Astrophysics and Astronomy Commons^™

Planetarium Show: “One Sky”, Jim & Linda Lee Planetarium

International Education Week

Look beyond borders and experience the wonder of the universe in One Sky. This planetarium presentation offers a captivating opportunity to explore the night sky and reflect on the shared world we all inhabit.

Exploring The Dynamics Of Tilted, Truncated Accretion Disks, José L. Montés, Chris Fragile, Deepika Bollimpalli, Matthew Liska

Journal of the South Carolina Academy of Science

Tilted accretion disks are theoretically not uncommon in stellar mass black hole systems. The dynamics of tilted disks display interesting physical behaviors that could explain certain observational phenomena such as quasi-periodic oscillations. We present results of recent numerical simulations of tilted, truncated accretion disks around rotating black holes. Our simulations model systems composed of a thick inner torus surrounded by a thin outer disk and were run with the goal of investigating the behaviors of the torus because of the exchange of angular momentum between it and the outer disk. Multiple simulations produced surprising results, such as the potential tearing …

Astrophysical Radiative Capture Reaction Rates In Light Nuclei: A Review Of Results From The Modified Potential Cluster Model, S. B. Dubovichenko, B. M. Yeleusheva, A. S. Tkachenko, R. Ya. Kezerashvili

Publications and Research

A review of results obtained within a single theoretical framework—the Modified Potential Cluster Model (MPCM)—is presented for astrophysical radiative capture reactions involving the lightest and 1p-shell nuclei. The approach has been applied to reactions relevant to the r-process, the CNO and HCNO cycles, and parts of the Big Bang nucleosynthesis (BBN) and post-BBN scenarios. The model incorporates the classification of orbital states according to Young’s diagrams and has been successfully applied to describe the available experimental data on the total cross sections of the radiative capture of neutrons, protons, and the lightest clusters by 40 light nuclei at astrophysical energies. …

Detector Orientation Matters: Consequences For Gravitational-Wave Background Detectability, Nelson Christensen, Joseph D. Romano, Mairi Sakellariadou, Jishnu Suresh

Physics & Astronomy Faculty Publications

Cross-correlation searches for gravitational-wave backgrounds depend on the geometrical configuration (physical separation and relative orientation) of the detectors comprising the network. Applying standard techniques to a few simple examples, we illustrate how the relative orientation of a pair of Earth-based L-shaped laser interferometers can drastically impact the detectability of both isotropic and anisotropic gravitational-wave backgrounds.

Where Are Linearized Gauge Invariants Encoded For Plane Waves In Linearized Gravity, Ramesh Radhakrishnan, David Mcnutt, Delaram Mirfendereski, Eric Davis, William Julius, Gerald Cleaver

Physics & Astronomy Faculty Publications

In this work we will investigate the structures of invariants within the class of plane waves in linearized General Relativity, to introduce a new approach to determine the linearized gauge invariants encoding the polarization of the plane waves. The Newman–Penrose (NP) formalism is traditionally used to analyze the polarization content of gravitational waves, while the gauge-invariant Bardeen formalism provides a complementary description based on the irreducible scalar, vector, and tensor perturbations of the metric. We will apply the Bardeen formalism to compute all scalar, vector, and tensor gauge-invariant variables explicitly and verify that only the two transverse–traceless tensor modes survive. …

An Ion-Neutral Reaction To Form Cyanobenzene And Ethynylbenzene In Titan’S Atmosphere, Rachel M. Huchmala, Vincent J. Esposito

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The ion-neutral reaction between cyanoacetylene (HC₃N) and phenyl anion (C₆H₅^–) leads to the formation of cyanobenzene (C₆H₅CN) and the ethynyl anion (C₂H^–) via a submerged, exothermic pathway. Through a different mechanism, the same two reactants also form ethynylbenzene (C₆H₅C₂H) and CN^–. These new reactions can be a foundation for the production of substituted benzenes using molecules currently present on Saturn’s largest moon, Titan. Cyclic aromatic molecules like C₆H₅CN and C₆H_{5 …}

K 1-6 Is A Photoionised Interstellar Medium Nebula Shaped By A Fast-Moving Hot White Dwarf In A Triple System, Jaroslav Merc, David Jones, Ana Escorza, Henri M. J. Boffin, Nicole Reindl, Michael Abdul-Masih, Thomas Masseron, Paulina Sowicka, Jan Kára, Jorge Jorge García-Rojas

Physics & Astronomy Faculty Publications

Aims. K 1-6 has long been classified as a planetary nebula (PN) hosting a binary central star; however, it has remained poorly studied due to its faintness. The central star exhibits pronounced photometric variability whose origin is still unclear. We present a comprehensive characterisation of the K 1-6 system, including the physical properties of its stellar components and the nature of the surrounding nebulosity.

Methods. We conducted a multi-wavelength analysis combining optical and UV spectroscopy obtained with the Gran Telescopio Canarias, the Telescopio Nazionale Galileo, the Nordic Optical Telescope, and the Hubble Space Telescope. We also present long-term multi-band ground- …

Fully Anharmonic Infrared Spectra Of Neutral Polycyclic Aromatic Hydrocarbons With Up To 38 Carbons, Nolan J. H. White, Vincent J. Esposito, Christiaan Boersma, Louis J. Allamandola, Jesse D. Bregman, Alexandros Maragkoudakis, Pasquale Temi, Ryan Fortenberry

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Interstellar aromatic infrared band (AIB) spectra show agreement with presently computed anharmonic spectra for various types of polycyclic aromatic hydrocarbons (PAHs) determined using a novel semiempirical quantum chemical method. Since the AIB spectrum is a blend of emission spectra from a vast number of different PAHs, likely with an array of different molecular structures, the spectra for a sample set of 31 PAHs ranging in size from naphthalene (C₁₀H₈) up to circumbiphenyl (C₃₈H₁₆) are combined, giving consideration to almost all PAH structural motifs. The computed numerical quartic force fields coupled to second-order …

Infrared Spectroscopy And Photochemistry Of Aromatic Nitriles In Para-Hydrogen Matrices, Sam Mcgrath, Vincent J. Esposito, Linshan Zeng, Thomas H. Speak, Brendan Moore, Pavle Djuricanin, Jun Miyazaki, Takamasa Momose, Ilsa R. Cooke

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Motivated by recent detections of several aromatic nitriles in Taurus Molecular Cloud 1, we report laboratory and theoretical investigations of the vibrational spectroscopy and photochemistry of singly and doubly cyanosubstituted benzene in solid para-hydrogen matrices. We compare the photochemistry of cyanobenzene (benzonitrile) and three dicyanobenzene isomers initiated by excitations at 193 nm. In addition, we report the photochemistry of deuterated cyanobenzene (d5-cyanobenzene), enabling us to determine the major products produced during the cyanobenzene photodissociation. The major products observed in the photolysis of all the nitriles are HCN and HNC, which are likely produced by hydrogen abstraction from para-hydrogen by the …

Cedar: Investigating The Mesosphere And Lower Thermosphere Neutral Temperature And Winds Responses To Geomagnetic Storms Equatorward Of The Auroral Zone, Tao Yuan

Funded Research Records

No abstract provided.

The Jwst Weather Report: Unravelling The Atmospheric Variability Of Isolated Worlds Using Principal Component Analysis, Merle A. Schrader, Johanna M. Vos, Evert Nasedkin, Jennifer Kestell, Nicolas B. Cowan, Roman Akhmetshyn, Samuel Beiler, Beth A. Biller, Ben Burningham, Jacqueline Faherty, Eileen C. Gonzales, Allison M. Mccarthy, Caroline V. Morley, Barry O'Donovan, Cian O'Toole, Genaro Suárez, Xianyu Tan, Channon Visscher, Niall Whiteford, Yifan Zhou

Faculty Work Comprehensive List

Brown dwarf variability directly probes atmospheric dynamics beyond the Solar System, and recent James Webb Space Telescope (JWST) time-resolved spectroscopy has opened a new window into these processes. Principal component analysis (PCA) offers a data-driven framework to identify the dominant, independent patterns of spectral variability of variable targets without relying on prior atmospheric assumptions. simp (simp) is a young, T2.5, brown dwarf at the planetary-mass boundary, making it an ideal analogue for directly imaged exoplanets. We analysed one rotation of JWST/NIRSpec PRISM time-series spectroscopy to investigate the drivers of its variability using PCA. Prior analyses of these data revealed …

Δ−Scuti Star Hr 1170, Salman A. Nejad

Aquila: The Journal of Embry-Riddle Observatory

HR 1170, a variable star in the constellation Perseus, exhibits multi-periodic pulsations consistent with its classification as a δ−Scuti star. Through photometric and spectroscopic observations using the 1-meter ERAU telescope and the SARA-RM telescope, this study investigates its variability and spectral characteristics. Photometry conducted over several nights reveals pulsation periods that closely align with previously reported values. Time-resolved spectroscopy highlights prominent absorption features, including Balmer lines and metallic elements, offering further insights into the star’s atmospheric dynamics.

A Multiwavelength Study Of A Long-Duration Very-High-Energy Flare From Bl Lacertae With Veritas, Avery Archer, Et Al.

Physics & Astronomy Faculty publications

We report the first observations of a long-duration very-high-energy (VHE; E>100 GeV) flare from BL Lacertae (VER J2202+422), taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). On 2022 October 15, the Fermi-Large Area Telescope (LAT) detected elevated GeV activity originating from this blazar. This triggered a multiwavelength campaign, which includes observations from VERITAS, Swift, NuSTAR, and select optical and radio observatories. VERITAS observed the source for a total of ∼9.8 hr between 2022 September 1 and 2022 December 1. An analysis of these data yields a ∼28σ detection of the source. While previously observed VHE …

Commissioning And Performance Characterization Of An Elevator Loading System For The Ucnτ+ Magneto-Gravitational Trap, Alexander Komives, Et Al.

Physics & Astronomy Faculty publications

We report the first commissioning with ultracold neutrons (UCN) of an elevator-based loading system for the UCNτ magneto-gravitational neutron trap at Los Alamos Neutron Science Center. The system replaces the previous trap-door geometry with a moving bin designed to transfer UCN from UCN guide height into the open trap while reducing their kinetic energy through an adiabatic expansion of the accessible volume. UCN cutoff energy scans, direct leakage measurements, and variable bin-hold cycle measurements were used to characterize the incident spectrum and the loading losses. Successive sealing modifications increased the effective bin population lifetime from 26.69 ± 0.62 to 47.64 …

Toward The Study Of Photon Dynamics In Non-Separable Spacetimes, Kara Nelson

Graduate Masters Theses

Black holes provide a unique laboratory for testing general relativity in the strong-field regime through observations such as black hole images and gravitational wave signals. Comparing theoretical predictions with these observations requires accurate numerical models of photon trajectories. This thesis develops and validates a generalized ray-tracing framework for computing null geodesics in stationary, axisymmetric spacetimes. Unlike many existing ray-tracing methods, the framework does not rely on metric separability or analytic solutions, allowing it to be applied to both separable and non-separable spacetimes. The framework is validated by reproducing known Schwarzschild and Kerr results and is applied to a quasi-Kerr spacetime …

Benchmark Brown Dwarf Systems. I. Chemical Abundance Analysis Of Fgk Stars With Wide-Separation Brown Dwarf Companions Using Pepsi, Caprice L. Phillips, Megan Bedell, Catherine Manea, Alison Duck, Anusha Pai Asnodkar, Emily J. Griffith, Austin Rothermich, Emily Calamari, Jacqueline K. Faherty, Ben Burningham, Channon Visscher, Eileen C. Gonzales, Ilya Ilyin, Klaus Strassmeier, Ji Wang

Faculty Work Comprehensive List

We present results from a spectroscopic survey of 32 FGK stars hosting brown dwarfs, using high-resolution optical spectra (R = 130,000 and 50,000) obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument spectrograph on the Large Binocular Telescope. The primary goal of this survey is to determine precise stellar parameters and abundances for 11 elements (C, O, Mg, Si, Ca, Al, Ti, Fe, Y, S, and N) in these systems. We employ spectral synthesis within the BACCHUS framework to derive precise stellar properties and elemental abundance ratios. For our data with average signal-to-noise ratio > 200, we achieve a typical …

Temperature Predictions With Zncuins/Zns Quantum Dots, Reu/Fri Program Physics And Astronomy, Amber Banks

Student Works

For hundreds of years, humans have built thermometers based on the principles of thermal expansion and contraction. In the modern world, there is a need to scale down our thermometers to monitor cellular reactions, both within the human body and within artificial organ chips. Lewis et al. (2020) introduces a nanoscale thermometer based on the thermal expansion of CdTe quantum dots. When ex panded, these dots exhibit systematic changes in photoluminescence (PL) which are recognized by a neural network as an increase in temperature. Our research builds upon the framework of Lewis et al. (2020), testing its feasibility with ZnCuInS/ZnS …

Field-Like- And Self-Spin-Orbit Torques In Magnetic Multilayer Films, Kyle Jeffrey Peterson

Electronic Theses and Dissertations

Spin-orbit torques (SOTs) have been realized as an energy efficient mechanism to manipulate and drive magnetization dynamics in magnetic multilayer films. Their damping-like and field-like components provide distinct pathways for controlling the magnetization, enabling switching, sustaining magneto-oscillations, and driving domain-wall motion with potential applications in nonvolatile memory, spin-based logic, and microwave signal generation. However, the accurate quantification and interpretation of these torques remains complicated by experimental sensitivity, the co-symmetry of the Oersted field and the effective field due to the field-like torque, and assumptions regarding the material layers from which the torques originate. The body of work set forth in …

Extreme Geomagnetic Storm Effects On Earth's Radiation Belts Observed By Calet On The International Space Station, Anthony W. Ficklin

LSU Doctoral Dissertations

This dissertation examines changes in Earth's energetic-particle environment using measurements from the Calorimetric Electron Telescope (CALET) on the International Space Station. Although CALET was designed primarily for high-energy cosmic-ray and gamma-ray observations, its count rates provide nearly continuous measurements of particles of ~1 MeV and above. The analysis uses the CHDX, CHDY, and IMC4X channels, which have approximate electron thresholds of $>\!1.5$, $\!>3.4$, and $\!>8.2$~MeV and proton thresholds of $>\!17$, $\!>37$, and $\!>52$~MeV, respectively. Because these measurements do not identify particle species, the observations are interpreted using their geographic and geomagnetic distributions, the relative …

Tidal Evolution Of Packed Moon Systems Around An Earth-Mass Planet, Alan Briseño, Billy Quarles, Marialis Rosario-Franco

Student Publications

While missions have long targeted terrestrial exoplanets within the habitable zone of their host stars, the number of exomoon candidates is expected to grow as next generation space-based observatories achieve the photometric sensitivity required to detect their transit signals. Constraining the stability limits of tightly packed moon systems is therefore essential for transit searches and predicting the number of moons around terrestrial planets. In our solar system, only three moons orbit the terrestrial planets, motivating the question of whether Earth-mass exoplanet systems can sustain long-lived, tightly packed satellites. We investigate the stability limits of an Earth-mass planet orbiting a Sun-mass …