Astrophysics and Astronomy Commons^™

A Nustar Census Of The X-Ray Binary Population Of The M31 Disk, Hannah Moon, Daniel Wik, V. Antoniou, M. Eracleous, Ann Hornschemeier, Margaret Lazzarini, Bret D. Lehmer, Neven Vulic, Benjamin F. Williams, T. J. Maccarone, K. Pottschmidt, Andrew Ptak, Mihoko Yukita, Andreas Zezas

Physics Faculty Publications and Presentations

Using hard (E > 10 keV) X-ray observations with NuSTAR, we are able to differentiate between the accretion states, and thus compact object types, of neutron stars (NSs) and black holes (BHs) in X-ray binaries (XRBs) in M31, our nearest Milky Way–type neighbor. Using 10 moderate-depth (20–50 ks) observations of the disk of M31 covering a total of ∼0.45 deg², we detect 20 sources at 2σ in the 4–25 keV bandpass, 14 of which we consider to be XRB candidates. This complements an existing, deeper (100–400 ks) survey covering ∼0.2 deg² of the bulge and the …

The Nature Of X-Rays From Young Stellar Objects In The Orion Nebula Cluster—A Chandra Hetgs Legacy Project, Norbert S. Schulz, David P. Huenemoerder, David A. Principe, Marc Gagné, Hans Mortiz Günther, Joel Kastner, Joy Nichols, Andrew Pollock, Thomas Preibisch, Paola Testa, Fabio Reale, Fabio Favata, Claude R. Canizares

Earth & Space Sciences Faculty Publications

The Orion Nebula Cluster (ONC) is the closest site of very young (∼1 Myr) massive star formation The ONC hosts more than 1600 young and X-ray bright stars with masses ranging from ∼0.1–35 Me. The Chandra HETGS Orion Legacy Project observed the ONC with the Chandra High Energy Transmission Grating Spectrometer (HETGS) for 2.1 Ms. We describe the spectral extraction and cleaning processes necessary to separate overlapping spectra. We obtained 36 high-resolution spectra, which include a high-brilliance X-ray spectrum of θ1 Ori C with over 100 highly significant X-ray lines. The lines show Doppler broadening between 300 and 400 km …

Role Of Planetary Wave-Tide-Gravity Wave Interactions In Whole Atmosphere Coupling, Zishun Qiao

Doctoral Dissertations and Master's Theses

This dissertation investigates the mechanism by which the Earth's whole atmosphere couples from the bottom to the top, pole to pole. The work in this dissertation utilizes observational data and numerical simulations, with a particular emphasis on sudden stratospheric warming (SSW) events. The development of a new multi-static meteor radar at 30ºS, named Chilean Observation Network De MeteOr Radars (CONDOR), provides a key dataset for the present studies. Wind validation of this new radar system is performed across different sites and compared to a co-located sodium lidar. Wave-wave interactions in the mesosphere and lower thermosphere (MLT) that may be responsible …

Equilibria And Effective Transition Rates In Linear Networks, Sayani Ghosh

All Dissertations

Investigating equilibration in nucleosynthetic processes is crucial for understanding stellar chemical abundances in nuclear astrophysical scenarios. While current computational models are effective at predicting final species abundances at the end of these stellar processes, they fail to provide insights into the evolution of equilibrium. Without this deeper understanding, it is challenging to determine the impact of individual reaction rates on timescales and the resultant equilibrium.

In this work, we model nucleosynthetic processes as directed graphs. We develop theorems that allow us to express the mass fractions of species as spanning arborescences of these graphs. By obtaining eigenvalues in terms of …

An Analysis Of The Propagation Of Gravitational Radiation Under A Graviton Of Nonzero Mass And Its Implications For Cosmological Measurements, Margaret Johnston

UNLV Theses, Dissertations, Professional Papers, and Capstones

Under the assumptions of General Relativity (GR), gravitational waves propagate at the speed of light and their mediation can be represented as a particle through a massless graviton. We investigate the impact and observability of the presence of a massive graviton, how such a modification to GR would also modify the observed gravitational waves from astrophysical sources, and how this effect can be used as an independent measurement of cosmmological parameters, including the Hubble parameter H0. We simulate the impact of a massive graviton on compact binary coalescence observation in a near-future LIGO-Virgo-KAGRA interferometer network through a modification to the …

Temperature-Dependent Optical Constants Of Vanadium Dioxide Thin Films Deposited On Polar Dielectrics, Imtiaz Ahmad, Satya R. Kachiraju, Sundar Kunwar, Zachary M. Brown, Pinku Roy, Matthew Gaddy, Vladimir Kuryatkov, Yejin Kwon, Ayrton A. Bernussi, Myoung-Hwan Kim

Physics & Astronomy Faculty Publications

Coating polar dielectrics with thin film vanadium dioxide (VO2) enables one to exploit the temperature-dependent phase transition within VO2 to actively tune and modulate surface phonon polaritons at mid-infrared. However, controlling the behavior of such systems requires intimate knowledge of the temperature-dependent optical constants of VO2, which depend greatly on the growth conditions and substrate material. Here, we accurately determine the complex optical constants of VO2 on polar dielectrics across the insulator-to-metal phase transition (IMT) using only normal incident reflectance spectra by analyzing the reflectance with Kramers–Kronig relations and thin film Fresnel equations. This non-ellipsometry technique offers an …

Observation Of Gravitational Waves From The Coalescence Of A 2.5–4.5 M⊙ Compact Object And A Neutron Star, A. Abac, R. Abbott, I. Abouelfettouh, F. Acernese, Teviet Creighton, Mario C. Diaz, Francisco Llamas, Soma Mukherjee, Volker Quetschke, Wenhui Wang

Physics & Astronomy Faculty Publications

We report the observation of a coalescing compact binary with component masses 2.5–4.5 M⊙ and 1.2–2.0 M⊙ (all measurements quoted at the 90% credible level). The gravitational-wave signal GW230529_181500 was observed during the fourth observing run of the LIGO–Virgo–KAGRA detector network on 2023 May 29 by the LIGO Livingston observatory. The primary component of the source has a mass less than 5 M⊙ at 99% credibility. We cannot definitively determine from gravitational-wave data alone whether either component of the source is a neutron star or a black hole. However, given existing estimates of the maximum neutron star mass, we find …

Answers To Frequently Asked Questions About The Pulsar Timing Array Hellings And Downs Curve, Joseph D. Romano, Bruce Allen

Physics & Astronomy Faculty Publications

We answer frequently asked questions (FAQs) about the Hellings and Downs correlation curve—the ‘smoking-gun’ signature that pulsar timing arrays (PTAs) have detected gravitational waves (GWs). Many of these questions arise from inadvertently applying intuition about the effects of GWs on LIGO-like detectors to the case of pulsar timing, where not all of it applies. This is because Earth-based detectors, like LIGO and Virgo, have arms that are short (km scale) compared to the wavelengths of the GWs that they detect (≈102–104 km). In contrast, PTAs respond to GWs whose wavelengths (tens of light-years) are much shorter than their arms (a …

Space Radiation Assessment And Mitigation: Meeting The Growing Demand For Shielding Solutions By Enhancing Models And Exploring Novel Shielding Opportunities, M. Laura Sorgi Johann

Doctoral Dissertations and Master's Theses

The rapid growth of satellite technology and the increasing presence of vulnerable technology and human life in space have highlighted the need for improved shielding materials. Industry standard protocols for shielding are being pushed to their limits as we gain a deeper understanding of the harsh space environment and as chip sizes approach the scale of radiation wavelengths. Furthermore, the commercialization of space is attracting interest from industries such as pharmaceuticals and semiconductor crystal growing, as they explore the potential benefits of zero-gravity production environments. However, the eagerness to develop lighter shielding and the lack of consideration for existing tools …

Constraining Giant Planet Occurrence Rates With The Multi-Band Imaging Survey For High-Alpha Planets (Mishaps) Observations Of 47 Tucanae, Alison Crisp

LSU Doctoral Dissertations

Though the confirmed exoplanet population has now reached over 5,500 planets, we still have a plethora of unanswered questions, e.g., regarding their formation mechanisms, true demographics, occurrence rates, and habitability. One remaining question is whether hot Jupiters formed in situ or migrated to their current orbits, so close to their host stars that their periods are 10 days or less. This question can potentially be answered by probing the effects of elemental abundances on hot Jupiter occurrence rates. These rates have been found to correlate with metallicity, but the specific elements responsible for the correlation have largely been unresolved. The …

Glitch Veto Based On Unphysical Gravitational Wave Binary Inspiral Templates, Raghav Girgaonkar, Soumya D. Mohanty

Physics & Astronomy Faculty Publications

Transient signals arising from instrumental or environmental factors, commonly referred to as glitches, constitute the predominant background of false alarms in gravitational wave searches with ground-based detectors. Therefore, effective data analysis methods for vetoing glitch-induced false alarms are crucial to enhancing the sensitivity of a search. We present a veto method for glitches that impact matched filtering-based searches for binary inspiral signals. The veto uses unphysical sectors in the space of chirp time parameters as well as an unphysical extension including negative chirp times to efficiently segregate glitches from gravitational wave signals in data from a single detector. Inhabited predominantly …

Identifying The O’Connell Effect In Eclipsing Binary Stars, Nicholas Paolella

Computer Science and Information Technology Faculty

Data science techniques have wide-ranging applications throughout scientific explorations. One, is filtering astronomical data to better understand specific populations, such as binary stars. Specifically, binary stars that exhibit the O’Connell effect are worthy of study as this phenomenon is still not well understood. The O’Connell effect can be defined as the asymmetry of maxima in the light curves, as captured by the instrument, while observing the eclipsing binary system in question. There is significant data captured by NASA and curated by Villanova University, which enabled the investigation of eclipsing binary stars and the attributes of which may help identify the …

Variable Radio Emission Of Neutron Star X-Ray Binary Ser X–1 During Its Persistent Soft State, Eli C. Pattie, Thomas J. Maccarone, Alexandra J. Tetarenko, James C. A. Miller-Jones, Manuel Pichardo Marcano, Liliana E. Rivera Sandoval

Physics & Astronomy Faculty Publications

Ser X–1 is a low-mass neutron star X-ray binary and has been persistently accreting since its discovery in the 1960s. It has always been observed to be in a soft spectral state and has never showed substantial long-term X-ray variability. Ser X–1 has one previous radio observation in the literature in which radio emission was detected during this soft state, which is contrary to the behavior of black hole X-ray binaries. We have recently obtained 10 randomly sampled radio epochs of Ser X–1 in order to further investigate its anomalous soft-state radio emission. Out of 10 epochs, we find 8 …

Calibrating The Global Network Of Gravitational Wave Observatories Via Laser Power Calibration At Nist And Ptb, Dripta Bhattacharjee, Richard Lenox Savage, Rishabh Bajpai, Joseph Betzwieser, Vladimir Bossilkov, Dan Chen, Cervane Grimaud, Shingo Hido, Sudarshan Karki, Francisco Llamas

Physics & Astronomy Faculty Publications

Current gravitational wave (GW) observatories rely on photon calibrators that use laser radiation pressure to generate displacement fiducials used to calibrate detector output signals. Reducing calibration uncertainty enables optimal extraction of astrophysical information such as source distance and sky position from detected signals. For the ongoing O4 observing run that started on 24 May 2023, the global GW detector network is employing a new calibration scheme with transfer standards calibrated at both the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). These transfer standards will circulate between the observatories and the metrology institutes to provide laser …

Evaluating Spatial Clustering As A Lunar Crater Classification Method, Annalyse Dickinson

Physics and Astronomy Summer Fellows

Crater identification is important for investigating and determining the age of planetary surfaces. Based on the number of primary craters—which are formed from a bolide impacting a planetary surface—one can determine the surface’s absolute model age, but the secondary craters—which are formed from the many fragments ejected during a primary crater’s creation—contaminate that count. The abundant variability in crater identification methods is a prominent issue in the field of planetary science. In addition, there is no single characteristic that can set these craters apart due to the processes involved in their formation and degradation. This is why we aim to …

Lunar Crater Categorization And Why Accessibility Matters For Planetary Scientists, Gavin Soueidan, Mckenzie Snyder

Physics and Astronomy Summer Fellows

One can determine the absolute model age of any planetary body in the solar system by compiling statistics about primary craters. However, secondary craters contaminate those statistics. Differentiating between primary craters—which are formed from an impact of an object from space onto a planetary surface—and secondary craters—which are formed from the fragments ejected from primaries—is an outstanding question in planetary science literature. No one characteristic can universally distinguish primaries from secondaries, and workers have developed numerous methods for sorting the two classes of craters. This is why we are developing a semi-automated, transparent, reproducible procedure that will compile datasets that …

Satellite Group Infall Into The Milky Way: Exploring The Crater-Leo Case With New Hst Proper Motions, Stacy S. Mcgaugh

Faculty Scholarship

Context. Within Λ cold dark matter (ΛCDM) simulations, Milky Way-like galaxies accrete some of their satellite galaxies in groups of 3–5 members rather than individually, and this has been suggested as a possible mechanism driving the formation of satellite planes. Objects accreted in groups are expected to share similar specific total energy and angular momentum, and to also have identical orbital planes and directions. Aims. Looking at observatio ns of Milky Way satellites, the dwarf galaxies Leo II, IV, V, and Crater II, and the star cluster Crater 1 were proposed to be a vestige of group infall. The suggested …

Fe-Rich X-Ray Amorphous Material Records Past Climate And Persistence Of Water On Mars, Anthony D. Feldman, Elisabeth M. Hausrath, Elizabeth B. Rampe, Valerie Tu, Tanya S. Peretyazhko, Christopher Defelice, Thomas Sharp

Geoscience Faculty Research

X-ray amorphous material comprises 15-73 wt.% of sedimentary rocks and eolian sediments in Gale crater. This material is variably siliceous and iron rich but aluminum poor. The presence of volatiles is consistent with the existence of incipient weathering products. To better understand the implications of this material for past aqueous conditions on Mars, here we investigate X-ray amorphous material formation and longevity within terrestrial iron rich soils with varying ages and environmental conditions using bulk and selective dissolution methods, X-ray diffraction, and transmission electron microscopy. Results indicate that in situ aqueous alteration is required to concentrate iron into clay-size fraction …

Numerical Simulations Suggest Asteroids (101955) Bennu And (162173) Ryugu Are Likely Second Or Later Generation Rubble Piles., K J Walsh, R-L Ballouz, W F Bottke, C Avdellidou, Harold Connolly Jr., M Delbo, D N Dellagiustina, E R Jawin, T Mccoy, P Michel, T Morota, M C Nolan, S R Schwartz, S Sugita, D S Lauretta

School of Earth & Environment Departmental Research

Rubble pile asteroids are widely understood to be composed of reaccumulated debris following a catastrophic collision between asteroids in the main asteroid belt, where each disruption can make a family of new asteroids. Near-Earth asteroids Ryugu and Bennu have been linked to collisional families in the main asteroid belt, but surface age analyses of each asteroid suggest these bodies are substantially younger than their putative families. Here we show, through a coupled collisional and dynamical evolution of members of these families, that neither asteroid was likely to have been created at the same time as the original family breakups, but …

Rising Tides: An Analytic Modeling Code Of Tidal Effects In Binary Neutron Star Mergers, Alexander O'Dell, Maria Babiuc-Hamilton

Physics Faculty Research

Gravitational waves produced by binary neutron star mergers offer a unique window into matter behavior under extreme conditions. In this context, we analytically model the effect of matter on gravitational waves from binary neutron star mergers. We start with a binary black hole system, leveraging the post-Newtonian formalism for the inspiral and the Backwards-one-Body model for the merger. We combine the two methods to generate a baseline waveform and we validate our results against numerical relativity simulations. Next, we integrate tidal effects in phase and amplitude to account for matter and spacetime interaction using the NRTidal model and test its …