Astrophysics and Astronomy Commons^™

The A²Π–X²Σ⁺ Band System Of Yo, Peter F. Bernath, Manish Bhusal, Adam Pastorek

Chemistry & Biochemistry Faculty Publications

YO bands are conspicuous in the spectra of S stars. The laboratory spectrum of the A²Π–X²Σ⁺ electronic transition has been recorded with a Fourier transform spectrometer using a composite-wall hollow cathode lamp source. The A²Π–X²Σ⁺ transition with v ' ≤ 4 and v'' ≤ 4 has been rotationally analyzed using the modern spectral fitting program PGOPHER. Vibronic band strengths were calculated using an ab initio transition dipole moment function. A line list for the A²Π–X²Σ⁺ transition is provided and can be utilized in the modeling …

Visible Opacities Of S-Type Stars: The D³Φ–A³Δ Band System Of Zro, Peter F. Bernath, Manish Bhusal, Jacques Liévin

Chemistry & Biochemistry Faculty Publications

ZrO is a well-studied metal monoxide because of its astrophysical importance in characterizing S stars. The bands of the d³Φ–a³Δ system (γ system) with v′≤4 and v" ≤ 5 are rotationally analyzed using the PGOPHER program to provide spectroscopic constants. The high-resolution ZrO emission spectrum was recorded with a Fourier transform spectrometer using a high-temperature carbon furnace source. New ab initio calculations of the transition dipole moment were carried out in order to determine the vibronic band strengths. The spectroscopic constants, along with the band strengths, are used to calculate a line list for the γ system. This line list …

Opacities Of S-Type Stars: The Singlet B¹⊓−X¹Σ⁺, B¹⊓−A¹Δ, And C¹Σ⁺−X¹Σ⁺ Band Systems Of Zro, Peter F. Bernath, Manish Bhusal, Jacques Liévin

Chemistry & Biochemistry Faculty Publications

The ZrO B¹Π–X¹Σ⁺, B¹Π–A¹Δ, and C¹Σ+–X¹Σ⁺ band systems are important opacity sources in the near-infrared and optical spectra of S-type stars. A total of 21 rovibronic bands with v'' ≤ 7 and v' ⩽ 5 were observed and fit for the B¹Π–X¹Σ⁺ transition, five bands for the ⁹⁰ZrO B¹Π–A¹Δ transition and one band for the ⁹⁰ZrO C¹Σ⁺–X¹Σ⁺ transition. All band …

Conventions, Definitions, Identities, And Other Useful Formulae, Robert A. Mcnees Iv

Physics: Faculty Publications and Other Works

As the name suggests, these notes contain a summary of important conventions, definitions, identities, and various formulas that I often refer to. They may prove useful for researchers working in General Relativity, Supergravity, String Theory, Cosmology, and related areas.

Exploring The Hot And Gaseous Universe From Infrared To X-Ray, Chamani Gunasekera

Theses and Dissertations--Physics and Astronomy

Over 90% of baryonic matter in the universe exists as astrophysical plasmas. The gas
is often far from thermodynamic equilibrium, so numerical non-equilibrium spectral
synthesis simulations are used to understand observations. cloudy simulates vari-
ous physical conditions, providing spectra predictions. This thesis aims to meet the
challenge of new observatories like the JWST (James Webb Space Telescope) and
XRISM (X-Ray Imaging Spectroscopy Mission). These simulations are no better
than the underlying atomic and molecular database and the fourth chapter details
a long-needed update to an evolving database. The predicted spectra are strongly
affected by the composition of the gas, which …

Spinning Spheroidal Components Of Disk Galaxies: Resonant Interactions With Stellar Bars, Xingchen Li

Theses and Dissertations--Physics and Astronomy

The majority of disk galaxies possess stellar bars, which are the main driver in the internal evolution of barred galaxies. Bars represent non-axisymmetric perturbations in the galactic disks, producing strong gravitational torques that facilitate angular momentum transfer from the disk to the spheroidal components, such as central stellar bulges and host dark matter (DM) halos. The redistribution of angular momentum in barred galaxies proceeds mainly via resonant interactions between the bar and orbits in the spheroids. The amount of angular momentum emitted or absorbed at each resonance depends on the mass distribution, density and spin in the spheroidal components. Thus, …

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 …

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 …

The Effects Of Environmental Factors On Tsunami Propagation And Inundation: A Comparison Of Earth With Other Planetary Bodies, Austin Halstead

All Master's Theses

Tsunamis are a universal hazard in any environment with oceans or lakes. Having a firm understanding of them is essential because of this. However, the vast number of tsunami studies have been solely on Earth, despite the growing evidence of oceans and lakes being on, or having once existed on, other planets and moons. In this study, I investigated tsunami behavior in non-Earth environments by testing the effects of varying viscosity and gravity. I conducted simulations using GeoClaw, Flow3D®, and VolcFlow on established tsunami benchmarks to identify consistent patterns in tsunami flow patterns and inundation. The results show …

Ultradeep Atca Imaging Of 47 Tucanae Reveals A Central Compact Radio Source, Alessandro Paduano, Arash Bahramian, James C. A. Miller-Jones, Adela Kawka, Tim J. Galvin, Liliana E. Rivera Sandoval, Sebastian Kamann, Jay Strader, Laura Chomiuk, Craig O. Heinke

Physics & Astronomy Faculty Publications

We present the results of an ultradeep radio continuum survey, containing ∼480 hr of observations, of the Galactic globular cluster 47 Tucanae with the Australia Telescope Compact Array. This comprehensive coverage of the cluster allows us to reach rms noise levels of 1.19 μJy beam−1 at 5.5 GHz, 940 nJy beam−1 at 9 GHz, and 790 nJy beam−1 in a stacked 7.25 GHz image. This is the deepest radio image of a globular cluster and the deepest image ever made with the Australia Telescope Compact Array. We identify ATCA J002405.702-720452.361, a faint (6.3 ± 1.2 μJy at 5.5 …

Hubble Tension And Gravitational Self-Interaction, Corey Sargent, William Clark, Alexander Deur, Balša Terzić

Physics Faculty Publications

One of the most important problems vexing the ΛCDM cosmological model is the Hubble tension. It arises from the fact that measurements of the present value of the Hubble parameter performed with low-redshift quantities, e.g. the Type IA supernova, tend to yield larger values than measurements from quantities originating at high-redshift, e.g. fits of cosmic microwave background radiation. It is becoming likely that the discrepancy, currently standing at 5σ, is not due to systematic errors in the measurements. Here we explore whether the self-interaction of gravitational fields in General Relativity, which are traditionally neglected when studying the evolution …

Fully Relativistic Derivation Of The Thermal Sunyaev-Zel'dovich Effect, Balša Terzić, Geoffrey A. Krafft, William Clark, Alexandre Deur, Emerson Rogers, Ioannis Sakiotis, Brandon Velasco

Physics Faculty Publications

We present the first fully and inherently relativistic derivation of the thermal Sunyaev-Zel'dovich effect. This work uses the formalism historically applied to compute radiation spectra emerging from inverse Thomson/Compton sources of x-ray radiation. Comparing our results to the traditional approach based on relativistically-corrected classical Kompaneets equation, we find small, but systematic differences. Most notable are the modest (⩽10%) differences in the crossover frequency where the spectral distortion due to the Sunyaev-Zel'dovich effect vanishes, and the quadratic scaling of the energy shift with the electron cloud temperatures.

A Multi-Wavelength Determination Of The Total Luminosity And Star Formation Rate Of The Milky Way, Joshua L. Mascoop

Graduate Theses, Dissertations, and Problem Reports (ETD)

The star formation rate (SFR) of the Milky Way is poorly understood in comparison to the SFR of other galaxies. In order to better find the Galaxy's place in the universe, it is imperative to understand the star formation activity occurring within it. We characterize the Galactic \hii\ region luminosity function (LF) at multiple infrared and radio wavelengths using a sample of 797 first Galactic quadrant \hii regions compiled from the WISE Catalog of Galactic \hii Regions. This sample is statistically complete for all regions powered by single stars of type O9.5V and earlier.

We find that neither a single …

An Observational Census Of Post-Merger Galaxies And Supermassive Black Hole Pair Evolution, Gregory Walsh

Graduate Theses, Dissertations, and Problem Reports (ETD)

Massive galaxy mergers are a fundamental consequence of the dynamic evolution of the Universe and play a central role in the evolution of galaxies. Because all massive galaxies harbor a central supermassive black hole (SMBH; M ≥ 10⁶ M_⊙), studying these merging systems with electromagnetic (EM) techniques constrains galaxy evolution models and provides a systematic means to examine the astrophysical mechanisms that facilitate the growth of SMBHs. These growing SMBHs are observable across the EM spectrum as Active Galactic Nuclei (AGN). Massive galaxy mergers are a natural formation mechanism for an SMBH pair, eventually evolving into an …

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 …

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.