Astrophysics and Astronomy Commons^™

A Hyperbolic Relaxation Solver For Numerical Relativity, Thiago Assumpcao

Graduate Theses, Dissertations, and Problem Reports (ETD)

Numerical relativity (NR) simulations are essential for self-consistently modeling compact binary mergers, whose observations form the heart of gravitational-wave science. Stable NR simulations are the result of mathematical and computational breakthroughs spanning several decades: early attempts to numerically solve the two-body problem in General Relativity (GR) date back to the 1960s, while the first successful black-hole binary merger simulations were performed in 2005 with the generalized harmonic coordinates, and in 2006 using the moving-puncture gauge.

Today, NR continues to drive progress in gravity research, with ongoing efforts focused on increasing physical realism in simulations containing matter, exploring alternative theories of …

Analysis Of Pulsar Discoveries And Pulse Profile Variability: From Pulsar Candidates To Gravitational Wave Detector, William Carl Fiore

Graduate Theses, Dissertations, and Problem Reports (ETD)

Last year, pulsar timing arrays (PTAs) reported evidence of a gravitational-wave (GW) background at nanohertz frequencies, opening a new window into the Universe. PTAs measure GW-induced variations in the timing of radio pulses from millisecond pulsars (MSPs) in our Galaxy. In order for PTA experiments to confidently detect and characterize the GW background, they must continue to regularly observe many MSPs and measure their pulse times of arrival as precisely as possible. This motivates efforts to find new MSPs with pulsar surveys, and to study pulsars whose unusual behavior may give rise to excess noise in PTA data sets, potentially …

The Search, The Localization, And The Characterization: Fast Radio Transients, Reshma Anna Thomas

Graduate Theses, Dissertations, and Problem Reports (ETD)

Fast radio transients are energetic bursts in centimeter or meter wave-lengths, lasting only milliseconds, and originating from both Galactic and extra-Galactic sources. In our Galaxy, these transients primarily originate from pulsars, which are rotating neutron stars. The more energetic extra-galactic transients, known as fast radio bursts (FRBs), have unknown origins. This thesis explores various techniques, including single dish and interferometric observations, to detect and accurately localize fast radio transients. It also investigates how the propagation effects of radio waves can reveal characteristics of the local environment and potential FRB sources. Furthermore, it demonstrates how FRBs can be used to study …

Study Of Particle Accelerators In The Universe With The Hawc Observatory, Rishi Babu

Dissertations, Master's Theses and Master's Reports

HESS J1809-193 is an unidentified TeV source discovered in 2007 by the High Energy Stereoscopic System(H.E.S.S.) Collaboration. The emission originates in a region that is rich in cosmic-ray accelerators, including several supernova remnants and pulsars, including SNR G11.1+0.1, SNR G11.0-0.0, and the young radio pulsar PSR J1809-1917. Originally classified as a pulsar wind nebula candidate, recent studies show the peak of the TeV region overlapping with a system of molecular clouds and revising the original classification for other scenarios, including a pure hadronic scenario. This dissertation presents the morphological and spectral study of HESS J1809-193 using 2139 days of data …

Constructing The 4th Hawc Catalog Of Very-High-Energy Sources Using An Automated Likelihood Pipeline Search, Samuel J. Groetsch

Dissertations, Master's Theses and Master's Reports

In this thesis, I present an analysis pipeline that allows one to search for and identify sources of very-high-energy (VHE) γ-ray emission in sky maps created from data collected with the High Altitude Water-Cherenkov (HAWC) Observatory. The HAWC Observatory is located at about 4100 m elevation just below Pico de Orizaba, the highest mountain in Mexico also known as Citlaltepetl (from the Nahuatl words citlal(in) = star, and tepetl = mountain). The observatory is an array of several hundred detector stations that measure signals from particle showers, so-called extensive air showers (EAS), that are initiated in interactions of primary cosmic …

Young Atmospheres Spiriting Away, Keighley Elizabeth Rockcliffe

Dartmouth College Ph.D Dissertations

The astronomy community has spectacularly achieved the first step in characterizing exoplanets: discovery. Over three decades of exoplanet detection have populated the Milky Way's exoplanet mosaic with thousands of planets, and more are on the way. Key trends within this mosaic reveal atmospheric escape as an underlying evolutionary process that has significantly shaped the population. While we are aware that atmospheric escape plays some role in exoplanet evolution, we do not know the extent of its influence, how it compares to other processes, and its specific physical mechanisms. Detailed studies of individual systems at known, young ages are direct tests …

Studying The Impact Of The Geospace Environment On Solar Lithosphere Coupling And Earthquake Activity, Dimitar Ouzounov, Galina Khachikyan

Mathematics, Physics, and Computer Science Faculty Articles and Research

In solar–terrestrial physics, there is an open question: does a geomagnetic storm affect earthquakes? We expand research in this direction, analyzing the seismic situation after geomagnetic storms (GMs) accompanied by the precipitation of relativistic electrons from the outer radiation belt to form an additional radiation belt (RB) around lower geomagnetic lines. We consider four widely discussed cases in the literature for long-lived (weeks, months) RBs due to GMs and revealed that the 1/GMs 24 March 1991 with a new RB at L~2.6 was followed by an M7.0 earthquake in Alaska, 30 May 1991, near footprint L = 2.69; the 2/GMs …

A Closer Look At Our Ever-Changing Solar System, Erik Johnson

Natural Science Faculty

What is a planet? It's a question that was controversial when Pluto was reclassified in 2006. The definition has changed over time as people have learned more about the universe. There are still unresolved differences between the cultural usage and its various scientific uses.

Radio Insights Into Gamma-Ray Mysteries, Seth M. Bruzewski

Physics & Astronomy ETDs

In the time since its launch, the \textit{Fermi Gamma-Ray Space Telescope} has provided new and unparalleled views of the $\gamma$-ray sky, dramatically increasing our understanding of sources of high-energy radiation. During that same time, however, its ``unassociated'' sources have provided a consistent mystery: approximately one third of the modern gamma-ray sky remains completely unaccounted for in other electromagnetic regimes. While some of the fainter sources simply pose challenges in achieving the necessary signal-to-noise ratio, others are well constrained and have resisted traditional investigations for years, and in some cases, for over a decade. Radio astronomy has traditionally been the best …

Modeling Lithographic Quantum Dots And Donors For Quantum Computation And Simulation, Mitchell Ian Brickson

Physics & Astronomy ETDs

Our first focus is on few-hole quantum dots in germanium. We use discontinous Galerkin methods to discretize and solve the equations of a highly detailed k·p model that describes these systems, enabling a better understanding of experimental magnetospectroscopy results. We confirm the expected anisotropy of single-hole g-factors and describe mechanisms by which different orbital states have different g-factors. Building on this, we show that the g-factors in Ge holes are suciently sensitive to details of the device electrostatics that magnetospectroscopy data can be used to make a prediction of the underlying confinement potential. The second focus is on designing quantum …

Stability Of Metal Fluoride Films When Irradiated With Electron Beam, Devin M. Lewis, Waseem Ashraf

Student Works

LiF is an essential mirror coating for the upcoming LUVOIR space telescope. In order to improve the technology readiness level of this material a study was to be conducted, observing the surface changes of LiF thin films as exposed to humidity for extended periods of time. However, initial attempts to characterize the film with SEM showed that LiF is unstable under all electron beam parameters experimented with. This creates the concern that LiF is also sensitive to other forms of radiation damage. Further investigation may suggest the need to transition to another mirror coating that is more resilient to radiation …

Celestial Bodies, Rebecca L. Rand, Mark Popinchalk

Capstones

Most of us will never come close to touching space. But space touches us every day. On Celestial Bodies, journalist Rebecca Rand and astronomer Mark Popinchalk explore the ways outer space interacts with life on earth.

In Episode 1, hosts Rebecca Rand and Mark Popinchalk explore how, for millions of years, trees have been recording celestial events in space. Within the rings of their trunks, trees store radiation from solar flares, supernovae, and changes in the earth’s magnetic field. The hosts talk to Dr. Ben Pope to learn more about what we can discover by looking at radioactive molecules …

The High Energy X-Ray Probe (Hex-P): A New Window Into Neutron Star Accretion, R.M. Ludlam, C. Malacaria, E. Sokolova-Lapa, F. Fuerst, P. Pradhan, A.W. Shaw, K. Pottschmidt, S. Pike, G. Vasilopoulos, J. Wilms, J.A. Garcia, K. Madsen, D. Stern, C. Maitra, M. Del Santo, D.J. Walton, M.C. Brumback, J. Van Den Eijnden

Publications

Accreting neutron stars (NSs) represent a unique laboratory for probing the physics of accretion in the presence of strong magnetic fields (B ≳ 10⁸ G). Additionally, the matter inside the NS itself exists in an ultra-dense, cold state that cannot be reproduced in Earth-based laboratories. Hence, observational studies of these objects are a way to probe the most extreme physical regimes. Here we present an overview of the field and discuss the most important outstanding problems related to NS accretion. We show how these open questions regarding accreting NSs in both low-mass and high-mass X-ray binary systems can …

Separated Twins Or Just Siblings? A Multiplanet System Around An M Dwarf Including A Cool Sub-Neptune, M. Harris, D. Dragomir, I. Mireles, K. A. Collins, S. Ulmer-Moll, S. B. Howell, K. G. Stassun, G. Zhou, C. Ziegler, F. Bouchy, C. Briceño, D. Charbonneau, K. I. Collins, G. Fűűrész, N. M. Guerrero, J. M. Jenkins, Eric L.N. Jensen, M. H. K. Kristiansen, N. Law, M. Lendl, A. W. Mann, H. P. Osborn, S. N. Quinn, G. R. Ricker, R. P. Schwarz, S. Seager, E. B. Ting, R. Vanderspek, D. Watanabe, J. N. Winn

Physics & Astronomy Faculty Works

We report the discovery of two TESS sub-Neptunes orbiting the early M dwarf TOI-904 (TIC 261257684). Both exoplanets, TOI-904 b and c, were initially observed in TESS Sector 12 with twin sizes of 2.426 (+0.163)/(-0.157) and 2.167 (+0.130)/(-0.118) R_⊕, respectively. Through observations in five additional sectors in the TESS primary mission and the first and second extended missions, the orbital periods of the planets were measured to be 10.887 ± 0.001 and 83.999 ± 0.001 days, respectively. Reconnaissance radial velocity measurements (taken with EULER/CORALIE and SMARTS/CHIRON) and high-resolution speckle imaging with adaptive optics (obtained from SOAR/HRCAM and Gemini …

Jwst: Deuterated Pahs, Pah-Nitriles, And Pah 4 Overtone And Combination Bands I: Program Description And First Look, C. Boersma, L. J. Allamandola, Vincent J. Esposito, A. Maragkoudakis, J. D. Bregman, P. Temi, T. J. Lee, R. C. Fortenberry, E. Peeters

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

A first look is taken at the NIRSpec 1–5 μm observations from James Webb Space Telescope program 1591 that targets seven objects along the low-mass stellar life cycle with polycyclic aromatic hydrocarbon (PAH) emission. Spectra extracted from a 1'.'5 radius circular aperture are explored, showing a wealth of features, including the 3 μm PAH complex, the PAH continuum, and atomic and molecular emission lines from H i, He, H₂, and other species. CO₂- and H₂O-ice absorption and CO emission is also seen. Focusing on the bright-PDR position in M17, the PAH CH stretch falls …

Gwtc-3: Compact Binary Coalescences Observed By Ligo And Virgo During The Second Part Of The Third Observing Run, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, Teviet Creighton, Mario C. Diaz, F. Llamas, Soma Mukherjee, Volker Quetschke, Wenhui Wang

Physics & Astronomy Faculty Publications

The third Gravitational-Wave Transient Catalog (GWTC-3) describes signals detected with Advanced LIGO and Advanced Virgo up to the end of their third observing run. Updating the previous GWTC-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (O3b) between 1 November 2019, 15∶00 Coordinated Universal Time (UTC) and 27 March 2020, 17∶00 UTC. There are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin ��astro>0.5. Of these, 18 were previously reported as low-latency public alerts, and 17 are reported …

Gwtc-3: Compact Binary Coalescences Observed By Ligo And Virgo During The Second Part Of The Third Observing Run, R. Abbott, T. Abbott, F. Acernese, K. Ackley, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Wenhui Wang, Francisco Llamas

Physics & Astronomy Faculty Publications

The third Gravitational-Wave Transient Catalog (GWTC-3) describes signals detected with Advanced LIGO and Advanced Virgo up to the end of their third observing run. Updating the previous GWTC-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (O3b) between 1 November 2019, 15 ∶ 00 Coordinated Universal Time (UTC) and 27 March 2020, 17 ∶ 00 UTC. There are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin p astro > 0.5 . Of these, 18 were previously reported as low-latency …

Cooperative Observing At A Modest-Sized Observatory, Michael D. Joner, Denzil E. Watts Iv, Seneca H. Bahr, Oliver Hancock, Michael W. Holland, Hafsa Jamil, Eden Saxton, Malaya Williams-Jones

BYU West Mountain Observatory Project

The West Mountain Observatory is an astronomical research facility operated by Brigham Young University, located on an isolated mountain approximately 22 kilometers southwest of the main Provo UT campus. The observatory was upgraded 15 years ago and has since been utilized primarily as an undergraduate research facility. The observatory is well suited to do work on projects utilizing time series photometric observations and has been particularly successful at conducting multiple projects for undergraduate student researchers that require observations of different durations and cadences using various filter combinations. This requires additional planning and cooperation between the different programs that are often …

Uv-Optical Emission Of Ab Aur B Is Consistent With Scattered Stellar Light, Yifan Zhou, Brendan P. Bowler, Haifeng Yang, Aniket Sanghi, Gregory J. Herczeg, Adam L. Kraus, Jaehan Bae, Feng Long, Katherine B. Follette, Kimberly Ward-Duong, Zhaohuan Zhu, Lauren Biddle, Laird M. Close, Lillian Yushu Jiang, Ya Lin Wu

Astronomy: Faculty Publications

The proposed protoplanet AB Aur b is a spatially concentrated emission source imaged in the millimeter-wavelength disk gap of the Herbig Ae/Be star AB Aur. Its near-infrared spectrum and absence of strong polarized light have been interpreted as evidence supporting the protoplanet interpretation. However, the complex scattered-light structures in the AB Aur disk pose challenges in resolving the emission source and interpreting the true nature of AB Aur b. We present new images of the AB Aur system obtained using the Hubble Space Telescope Wide Field Camera 3 in the ultraviolet (UV) and optical bands. AB Aur b and the …

The Comprehensive Archive Of Substellar And Planetary Accretion Rates, S. K. Betti, K. B. Follette, K. Ward-Duong, A. E. Peck, Y. Aoyama, J. Bary, B. Dacus, S. Edwards, G. D. Marleau, K. Mohamed, J. Palmo, C. Plunkett, C. Robinson, H. Wang

Astronomy: Faculty Publications

Accretion rates ( M ̇ ) of young stars show a strong correlation with object mass (M); however, extension of the M ̇ - M relation into the substellar regime is less certain. Here, we present the Comprehensive Archive of Substellar and Planetary Accretion Rates (CASPAR), the largest compilation to date of substellar accretion diagnostics. CASPAR includes: 658 stars, 130 brown dwarfs, and 10 bound planetary mass companions. In this work, we investigate the contribution of methodological systematics to scatter in the M ̇ - M relation and compare brown dwarfs to stars. In our analysis, we rederive all quantities …

First Vlti/Gravity Observations Of Hip 65426 B: Evidence For A Low Or Moderate Orbital Eccentricity, Sarah Blunt, W. O. Balmer, J. J. Wang, S. Lacour, S. Petrus, G. Bourdarot, J. Kammerer, N. Pourré, E. Rickman, J. Shangguan, T. Winterhalder, R. Abuter, A. Amorim, R. Asensio-Torres, M. Benisty, J. P. Berger, H. Beust, A. Boccaletti, A. Bohn, M. Bonnefoy, H. Bonnet, W. Brandner, F. Cantalloube, P. Caselli, B. Charnay, G. Chauvin, A. Chavez, E. Choquet, V. Christiaens, Y. Clénet, Et Al, Kimberly Ward-Duong

Astronomy: Faculty Publications

Giant exoplanets have been directly imaged over orders of magnitude of orbital separations, prompting theoretical and observational investigations of their formation pathways. In this paper, we present new VLTI/GRAVITY astrometric data of HIP 65426 b, a cold, giant exoplanet which is a particular challenge for most formation theories at a projected separation of 92 au from its primary. Leveraging GRAVITY’s astrometric precision, we present an updated eccentricity posterior that disfavors large eccentricities. The eccentricity posterior is still prior dependent, and we extensively interpret and discuss the limits of the posterior constraints presented here. We also perform updated spectral comparisons with …

A Deeper Understanding Of The R Process, Mengke Li

All Dissertations

The overarching aim of my PhD research is to deepen our understanding of r-process nu- cleosynthesis. The initial phase of my work involved developing a Machine Learning-based nuclear mass model, specifically tailored to predict nuclear masses crucial for r-process nucleosynthesis. This model was then applied to simulate the r-process, focusing on neutron-rich nuclei significant to nucleosynthesis. The simulations yielded r-process abundance patterns, extending up to thorium and uranium, that align qualitatively with the observed solar system abundance patterns, with the characteristic peaks well positioned. Advancing our study further, we introduced a novel graph-based methodology named GrRproc for calculating r-process abundances. …

An Investigation Of The Accretion Processes In T Tauri And Herbig Ae/Be Systems Using High Resolution Optical And Near-Infrared Spectroscopy, Joshua Kern

All Dissertations

Star and planet formation is intimately tied to the accretion of material from the environments in which they form. During the formation process, disks of gas and dust develop in young stellar objects through which material is facilitated to the star and forming planets. Theoretical models of these accretion processes invoke viscous spreading via hydrodynamics, as well as more complex interactions with magnetic fields be it from the stellar component or the formation environment in order to catalyze these mass flows. These accretion models predict various scenarios including magnetospheric accretion as well as supersonic accretion flows in the disk atmosphere …

Godel, Escherian Staircase And Possibility Of Quantum Wormhole With Liquid Crystalline Phase Of Iced-Water - Part I: Theoretical Underpinning, Victor Christianto, T. Daniel Chandra, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

As a senior physicist colleague and our friend, Robert N. Boyd, wrote in a journal (JCFA, Vol. 1,. 2, 2022), Our universe is but one page in a large book [4]. For example, things and Beings can travel between Universes, intentionally or unintentionally. In this short remark, we revisit and offer short remark to Neil’s ideas and trying to connect them with geometrization of musical chords as presented by D. Tymoczko and others, then to Escher staircase and then to Jacob’s ladder which seems to point to possibility to interpret Jacob’s vision as described in the ancient book of Genesis …

Godel, Escherian Staircase And Possibility Of Quantum Wormhole With Liquid Crystalline Phase Of Iced-Water - Part Ii: Experiment Description, Victor Christianto, T. Daniel Chandra, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

The present article was partly inspired by G. Pollack’s book, and also Dadoloff, Saxena & Jensen (2010). As a senior physicist colleague and our friend, Robert N. Boyd, wrote in a journal (JCFA, Vol. 1, No. 2, 2022), for example, things and Beings can travel between Universes, intentionally or unintentionally [4]. In this short remark, we revisit and offer short remark to Neil Boyd’s ideas and trying to connect them with geometry of musical chords as presented by D. Tymoczko and others, then to Escherian staircase and then to Jacob’s ladder which seems to pointto possibility to interpret Jacob’s vision …

Cd-27°11535: Evidence For A Triple System In The Β Pictoris Moving Group, Andrew D. Thomas, Eric L. Nielsen, Robert J. De Rosa, Anne E. Peck, Bruce Macintosh, Jeffrey Chilcote, Paul Kalas, Jason J. Wang, Sarah Blunt, Alexandra Greenbaum, Quinn M. Konopacky, Michael J. Ireland, Peter Tuthill, Kimberly Ward-Duong, Lea A. Hirsch, Ian Czekala, Franck Marchis, Christian Marois, Max A. Millar-Blanchaer, William Roberson, Adam Smith, Hannah Gallamore, Jessica Klusmeyer

Astronomy: Faculty Publications

We present new spatially resolved astrometry and photometry of the CD -27°11535 system, a member of the β Pictoris moving group consisting of two resolved K-type stars on a ∼20 yr orbit. We fit an orbit to relative astrometry measured from NIRC2, GPI, and archival NaCo images, in addition to literature measurements. However, the total mass inferred from this orbit is significantly discrepant from that inferred from stellar evolutionary models using the luminosity of the two stars. We explore two hypotheses that could explain this discrepant mass sum: a discrepant parallax measurement from Gaia due to variability, and the presence …

Wallaby Pre-Pilot Survey: Ultra-Diffuse Galaxies In The Eridanus Supergroup, B.-Q. For, K. Spekkens, L. Staveley-Smith, K. Bekki, A. Karunakaran, B. Catinella, Bärbel S. Koribalski, K. Lee-Waddell, Juan P. Madrid, C. Murugeshan

Physics & Astronomy Faculty Publications

We present a pilot study of the atomic neutral hydrogen gas (H I) content of ultra-diffuse galaxy (UDG) candidates. In this paper, we use the pre-pilot Eridanus field data from the Widefield ASKAP L-band Legacy All-sky Blind Survey to search for H I in UDG candidates found in the Systematically Measuring Ultra-diffuse Galaxies survey (SMUDGes). We narrow down to 78 SMUDGes UDG candidates within the maximum radial extents of the Eridanus subgroups for this study. Most SMUDGes UDGs candidates in this study have effective radii smaller than 1.5 kpc and thus fail to meet the defining size threshold. We …

Temporal And Spectral Analysis Of 1es 2344+514 In Two Flaring States Observed By Veritas, Connor Poggemann

Physics

VERITAS observed the bright blazar 1ES 2344+514 during two flaring periods, one from Dec. 17 to Dec. 18, 2015 (MJD 57373-57374) with a peak flux of ~60% of the Crab and another from Nov. 28 to Dec. 3, 2021 (MJD 59546-59551) with a peak flux of ~20% of the Crab. This blazar, located at a redshift of z = 0.044, is classified as an extreme high-frequency-peaked BL Lacertae object (HBL). It is known to be variable, including several previous day-scale flares: Whipple on Dec. 20, 1995, VERITAS on Dec. 7, 2007, and MAGIC on Aug. 11, 2016. The VERITAS near-nightly …

Teaching Introductory Physics In The Context Of Personal And Societal Issues Of The Covid-19 Pandemic, Guang Zeng, Liang Zeng

Physics & Astronomy Faculty Publications

This paper reports on introductory physics instruction contextualized in terms of coronavirus-related personal and societal issues. Students in this descriptive qualitative study gained a strong grasp of a range of physics concepts associated with the nature and mechanisms of the spread of the coronavirus, such as projectile motion, air convection, Reynolds number, and Brownian motion; additionally, they were able to discuss the application of physics relevant to the N95 face masks. Students found this pedagogical approach engaging, as shown in their reflective writing.

Initiation Criteria For The Onset Of Geomagnetic Substorms Based On Auroral Observations And Electrojet Current Signatures, Mayowa Michael Kayode-Adeoye

Graduate Theses and Dissertations (2019 - present)

In recent years, several substorm onset criteria have been developed, either from auroral observations (many authors) or from auroral electrojet properties such as those described by (Forsyth et al., 2015; Maimaiti et al., 2019; Newell & Gjerloev, 2011; Partamies et al., 2011) The different criteria are being investigated using a low order physics model of the magnetosphere called WINDMI (Spencer et al., 2009) and inferences are being made in line with the WINDMI model. The model variables will be compared with the criteria for substorm onset proposed by examining the SML index.

The WINDMI model uses solar wind and IMF …