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Articles 31 - 60 of 1497
Full-Text Articles in Physical Sciences and Mathematics
Stellar Atmosphere Models For Select Veritas Stellar Intensity Interferometry Targets, Jackson Ladd Sackrider, Jason P. Aufdenberg, Katelyn Sonnen
Stellar Atmosphere Models For Select Veritas Stellar Intensity Interferometry Targets, Jackson Ladd Sackrider, Jason P. Aufdenberg, Katelyn Sonnen
Beyond: Undergraduate Research Journal
Since 2020 the Very Energetic Radiation Imaging Telescope Array System (VERITAS) has observed 48 stellar targets using the technique of Stellar Intensity Interferometry (SII). Angular diameter measurements by VERITAS SII (VSII) in a waveband near 400 nm complement existing angular diameter measurements in the near-infrared. VSII observations will test fundamental predictions of stellar atmosphere models and should be more sensitive to limb darkening and gravity darkening effects than measurements in the near-IR, however, the magnitude of this difference has not been systematically explored in the literature. In order to investigate the synthetic interferometric (as well as spectroscopic) appearance of stars …
3d Mhd Models Of The Centrifugal Magnetosphere From A Massive Star With An Oblique Dipole Field, Asif Ud-Doula, Stanley P. Owocki, Marc Gagné, Simon Daley-Yates
3d Mhd Models Of The Centrifugal Magnetosphere From A Massive Star With An Oblique Dipole Field, Asif Ud-Doula, Stanley P. Owocki, Marc Gagné, Simon Daley-Yates
Earth & Space Sciences Faculty Publications
We present results from new self-consistent 3D magnetohydrodynamics(MHD)simulations of the magnetospheres from massive stars with a dipole magnetic axis that has a non-zero obliquity angle (β) to the star’s rotation axis. As an initial direct application, we compare the global structure of co-rotating discs for nearly aligned (β = 5◦) versus half-oblique (β = 45◦) models, both with moderately rapid rotation (∼0.5 critical). We find that accumulation surfaces broadly resemble the forms predicted by the analytical rigidly rotating magnetosphere model, but the mass buildup to near the critical level for centrifugal breakout against magnetic confinement distorts the field from the …
Nearby Galaxies: Modelling Star Formation Histories And Contamination By Unresolved Background Galaxies, Hadi Papei
Nearby Galaxies: Modelling Star Formation Histories And Contamination By Unresolved Background Galaxies, Hadi Papei
Electronic Thesis and Dissertation Repository
Galaxies are complex systems of stars, gas, dust, and dark matter which evolve over billions of years, and one of the main goals of astrophysics is to understand how these complex systems form and change. Measuring the star formation history of nearby galaxies, in which thousands of stars can be resolved individually, has provided us with a clear picture of their evolutionary history and the evolution of galaxies in general.
In this work, we have developed the first public Python package, SFHPy, to measure star formation histories of nearby galaxies using their colour-magnitude diagrams. In this algorithm, an observed colour-magnitude …
Impact On Infinite Asteroids: Analysis Of Ejecta Outcomes In Small Body Binary Systems, Jennifer Larson
Impact On Infinite Asteroids: Analysis Of Ejecta Outcomes In Small Body Binary Systems, Jennifer Larson
Electronic Theses and Dissertations, 2020-2023
Binary asteroid systems make up roughly 15% of objects occupying near-Earth space, the Main Belt, and trans-Neptunian space. The impact history of asteroids in binary systems represents an interesting aspect of the general problem pertaining to the nature and evolution of surfaces for such objects. Specifically, the post-impact dynamics of ejecta and its relation to surface modification is a challenging question owing, in part, to the unusual gravitational field in a binary system and the subsequent capture and emplacement of debris on either binary component. Observable differences or similarities between the two bodies in the color, reflectance, thermal properties, and …
Towards A Prototype Paleo-Detector For Supernova Neutrino And Dark Matter Detection, Emilie Marie Lavoie-Ingram
Towards A Prototype Paleo-Detector For Supernova Neutrino And Dark Matter Detection, Emilie Marie Lavoie-Ingram
UNF Graduate Theses and Dissertations
Using ancient minerals as paleo-detectors is a proposed experimental technique expected to transform supernova neutrino and dark matter detection. In this technique, minerals are processed and closely analyzed for nanometer scale damage track remnants from nuclear recoils caused by supernova neutrinos and possibly dark matter. These damage tracks present the opportunity to directly detect and characterize the core-collapse supernova rate of the Milky Way Galaxy as well as the presence of dark matter. Current literature presents theoretical estimates for these potential tracks, however, there is little research investigating the experimental feasibility of this technique. At the University of North Florida, …
S-Type Stars: Line List For The A²Π-X²Σ⁺ Band System Of Lao, P. F. Bernath, R. Dodangodage, J. Liévin
S-Type Stars: Line List For The A²Π-X²Σ⁺ Band System Of Lao, P. F. Bernath, R. Dodangodage, J. Liévin
Chemistry & Biochemistry Faculty Publications
LaO bands are found in the spectra of cool S-type stars. The bands of the A2Π–X2Σ+ transition with v' ⩽ 3 and v'' ≤ 4 are rotationally analyzed, providing spectroscopic constants for the A2Π state. Line strengths are calculated using an ab initio transition dipole moment function, and radiative lifetimes for the A2Π state have also been computed. A line list for the A2Π–X2Σ+ transition of LaO is provided and can be used to determine LaO stellar abundances.
Astr 1: General Astronomy, David Goldberg
Astr 1: General Astronomy, David Goldberg
Open Educational Resources
No abstract provided.
A Multidimensional View On The Emission-Line Diagnostics Of The Warm Ionized Gas In Nearby Galaxies, Xihan Ji
A Multidimensional View On The Emission-Line Diagnostics Of The Warm Ionized Gas In Nearby Galaxies, Xihan Ji
Theses and Dissertations--Physics and Astronomy
The baryonic cycle, being a fundamental process that shapes the cosmic ecosystem, describes the transformation and migration of baryonic matter in different phases. The warm ionized interstellar medium (ISM), defined as low-density gas that has temperature of the order of 10,000 K, represents an important link of the baryonic cycle and can be produced by a variety of energetic activities in galaxies, such as star formations, active galactic nuclei, and so forth. More importantly, the formation and evolution of the warm ionized gas not only traces the ongoing activities of the galaxies, but also reveals the past evolution of galaxies …
The Radial Quenching Progression Of Nearby Galaxies, Chenyu Zhao
The Radial Quenching Progression Of Nearby Galaxies, Chenyu Zhao
Theses and Dissertations--Physics and Astronomy
In this dissertation, we explore the spatial distribution of quiescent regions within galaxies using data from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory (SDSS-IV MaNGA). Our analysis focuses on a radial range spanning from 0.3 R e to 1.2 R e and involves the development of innovative data selection and processing methods. Through this investigation, we identify two prominent types of transition galaxies: central-star-forming galaxies (C-SF galaxies) and central-quiescent galaxies (C-Q galaxies). Notably, we observe a correlation between galaxy mass and the predominant type of transition, with more massive galaxies tending to be C-Q …
Development Of Regolith Simulants Of Lunar Permanently Shadowed Regions And Jupiter Trojan Asteroids, Karlis Slumba
Development Of Regolith Simulants Of Lunar Permanently Shadowed Regions And Jupiter Trojan Asteroids, Karlis Slumba
Electronic Theses and Dissertations, 2020-2023
Every scientific experiment or innovation goes through a phase of testing equipment. This is not only true for experiments in the laboratory, but also very relevant for experiments on other planetary bodies. In order to test tools and robotic equipment that are destined for another planet, moon, asteroid or comet, it is necessary to simulate the regolith environment on that surface. In this thesis we have provided an overview of two methods for regolith simulant development. In one approach we made simulants in different compositions to find the best spectral fit to Jupiter Trojan asteroids. At visible to near-infrared (VNIR) …
Physical Properties And Chemical Composition Of Comets, Olga Harrington
Physical Properties And Chemical Composition Of Comets, Olga Harrington
Electronic Theses and Dissertations, 2020-2023
Comets and Centaurs are icy remnants from the formation of the solar system. Analyzing the physical properties of their nuclei and their production rates can serve as powerful tools for tracing primitive solar system material. The four research projects in this dissertation examine these properties in comets and Centaurs. The first project focuses on observations of main belt comet 176P/LINEAR that were obtained with the Kepler space telescope. Optical lightcurves were used to constrain models of the nucleus's spin pole axis, shape and activity level. The second project used millimeter-wavelength spectra from the Arizona Radio Observatory Submillimeter Telescope and infrared …
A Theoretical Study Of Elementary Processes In Interstellar Plasma, Joshua Forer
A Theoretical Study Of Elementary Processes In Interstellar Plasma, Joshua Forer
Graduate Thesis and Dissertation 2023-2024
Interstellar plasma — interstellar clouds in particular — play an important role in determining the structure and evolution of galaxies. Understanding the time evolution of such plasmas requires knowledge of the chemical processes that drive their dynamics. Two processes are studied in this dissertation: radiative electron attachment (REA) via dipole-bound states (DBSs) and dissociative recombination (DR). Of the several hundred molecules detected in the interstellar medium, only eight anions have been detected: CN-, C3N-, C5N-, C7N-, C4H-, C6H-, C8H-, and C10H-. Their production mechanism is not well known; REA was suggested as a possible formation pathway, but previous theoretical studies …
Clusters, Curves, And Centroids: Stellar Flare Morphology In The Ultraviolet, Vera Berger
Clusters, Curves, And Centroids: Stellar Flare Morphology In The Ultraviolet, Vera Berger
Pomona Senior Theses
With a novel sample of 495 high-cadence light curves for stellar flares in the near-ultraviolet, I explore similarity measures, clustering algorithms, averaging methods, and curve fitting techniques for time series. This work seeks to provide insight into whether stellar flares are similar across stars, if we can identify physically meaningful patterns in their light curves, and how to construct a comprehensive model for flares. I construct the first empirical template for flare light curves in the ultraviolet, and compute ``average elements" of flares displaying complex features such as quasi-periodic oscillations and multipeak structures. Developing accurate models for flares in the …
Two Substellar Survivor Candidates; One Found And One Missing, T. Von Hippel, N. Walters, J. Farihi, T.R. Marsh, E. Breedt, P.W. Cauley, J.J. Hermes
Two Substellar Survivor Candidates; One Found And One Missing, T. Von Hippel, N. Walters, J. Farihi, T.R. Marsh, E. Breedt, P.W. Cauley, J.J. Hermes
Publications
This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the benchmark brown dwarf has ��2 = 68 ± 8 MJup, ��eff ≈ 2100 K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 …
The Analysis Of Radio And X-Ray Energetics Of Fast Radio Bursts, Emily Huerta
The Analysis Of Radio And X-Ray Energetics Of Fast Radio Bursts, Emily Huerta
Undergraduate Research Symposium Posters
Here, we analyze the graphs and figures presented in Laha et al. (2022) and compare their slopes to our figures. Laha et al. (2022) includes two graphs, one that shows a comparison between radio fluence vs. x-ray fluence and radio energy vs. x-ray energy. In these graphs, the slopes are anywhere from 3.3e-14 to 2e-5, which are much less than unity. Our figures are consistent with these values, also providing slopes anywhere between the same range. Strong limits on this ratio between radio and x-ray energetics can either support the magnetar progenitor model, or completely dismiss it. Since we found …
Interdisciplinary Convergence To God: A Supplement To The Big Bang & God– An Astro-Theology, Theodore Walker
Interdisciplinary Convergence To God: A Supplement To The Big Bang & God– An Astro-Theology, Theodore Walker
Perkins Faculty Research and Special Events
Here is a December 2022 supplement to the 2015 book—The Big Bang and God: An Astro-Theology wherein an astronomer and a theologian offer a study of interdisciplinary convergences with natural theology both in the scientific researches of Sir Fred Hoyle and in the philosophical researches of Charles Hartshorne and Alfred North Whitehead, thereby illustrating a constructive postmodern trend (New York: Palgrave Macmillan, 2015) by Theodore Walker Jr. and Chandra Wickramasinghe, with editing and co-authoring by Alexander Vishio.
Biology, astronomy, astrobiology, cosmology, and theology converge when the word “God” refers to “that than which none greater can conceived” (St. Anselm), …
A Method For Exploring The Habitability Of Earth-Like Exoplanets: Applications To Tess Objects Of Interest 203 B, 256 B, And 700 D, Paul Bonney
Graduate Theses and Dissertations
The Transiting Exoplanet Survey Satellite (TESS) has and is continuing to discover a multitude of potentially habitable planet candidates. As more planets are detected and confirmed, it becomes increasingly important to strategically search for signs of habitability with which to differentiate and prioritize them for further observation, in particular with the James Webb Space Telescope (JWST). To facilitate this, I have created a method for prioritizing TESS planet candidates based on parameters derived from their light curves and have applied the method to the TESS Candidate Target List (CTL). This data set uses preliminary fits to transit modeling which can …
The Evolution Of X-Ray Binaries And Their Accretion States, Lacey A. West
The Evolution Of X-Ray Binaries And Their Accretion States, Lacey A. West
Graduate Theses and Dissertations
X-ray binary systems (XRBs) consist of a compact object component (e.g., black hole or neutron star) that accretes matter from a companion star. Although the extent to which XRBs contributed to the early heating of the intergalactic medium is still under investigation, it is estimated that XRBs dominated the X-ray radiation field before the reionization epoch. The study of XRB emission is therefore crucial to our understanding of the very early universe. Furthermore, studying the abundance and radial distribution of each XRB type within a galaxy can be revealing of the host galaxy’s local properties, structure, and evolution. XRB spectra …
First-Principles Study Of Doping Effects On Ferroelectricity And On Rashba Spin Splitting, Zegnet Yimer Muhammed
First-Principles Study Of Doping Effects On Ferroelectricity And On Rashba Spin Splitting, Zegnet Yimer Muhammed
Graduate Theses and Dissertations
In this dissertation, we have thoroughly studied the effect of chemical and charge dopingon ferroelectrics (PbTiO3 and BaTiO3) and Rashba type semiconductor (BiTeI). In the first project, We investigate the polar instability and soft modes in electron-doped PbTiO3 using linear-response density functional calculations. Because, metallicity and ferroelectric-like polar distortion are mutually non-compatible, and their coexistence in the same system is an intriguing subject of fundamental interest in the field of structure phase transition. However, it is unclear what mechanism may extend the limit of metallicity that allows polar distortion. We find that ferroelectric instability can remarkably sustain up to an …
Orbital Mapping Of Seasonal And Yearly Changes In Co2 And Water Ice On The Southern Polar Cap Of Mars, Victoria Michell Ann Karnes
Orbital Mapping Of Seasonal And Yearly Changes In Co2 And Water Ice On The Southern Polar Cap Of Mars, Victoria Michell Ann Karnes
Graduate Theses and Dissertations
This research exhibits a new foundation for the rates of change in CO2 and water ice on the southern polar cap of Mars, where the annual precipitation cycles are known to fluctuate seasonally between the north and south pole, based on observations from the Compact Reconnaissance Imaging Spectrometer (CRISM). The conventional belief is that both CO2 ice and water ice on the southern polar cap condenses and evaporates over the course of a Martian year (MY), condensing during the Martian spring and summer and evaporating during the Martian fall and winter. With this theory in mind, CO2 and water ice …
Deciphering Surfaces Of Trans-Neptunian And Kuiper Belt Objects Using Radiative Scattering Models, Machine Learning, And Laboratory Experiments, Al Emran
Graduate Theses and Dissertations
Decoding surface-atmospheric interactions and volatile transport mechanisms on trans-Neptunian objects (TNOs) and Kuiper Belt objects (KBOs) involves an in-depth understanding of physical and thermal properties and spatial distribution of surface constituents – nitrogen (N2), methane (CH4), carbon monoxide (CO), and water (H2O) ices. This thesis implements a combination of radiative scattering models, machine learning techniques, and laboratory experiments to investigate the uncertainties in grain size estimation of ices, the spatial distribution of surface compositions on Pluto, and the thermal properties of volatiles found on TNOs and KBOs. Radiative scattering models (Mie theory and Hapke approximations) were used to compare single …
Probing The Extent Of Vertical Mixing In Brown Dwarf Atmospheres With Disequilibrium Chemistry, Sagnick Mukherjee, Jonathan J. Fortney, Natasha E. Batalha, Theodora Karalidi, Mark S. Marley, Channon Visscher, Brittany E. Miles, Andrew J. I. Skemer
Probing The Extent Of Vertical Mixing In Brown Dwarf Atmospheres With Disequilibrium Chemistry, Sagnick Mukherjee, Jonathan J. Fortney, Natasha E. Batalha, Theodora Karalidi, Mark S. Marley, Channon Visscher, Brittany E. Miles, Andrew J. I. Skemer
Faculty Work Comprehensive List
Evidence of disequilibrium chemistry due to vertical mixing in the atmospheres of many T- and Y-dwarfs has been inferred due to enhanced mixing ratios of CO and reduced NH3. Atmospheric models of planets and brown dwarfs typically parameterize this vertical mixing phenomenon with the vertical eddy diffusion coefficient, Kzz. While Kzz can perhaps be approximated in the convective regions in the atmosphere with mixing length theory, in radiative regions, the strength of vertical mixing is uncertain by many orders of magnitude. With a new grid of selfconsistent 1D model atmospheres from Teff of 400–1000 K, computed with a new radiative-convective …
A Comparative L-Dwarf Sample Exploring The Interplay Between Atmospheric Assumptions And Data Properties, Eileen C. Gonzales, Ben Burningham, Jacqueline K. Faherty, Nikole K. Lewis, Channon Visscher, Mark Marley
A Comparative L-Dwarf Sample Exploring The Interplay Between Atmospheric Assumptions And Data Properties, Eileen C. Gonzales, Ben Burningham, Jacqueline K. Faherty, Nikole K. Lewis, Channon Visscher, Mark Marley
Faculty Work Comprehensive List
Comparisons of atmospheric retrievals can reveal powerful insights on the strengths and limitations of our data and modeling tools. In this paper, we examine a sample of five L dwarfs of similar effective temperature (Teff) or spectral type to compare their pressure–temperature (P-T) profiles. Additionally, we explore the impact of an object's metallicity and the signal-to-noise ratio (S/N) of the observations on the parameters we can retrieve. We present the first atmospheric retrievals: 2MASS J15261405+2043414, 2MASS J05395200−0059019, 2MASS J15394189−0520428, and GD 165B increasing the small but growing number of L dwarfs retrieved. When compared to the atmospheric retrievals …
Stacking The Gamma-Ray Sky To Search For Faint Astrophysical Populations, Yuzhe Song
Stacking The Gamma-Ray Sky To Search For Faint Astrophysical Populations, Yuzhe Song
Dissertations, Theses, and Capstone Projects
Gamma-ray emission can be generated from a wide variety of high-energy astrophysical phenomena, from stellar flares to pulsating neutron stars, and from interstellar clouds to the center of the Milky Way Galaxy. Entering the 13th year of its orbit around Earth, the Fermi Space Gamma-ray Telescope has been continually surveying the γ-ray sky with its Large Area Telescope (LAT) on board. The latest Fermi source catalog contains over 6000 sources. Yet, a lot of sources that are expected to emit γ-rays are not detected, and only small percentages of some populations are detected. For example, solar flares are detected in …
Reverberation Mapping Of Markarian 421 Using V,R, I, And Ha Filters, Alex Whitman
Reverberation Mapping Of Markarian 421 Using V,R, I, And Ha Filters, Alex Whitman
Honors Program Theses and Projects
Active Galactic Nuclei (AGN) at their most basic level are supermassive blackholes that emit light. While that sounds paradoxical, it speaks volumes to how little we know about these extraordinary objects. One technique that can be used, and was used here to better understand these objects is reverberation mapping. We employed this method on the AGN Markarian 421 (Mrk 421) at Bridgewater State University (BSU). Mrk 421 was chosen because it is the brightest known AGN, averaging 12.7 magnitudes, and the observational abilities of BSU are best suited for objects brighter than 18 magnitudes in optical wavelengths. We observed Mrk …
Where Are The Habitable Planets In Our Local Group Of Galaxies?, William C. Windsor
Where Are The Habitable Planets In Our Local Group Of Galaxies?, William C. Windsor
Undergraduate Student Research Internships Conference
No abstract provided.
X-Ray Properties Of Early-Type Stars In The Tarantula Nebula From T-Rex, Paul A. Crowther, Patrick S. Broos, Leisa K. Townsley, Andy M. T. Pollock, Katie A. Tehrani, Marc Gagné
X-Ray Properties Of Early-Type Stars In The Tarantula Nebula From T-Rex, Paul A. Crowther, Patrick S. Broos, Leisa K. Townsley, Andy M. T. Pollock, Katie A. Tehrani, Marc Gagné
Earth & Space Sciences Faculty Publications
We reassess the historical L-X/L-Bol relation for early-type stars from a comparison between T-ReX, the Chandra ACIS X-ray survey of the Tarantula Nebula in the Large Magellanic Cloud (LMC), and contemporary spectroscopic analysis of massive stars obtained primarily from VLT/FLAMES, VLT/MUSE, and HST/STIS surveys. For 107 sources in common (some host to multiple stars), the majority of which are bolometrically luminous (40 per cent exceed 10(6)L(circle dot)), we find an average log L-X/L-Bol = -6.90 +/- 0.65. Excluding extreme systems Mk 34 (WN5h+WN5h), R140a (WC4+WN6+), and VFTS 399 (O9 IIIn+?), plus four WR sources with anomalously hard X-ray components (R130, …
Unlocking The Mystery Of Tev J2032+4130 Through Veritas Data, Devon J. Barros
Unlocking The Mystery Of Tev J2032+4130 Through Veritas Data, Devon J. Barros
Honors Program Theses and Projects
TeVJ2032+4130 is a high energy celestial object that emits Very High Energy (VHE) gamma rays and is located in the star forming region of the Cygnus constellation. It was first detected by the High Energy Gamma Ray Astronomy (HEGRA) experiment. Later observations from the Very Energetic Radiation Imaging Telescope Array System (VERITAS2014) were used to determine that the gamma-ray emission from the source could be coming from a Pulsar Wind Nebula (PWN) powered by a binary pulsar named PSR J2032+4127. For the PWN scenario, VERITAS predicted a cutoff in the gamma-ray spectrum above 10 TeV. Using ~33 hours of VERITAS …
The Cosmic History Of X-Ray Binary Evolution, Woodrow Gilbertson
The Cosmic History Of X-Ray Binary Evolution, Woodrow Gilbertson
Graduate Theses and Dissertations
The Chandra Deep Fields provide an extraordinary window into the high-energy history of the cosmos. Observations of non-active galaxies within the deep fields can be leveraged to extract information about the formation and evolution of X-ray binaries (XRBs). Previous studies have suggested that the evolution of XRB luminosity can be expressed a function of physical parameters such as star formation rate, stellar mass, stellar age, and metallicity. The goal of this work is to develop and implement a complete physical parameterization for the luminosity of XRB populations, which can be utilized for a variety of further studies.
Chapter 1 provides …
Revisit Of Open Clusters Upk 39, Upk 41 And Phoc 39 : A New Binary Open Cluster Found, Xianhao Ye, Terry D. Oswalt, Jingkun Zhao, Yong Yang, Gang Zhao
Revisit Of Open Clusters Upk 39, Upk 41 And Phoc 39 : A New Binary Open Cluster Found, Xianhao Ye, Terry D. Oswalt, Jingkun Zhao, Yong Yang, Gang Zhao
Publications
We investigate the three open clusters near Aquila Rift cloud, named as UPK 39 (c1 hereafter), UPK 41 (c2 hereafter) in Sim et al. (2019) and PHOC 39 (c3 hereafter) in Hunt & Reffert (2021), respectively. Using photometric passpands, reddening, and extinction from Gaia DR3, we construct the color-absolute-magnitude diagram (CAMD). Using isochrone fits their ages are estimated as 6.3 ± 0.9, 8.1 ± 1.4 and 21.8 ± 2.2 Myr, respectively. Their proper motions and radial velocities, estimated using data from Gaia and LAMOST are very similar. From their orbits, relative distances among them at different times, kinematics, ages, and …