A thunderstorm is an electric generator; it can produce both electrostatic and quasi-electrostatic fields in the overhead atmospheric D region. The D region is the lower part of the ionosphere that extends from about 40-90 km altitude where the electrons and ions are sufficient enough to affect the propagation of radio waves. In contrast to the electrostatic field, the quasi-electrostatic fields can be much stronger in magnitude, but shorter in duration, and can trigger halos. A halo is one type of the transient …
Geological Conditions Required For The Fluvial Erosion Of Titan’S Impact Craters, Rebeca M. Kinser
Geological Conditions Required For The Fluvial Erosion Of Titan’S Impact Craters, Rebeca M. Kinser
Theses and Dissertations
In comparison to other icy satellites, Titan has a small number of impact craters on its surface. Its dense atmosphere screens smaller impactors from the surface, but this alone does not account for the lack of impact craters, especially at large diameters. This suggests that Titan has a relatively young surface and/or erosional processes have effectively removed craters from its surface. For example, fluvial erosion could degrade craters such that they would be unrecognizable from an orbiting spacecraft such as Cassini. The amount of erosion, however, will depend on a number of factors including the geological and meteorological conditions of …
Reverberation Mapping Of The Dusty Torus In Active Galactic Nuclei, Erich Franz Geisert
Reverberation Mapping Of The Dusty Torus In Active Galactic Nuclei, Erich Franz Geisert
Theses and Dissertations
The Dusty Torus is a structure that is believed to exist in Active Galactic Nuclei. The Torus is physically too small to be spatially resolved, so Reverberation Mapping can be performed in order to replace spatial resolution with temporal resolution, yielding observations that can unravel the mystery of the Dusty Torus. One of the unknowns about the Torus is how the dust is distributed. The two competing theories are that either the dust resides in discrete clouds or that there is a solid wall of dust. This thesis presents the results of a year long observation program, starting in August …
Analysis Of Angular Momentum In Planetary Systems And Host Stars, Stacy Ann Irwin
Analysis Of Angular Momentum In Planetary Systems And Host Stars, Stacy Ann Irwin
Theses and Dissertations
The spin angular momentum of single Main Sequence stars has long been shown to follow a primary power law of stellar mass, J ∝ Mα, excluding stars of <2 solar masses. Lower mass stars rotate more slowly with and have smaller moments of inertia, and as a result they contain much less spin angular momentum. A secondary power law describes the upper bound of angular momenta of these less massive stars with a steeper slope. The Solar System’s orbital angular momentum, however, is of the same order of magnitude as the primary law, whereas the Sun’s spin angular momentum is consistent with the secondary relationship. This suggests that planets are an important clue to answering questions about stellar angular momentum loss and transfer. With recent advances in exoplanet discovery and characterization, the angular momenta of exoplanetary systems can now be determined. A method is developed to calculate planetary system angular momenta from the spin and orbital angular momenta of a sample including 426 host stars and 532 planets. To maximize the size of the working sample, systems discovered by both the transit and radial velocity methods are included, and the biases of both techniques are identified. Self-consistent stellar moment of inertia parameters are interpolated from grids of stellar evolutionary models. Main Sequence host stars range from 0.6 to 1.7 solar masses, and their angular momenta are shown to agree well with previous studies of stellar angular momentum, generally falling on or below the appropriate power law, and exhibiting detection method biases. The systems’ angular momenta, including both the planetary orbital and stellar spin components, are widely spread above and below the primary power law, but on average agree well with the primary relationship. The results indicate that the primary power law describes angular momenta of stars of <2 solar masses well, when planetary angular momentum is included. This relationship also holds across host star evolutionary classifications. For 90% of the systems, the angular momentum contained in the planets is greater than the spin angular momentum of the host star, a characteristic shared by the Solar System. Undetected planets contribute significant bias to the system angular momentum as well as to the proportion of angular momentum contained in the planets. This bias is used to identify systems which are likely to harbor additional planets in already known planetary systems, assuming the Solar System’s proportions are typical.
A Search For Planets And Brown Dwarfs Around Post Main Sequence Stars, Tomomi Otani
A Search For Planets And Brown Dwarfs Around Post Main Sequence Stars, Tomomi Otani
Theses and Dissertations
So far, the most promising theory for the existence of subdwarf B (sdB) stars is that they were formed during binary star evolution. This research was conducted to test this theory by searching for companions around six sdB pulsators (V391 Peg, HS 0702+6043, EC 20117-4014, PG 1219+534, PG 0911+456, and PG 1613+426) using the Observed-minus-Calculated (O-C) method. A star’s position in space will wobble due to the gravitational forces of any companion. If the star is emitting a periodic signal, the orbital motion of the star around the system’s center of mass causes periodic changes in the light pulse arrival …
Characterization Of Cataclysmic Variables And White Dwarfs In The Kepler Field, Trisha Doyle
Characterization Of Cataclysmic Variables And White Dwarfs In The Kepler Field, Trisha Doyle
Theses and Dissertations
We present long baseline Kepler photometry and ground-based Hale 20000 spectroscopy of five known white dwarfs, five newly identified white dwarfs, and a cataclysmic variable, V523 Lyr. Analysis of the photometric and spectroscopic data is used to characterize the white dwarfs and the cataclysmic variable, by determining preliminary fundamental parameters. We model the white dwarfs to determine their fundamental parameters, e↵ective temperature and surface gravity. If the e↵ective temperature of a white dwarf falls within a specific range, the white dwarf is expected to be a pulsator. We verified possible pulsation with complementary Kepler light curves when possible. The modeled …
A Statistical Analysis Of Wide Binary Evolution, Kyle Burton Johnston
A Statistical Analysis Of Wide Binary Evolution, Kyle Burton Johnston
Theses and Dissertations
Post main sequence (MS) mass loss causes orbital separation amplification in fragile (i.e. common proper motion) binary star systems. Components typically have separations around -1000 a.u. Such wide pairs experience negligible tidal interactions and mass transfer between companions; they evolve as two separate but coeval stars. In this paper we will attempt to model how post-MS mass loss statistically distorts a frequency distribution of fragile binary separations. Understanding this process provides a robust test of current theories of stellar evolution and sets constraints on the dynamics of the Galactic disk.