Astrophysics and Astronomy Commons^™

Local Time Asymmetry Of Saturn's Magnetosheath Flows, B. Burkholder, P. A. Delamere, X. Ma, M. F. Thomsen, R. J. Wilson, F. Bagenal

Publications

Using gross averages of the azimuthal component of flow in Saturn's magnetosheath, we find that flows in the prenoon sector reach a maximum value of roughly half that of the postnoon side. Corotational magnetodisc plasma creates a much larger flow shear with solar wind plasma prenoon than postnoon. Maxwell stress tensor analysis shows that momentum can be transferred out of the magnetosphere along tangential field lines if a normal component to the boundary is present, i.e., field lines which pierce the magnetopause. A Kelvin‐Helmholtz unstable flow gives rise to precisely this situation, as intermittent reconnection allows the magnetic field to …

On Orientation Memory In High Density Polyethylene - Carbon Nanofibers Composites, Mircea Chipara, Brian Jones, Dorina M. Chipara, Jianhua Li, Karen Lozano, Shah Valloppilly, David Sellmyer

Physics & Astronomy Faculty Publications

An orientation memory effect in high density polyethylene (HDPE) filled with vapor grown carbon nanofibers (VGCNF) is reported. Two-dimensional X-ray (2DXR) confirmed the reorientation of HDPE crystallites upon the uniaxial stretching of HDPE and HDPE filled by VGCNFs. This anisotropy of 2DXR spectra was decreased by heating all stretched samples (loaded or not loaded by VGCNFs) from room to the melting temperature of HDPE. Upon cooling these samples to room temperature, it was noticed that only the nanocomposite retained a weak partial (uniaxial) order, while HDPE showed a completely isotropic 2DXR spectrum. It was concluded that during the stretching of …

Wideband Photometry Of Saturn In 2008-2009, Richard W. Schmude Jr.

Georgia Journal of Science

A total of 52 brightness measurements of Saturn were made during its 2008-2009 apparition. (An apparition is the time interval between when the planet is in conjunction with the Sun to the next time that it is conjunction with the Sun.) The selected normalized magnitudes of Saturn for b = 3.0° are B(1,0) = -7.87 ± 0.02, V(1,0) = - 9.00 ± 0.01, R(1,0) = -9.62 ± 0.01 and I(1,0) = -9.63 ± 0.01. (I have defined b as the square root of the absolute value of the product of the Saturnicentric latitude of the Earth and of the Sun; …

A Photometric Approach To The Redshift Of Galaxies, John Bohman, Joseph Moody

Journal of Undergraduate Research

It is necessary to study the distribution of matter to better understand the universe. There are many difficulties associated with this task however, one of the most basic being that that the universe is an extremely large space, and it takes a lot of time and effort to observe faint objects. Multi fiber spectrometers have made this task much easier, and over 1.4 million spectroscopic redshifts have been obtained. While this is certainly impressive, much remains to be done. This project attempts to develop a survey method capable of detecting and finding the redshift of relatively close (meaning a redshift …

Identifying Binary Brown Dwarf Systems Using Model Point Spread Functions, Kyle Matt, Denise Stephens

Journal of Undergraduate Research

The purpose of this project was to improve upon a method for discovering binary brown dwarf systems, and create a program to speed up the implementation of that method. A Brown Dwarf (BD) is a celestial object that is not massive enough to undergo hydrogen fusion in its core, meaning it is too small to be a star, but is also too big to be a planet. BDs can form in low-mass binary pairs. A stellar object located many parsecs away will act as a point source of light for an observer on Earth, therefore the light from such an …

Machine Learning With Scattering Transforms, Jacob Hansen, Gus Hart

Journal of Undergraduate Research

Our goal was to implement scattering transforms as a mathematical representation of materials. The intention of this project was to build intuition on this technique using model data in one and two dimensions. The tools created here will be used as templates in further projects on real materials data. The intuition built during this project is crucial to the machine learning framework for materials design that we hope to build in the near future.

Full-Disk Wideband Photometry Of The Moon: R And I Filter Measurements, Richard W. Schmude Jr.

Georgia Journal of Science

A total of 42 full-disk brightness measurements of our Moon are reported. These measurements include the entire lunar disk including the Earthlit portion. All measurements were made on the Johnson R (red) and I (infrared) system and were fitted to cubic equations. The results are summarized in this report. The selected normalized magnitudes of the Moon are R(1,0) = -0.70 ± 0.10 and I(1,0) = -1.12 ± 0.06. The selected geometric albedo is 0.18 ± 0.01 for the Johnson R and I system.

A Giant Planet Undergoing Extreme-Ultraviolet Irradiation By Its Hot Massive-Star Host, B. S. Gaudi, K. G. Stassun, K. A. Collins, T. G. Beatty, G. Zhou, D. W. Latham, A. Bieryla, J. D. Eastman, R. J. Siverd, J. R. Crepp, E. J. Gonzales, D. J. Stevens, L. A. Buchhave, J. Pepper, M. C. Johnson, K. D. Colón, Eric L.N. Jensen, J. E. Rodriguez, V. Bozza, S. C. Novati, G. D’Ago, M. T. Dumont, T. Ellis, C. Gaillard, H. Jang-Condell, D. H. Kasper, A. Fukui, J. Gregorio, A. Ito, J. F. Kielkopf, M. Manner, K. Matt, N. Narita, T. E. Oberst, P. A. Reed, G. Scarpetta, D. C. Stephens, R. R. Yeigh, R. Zambelli, B. J. Fulton, A. W. Howard, D. J. James, M. Penny, D. Bayliss, I. A. Curtis, D. L. Depoy, G. A. Esquerdo, A. Gould, M. D. Joner, R. B. Kuhn, J. Labadie-Bartz, M. B. Lund, J. L. Marshall, K. K. Mcleod, R. W. Pogge, H. Relles, C. Stockdale, T. G. Tan, M. Trueblood, P. Trueblood

Physics & Astronomy Faculty Works

The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extrasolar planets now known, only six have been found that transit hot, A-type stars (with temperatures of 7,300–10,000 kelvin), and no planets are known to transit the even hotter B-type stars. For example, WASP-33 is an A-type star with a temperature of about 7,430 kelvin, which hosts the hottest known transiting planet, WASP-33b (ref. 1); the planet is itself as hot as a red dwarf star of type M (ref. 2). WASP-33b displays a large heat …

Some Recent Studies Of Mars: The North Polar Cap, Cecropia And Hellas, Richard W. Schmude Jr.

Georgia Journal of Science

This paper summarizes changes on Mars which occurred in 2014. Images recorded by the Mars Reconnaissance Orbiter’s MARCI camera (hereafter MRO) and those made from the Earth are examined. It is concluded a spiral-shaped cloud of water ice crystals developed and moved eastward at an average speed of 1.7 m/s, a temporary isolated bright patch in Cecropia developed and one or more dust storms developed at the NPC edge near 83° N, 320° W. Measurements of the boundary of a white area in Hellas are consistent with it not changing as the year, season or time of day progressed. This …

The North Polar Cap Of Mars, Richard W. Schmude Jr.

Georgia Journal of Science

During late 2013 and early 2014, the Northern Hemisphere of Mars faced Earth. This provided a prime opportunity for studying its North Polar Cap (NPC). The writer measured the cap size during the intervals 30° < L_s < 70° and 82° < L_s < 134°. (The areocentric longitude of the Sun from Mars is designated as Ls and it determines the seasons on that planet; essentially, the beginning of the northern spring, summer, fall and winter are at L_s = 0°, 90°, 180° and 270°). NPC latitude measurements were made with the software package WinJupos. The mean latitudes were measured for 23 four-degree intervals of L_s. Wilcoxon Signed Rank Tests at the 90% confidence level are consistent with there being no statistical difference between the NPC in 2000 and both 2013 and 2011-2012 for 30° < L_s < 70°. Based on this same test there is a statistical difference for the NPC in 2002 and 2009-2010 compared to 2000. Therefore, it is concluded that the NPC may show interannual differences. Essentially, the NPC stopped shrinking at L_s = 82°. …

Search For Gravitational Waves From Scorpius X-1 In The First Advanced Ligo Observing Run With A Hidden Markov Model, B. P. Abbott, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov

Physics & Astronomy Faculty Publications

Results are presented from a semicoherent search for continuous gravitational waves from the brightest low-mass X-ray binary, Scorpius X-1, using data collected during the first Advanced LIGO observing run. The search combines a frequency domain matched filter (Bessel-weighted F-statistic) with a hidden Markov model to track wandering of the neutron star spin frequency. No evidence of gravitational waves is found in the frequency range 60-650 Hz. Frequentist 95% confidence strain upper limits, h095%=4.0×10-25, 8.3×10-25, and 3.0×10-25 for electromagnetically restricted source orientation, unknown polarization, and circular polarization, respectively, are reported at 106 Hz. They are ≤10 times higher than the theoretical …

Dissipationless Hall Current In Dense Quark Matter In A Magnetic Field, Efrain J. Ferrer, Vivian De La Incera

Physics & Astronomy Faculty Publications

We show the realization of axion electrodynamics within the Dual Chiral Density Wave phase of dense quark matter in the presence of a magnetic field. The system exhibits an anomalous dissipationless Hall current perpendicular to the magnetic field and an anomalous electric charge density. Connection to topological insulators and 3D optical lattices, as well as possible implications for heavy-ion collisions and neutron stars are outlined.

Magnetic Fields Threading Black Holes: Restrictions From General Relativity And Implications For Astrophysical Black Holes, David Garofalo

Faculty Articles

The idea that black hole spin is instrumental in the generation of powerful jets in active galactic nuclei and X-ray binaries is arguably the most contentious claim in black hole astrophysics. Because jets are thought to originate in the context of electromagnetism, and the modeling of Maxwell fields in curved spacetime around black holes is challenging, various approximations are made in numerical simulations that fall under the guise of ‘ideal magnetohydrodynamics’. But the simplifications of this framework may struggle to capture relevant details of real astrophysical environments near black holes. In this work, we highlight tension between analytic and numerical …

Mechanosensing Of Shear By Pseudomonas Aeruginosa Leads To Increased Levels Of The Cyclic-Di-Gmp Signal Initiating Biofilm Development, Christopher A. Rodesney, Brian Roman, Numa Dhamani, Benjamin J. Cooley, Ahmed Touhami, Vernita D. Gordon

Physics & Astronomy Faculty Publications

Biofilms are communities of sessile microbes that are phenotypically distinct from their genetically identical, free-swimming counterparts. Biofilms initiate when bacteria attach to a solid surface. Attachment triggers intracellular signaling to change gene expression from the planktonic to the biofilm phenotype. For Pseudomonas aeruginosa, it has long been known that intracellular levels of the signal cyclic-di-GMP increase upon surface adhesion and that this is required to begin biofilm development. However, what cue is sensed to notify bacteria that they are attached to the surface has not been known. Here, we show that mechanical shear acts as a cue for surface adhesion …

Searching For Signals Of Dark Matter Decay, Gardner R. Marshall, William Hester

Journal of the South Carolina Academy of Science

Dark matter is believed to make up approximately eighty-three percent of the matter in the universe. Despite its apparent abundance, it has not yet been directly detected, and it is not known what types of particles it is composed of. Efforts to understand what dark matter is made of and how it fits into the Standard Model of particle physics is currently an important and active area of research. In this paper we investigate a method of studying dark matter indirectly by using terrestrial neutrino telescopes to search for signs of dark matter decay. In particular, we study leptonically decaying …

Gw170104: Observation Of A 50-Solar-Mass Binary Black Hole Coalescence At Redshift 0.2, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, B. Hughey, J. W. W. Pratt, E. Schmidt, G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10∶11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31.2 þ8.4 −6.0M⊙ and 19.4 þ5.3 −5.9M⊙ (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, …

Sobel, Dava. The Glass Universe: How The Ladies Of The Harvard Observatory Took The Measure Of The Stars. New York: Viking, 2016. 324 Pp. $30.00 Hardcover (Isbn 9780670016952)., Aldemaro Romero Jr.

Publications and Research

Women in science have been and are still facing numerous obstacles. According

to the American Association of University Professors, despite the fact that 60

percent of all doctoral students (the main pipeline for academia) in this country

are women, only 46 percent of assistant professors, 38 percent of associate

professors, and 23 percent of full professors are female. On top of that, women

faculty in colleges and universities in the United States earn on average 10 percent

less than their male counterparts.1 A number of studies have shown that women

in academia suffer from lower expectations for intelligence, so when …

Characterizing Cool Brown Dwarfs And Low-Mass Companions With Low-Resolution Near-Infrared Spectra, Paige Godfrey

Dissertations, Theses, and Capstone Projects

Exoplanet direct detections are reaching the temperature regime of cool brown dwarfs, motivating further understanding of the coolest substellar atmospheres. These objects, T and Y dwarfs, are numerous and isolated in the field, thus making them easier to study in detail than objects in companion systems. Brown dwarf spectral types are derived from spectral morphology and generally appear to correspond with decreasing mass and effective temperature (T_eff). However, spectral subclasses of the colder objects do not share this monotonic temperature correlation, indicating that secondary parameters (gravity, metallicity, dust) significantly influence spectral morphology. These secondary atmospheric parameters can provide …

Electromagnetic Radio Frequency Heating In The Pulsed Electric Current Sintering (Pecs) Process, Yufei Liu, D. H. Liebenberg

Publications

Pulsed electric current sintering offers rapid sintering of many materials compared with hot press sintering. Earlier studies had demonstrated that neither sparks nor plasma formation occur in a typical apparatus such as Dr. Sinter™. Hitchcock et al. showed that electromagnetic radio frequency (rf) emission occurred during the pulsing current and suggested this emission was a relevant augmentation to the hot press sintering in addition to the current flow in the specimen. In this report the importance of rf emission in the sintering process is demonstrated and opportunities to further exploit this approach to improve the sintering process are suggested.

Kelt-18b: Puffy Planet, Hot Host, Probably Perturbed, K. K. Mcleod, J. E. Rodriguez, R. J. Oelkers, K. A. Collins, A. Bieryla, B. J. Fulton, K. G. Stassun, B. S. Gaudi, K. Penev, D. J. Stevens, K. D. Colón, J. Pepper, N. Narita, R. Tsuguru, A. Fukui, P. A. Reed, B. Tirrell, T. Visgaitis, J. F. Kielkopf, David H. Cohen, Eric L.N. Jensen, J. Gregorio, Ö. Baştürk, T. E. Oberst, C. Melton, E. M.-R. Kempton, A. Baldrige, Y. S. Zhao, R. Zambelli, D. W. Latham, G. A. Esquerdo, P. Berlind, M. L. Calkins, A. W. Howard, H. Isaacson, L. M. Weiss, P. Benni, T. G. Beatty, J. D. Eastman, M. T. Penny, R. J. Siverd, M. B. Lund, J. Labadie-Bartz, G. Zhou, I. A. Curtis, M. D. Joner, M. Manner, H. Relles, G. Scarpetta, D. C. Stephens, C. Stockdale, T. G. Tan, D. L. Depoy, J. L. Marshall, R. W. Pogge, M. Trueblood, P. Trueblood

Physics & Astronomy Faculty Works

We report the discovery of KELT-18b, a transiting hot Jupiter in a 2.87-day orbit around the bright ( V = 10.1), hot, F4V star BD+60 1538 (TYC 3865-1173-1). We present follow-up photometry, spectroscopy, and adaptive optics imaging that allow a detailed characterization of the system. Our preferred model fits yield a host stellar temperature of K and a mass of , situating it as one of only a handful of known transiting planets with hosts that are as hot, massive, and bright. The planet has a mass of , a radius of , and a density of , making it …