Astrophysics and Astronomy Commons^™

Titan’S Variable Ionosphere During The T118 And T119 Cassini Flybys, N. J. T. Edberg, E. Vigren, Darci Snowden, L. H. Regoli, O. Shebanits, J.-E. Wahlund, D. J. Andrews, C. Bertucci, J. Cui

All Faculty Scholarship for the College of the Sciences

We report on unusual dynamics in Titan’s ionosphere as a significant difference in ionospheric electron density is observed between the T118 and T119 Cassini nightside flybys. Two distinct nightside electron density peaks were present during T118, at 1,150 and 1,200 km, and the lowest density ever observed in Titan’s ionosphere at altitudes 1,000–1,350 km was during T118. These flybys were quite similar in geometry, Saturn local time, neutral density, extreme ultraviolet flux, and ambient magnetic field conditions. Despite this, the Radio and Plasma Waves/Langmuir Probe measured a density difference up to a factor of 6 between the passes. The overall …

Survival Of Non-Coplanar, Closely Packed Planetary Systems After A Close Encounter, David R. Rice, Frederic A. Rasio, Jason H. Steffen

Physics & Astronomy Faculty Research

Planetary systems with more than two bodies will experience orbital crossings at a time related to the initial orbital separations of the planets. After a crossing, the system enters a period of chaotic evolution ending in the reshaping of the system’s architecture via planetary collisions or ejections. We carry out N-body integrations on a large number of systems with equally spaced planets (in units of the Hill radius) to determine the distribution of instability times for a given planet separation. We investigate both the time to the initiation of instability through a close encounter and the time to a planet--planet …

Magnetothermal Disc Winds In X-Ray Binaries: Poloidal Magnetic Fields Suppress Thermal Winds, Tim Waters, Daniel Proga

Physics & Astronomy Faculty Research

Magnetic, radiation pressure, and thermal driving are the three mechanisms capable of launching accretion disc winds. In X-ray binaries, radiation pressure is often not significant, as in many systems the luminosity is too low for driving due to continuum transitions yet too high for driving due to line transitions. This leaves thermal and magnetic driving as the contender launching mechanisms in these systems. Using ATHENA++, we perform axisymmetric ideal MHD simulations that include radiative heating and cooling processes appropriate for Compton heated winds to show that the inclusion of magnetic fields into a thermally driven wind has the opposite effect …

Database Review: Sao/Nasa Astrophysics Data System, Laura Pope Robbins

Publications

Laura Pope Robbins is an advisor for The Charleston Advisor, and the review below is included in Scholarly Commons with the permission of the publisher.

The Astrophysics Data System (ADS) is the premier Open Access research database for astronomy and astrophysics containing over 13 million bibliographic records. These records include journal articles, books, conference proceedings, historical observatory bulletins, and other gray literature. An exceptional feature of ADS is the visualizations it creates, showing author networks, overlapping citations, and frequently occurring terminology giving researchers new ways to explore the literature. It is a unique resource that is as easy for a …

Light Curves In X-Rays And Gamma-Rays, Daniel H. Sellers

STAR Program Research Presentations

Gamma-ray Bursts are the most luminous and energetic events in the universe. Understanding the intrinsic properties of GRBs allows for their use as standard candles (objects of known distance and luminosity) and for the study of extremely distant regions of space.

In this study we use the piecewise Willingale model to fit the X-ray flux vs. time curves (light curves) of 235 GRBs with detectable 'plateau' phase and known redshift using data from the swift repository. This sample is analyzed for consistency with a relation between the temporal decay and spectral indexes predicted by the Fireball model of GRB Emission. …

Underwater Adhesive Using Solid–Liquid Polymer Mixes, Alin Cristian Chipara, T. Tsafack, P. S. Owuor, J. Yeon, C. E. Junkermeier, A. C. T. Van Duin, S. Bhowmick, S. A. S. Asif, S. Radhakrishnan, Mircea Chipara

Physics & Astronomy Faculty Publications

Instantaneous adhesion between different materials is a requirement for several applications ranging from electronics to biomedicine. Approaches such as surface patterning, chemical cross-linking, surface modification, and chemical synthesis have been adopted to generate temporary adhesion between various materials and surfaces. Because of the lack of curing times, temporary adhesives are instantaneous, a useful property for specific applications that need quick bonding. However, to this day, temporary adhesives have been mainly demonstrated under dry conditions and do not work well in submerged or humid environments. Furthermore, most rely on chemical bonds resulting from strong interactions with the substrate such as acrylate …

E-Hooks Provide Guidance And A Soft Landing For The Microtubule Binding Domain Of Dynein, Nayere Tajielyato, Lin Li, Yunhui Peng, Joshua Alper, Emil Alexov

Publications

Macromolecular binding is a complex process that involves sensing and approaching the binding partner, adopting the proper orientation, and performing the physical binding. We computationally investigated the role of E-hooks, which are intrinsically disordered regions (IDRs) at the C-terminus of tubulin, on dynein microtubule binding domain (MTBD) binding to the microtubule as a function of the distance between the MTBD and its binding site on the microtubule. Our results demonstrated that the contacts between E-hooks and the MTBD are dynamical; multiple negatively charted patches of amino acids on the E-hooks grab and release the same positively charged patches on the …

Identifying Weak Interdomain Interactions That Stabilize The Supertertiary Structure Of The N-Terminal Tandem Pdz Domains Of Psd-95, Inna S. Yanez Orozco, Frank A. Mindlin, Junyan Ma, Bo Wang, Brie Levesque, Matheu Spencer, Soheila Rezaei Adariani, George Hamilton, Feng Ding, Mark E. Bowen, Hugo Sanabria

Publications

Previous studies of the N-terminal PDZ tandem from PSD-95 produced divergent models and failed to identify interdomain contacts stabilizing the structure. We used ensemble and single-molecule FRET along with replica-exchange molecular dynamics to fully characterize the energy landscape. Simulations and experiments identified two conformations: an open-like conformation with a small contact interface stabilized by salt bridges, and a closed-like conformation with a larger contact interface stabilized by surface-exposed hydrophobic residues. Both interfaces were confirmed experimentally. Proximity of interdomain contacts to the binding pockets may explain the observed coupling between conformation and binding. The low-energy barrier between conformations allows submillisecond dynamics, …

Origins Of Ultradiffuse Galaxies In The Coma Cluster – I. Constraints From Velocity Phase Space, Adebusola Alabi, Anna Ferré-Mateu, Aaron Romanowsky, Jean Brodie, Duncan Forbes, Asher Wasserman, Sabine Bellstedt, Ignacio Martín-Navarro, Viraj Pandya, Maria Stone, Nobuhiro Okabe

Faculty Publications

We use Keck/DEIMOS spectroscopy to confirm the cluster membership of 16 ultradiffuse galaxies (UDGs) in the Coma cluster, bringing the total number of spectroscopically confirmed UDGs from the Yagi et al. (Y16) catalogue to 25. We also identify a new cluster background UDG, confirming that most (∼95 per cent) of the UDGs in the Y16 catalogue belong to the Coma cluster. In this pilot study of Coma UDGs in velocity phase space, we find evidence of a diverse origin for Coma cluster UDGs, similar to normal dwarf galaxies. Some UDGs in our sample are consistent with being late infalls into …

Photoproduction Of K+ K- Meson Pairs On The Proton, S. Lombardo, M. Battaglieri, A. Celentano, A. D'Angelo, R. De Vita, A. Filippi, D. I. Glazier, M. Khachatryan, A. Klein, Y. Prok, The Clas Collaboration

Physics Faculty Publications

The exclusive reaction γp → pK⁺K⁻ was studied in the photon energy range 3.0–3.8 GeV and momentum transfer range 0.6 < −t< 1.3 GeV². Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20 pb⁻¹. The reaction was isolated by detecting the K⁺ and the proton in CLAS, and reconstructing the K⁻ via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the ϕ meson in the P wave, …

Fitting Parameter Uncertainties In Least Squares Fitting, R. Steven Turley

Faculty Publications

This article review the theory and practice of computing uncertainties in the fit parameters in least squares fits. It shows how to estimate the uncertainties and gives some numerical examples in Julia of their use. Examples are given and validated for both linear and nonlinear fits.

Polynomial Fitting, R. Steven Turley

Faculty Publications

This article reviews the theory and some good practice for fitting polynomials to data. I show by theory and example why fitting using a basis of orthogonal polynomials rather than monomials is desirable. I also show how to scale the independent variable for a more stable fit. I also demonstrate how to compute the uncertainty in the fit parameters. Finally, I discuss regression analysis: how to determine whether adding an additional term to the fit is justified.

A Derivation Of Fluidic Maxwell-Proca Equations For Electrodynamics Of Superconductors & Its Implication To Chiral Cosmology Model, Florentin Smarandache, Victor Christianto, Yunita Umniyati

Branch Mathematics and Statistics Faculty and Staff Publications

Mario Liu described a hydrodynamic Maxwell equations [3] and, also discussed potential implications of these new approaches to superconductors which were made after Tajmar’s paper [4]. In this paper, we present for the first time a derivation of fluidic Maxwell-Proca equations. The name of fluidic Maxwell-Proca is proposed because the equations were based on modifying Maxwell-Proca and Hirsch’s theory of electrodynamics of superconductor. It is hoped that this paper may stimulate further investigations and experiments in superconductor. It may be expected to have some impact to cosmology modeling too, for instance we consider a hypothetical argument that photon mass can …

From Thermal Dissociation To Condensation In The Atmospheres Of Ultra Hot Jupiters: Wasp-121b In Context, Vivien Parmentier, Mike R. Line, Jacob L. Bean, Megan Mansfield, Laura Kreidberg, Roxana Lupu, Channon Visscher, Jean-Michel Desert, Jonathan J. Fortney, Magalie Deleuil, Jacob Arcangeli, Adam P. Showman, Mark S. Marley

Faculty Work Comprehensive List

Context. A new class of exoplanets has emerged: the ultra hot Jupiters, the hottest close-in gas giants. The majority of them have weaker-than-expected spectral features in the 1.1−1.7 μm bandpass probed by HST/WFC3 but stronger spectral features at longer wavelengths probed by Spitzer. This led previous authors to puzzling conclusions about the thermal structures and chemical abundances of these planets.

Aims. We investigate how thermal dissociation, ionization, H− opacity, and clouds shape the thermal structures and spectral properties of ultra hot Jupiters.

Methods. We use the SPARC/MITgcm to model the atmospheres of four ultra hot Jupiters and discuss …

Modulation Of Low-Altitude Ionospheric Upflow By Linear And Nonlinear Atmospheric Gravity Waves, M. R. Burleigh, C. J. Heale, M. D. Zettergren, J. B. Snively

Publications

This study examines how thermospheric motions due to gravity waves (GWs) drive ion upflow in the F region, modulating the topside ionosphere in a way that can contribute to ion outflow. We present incoherent scatter radar data from Sondrestrom, from 31 May 2003 which showed upflow/downflow motions, having a downward phase progression, in the field‐aligned velocity, indicating forcing by a thermospheric GW. The GW‐upflow coupling dynamics are investigated through the use of a coupled atmosphere‐ionosphere model to examine potential impacts on topside ionospheric upflow. Specifically, a sequence of simulations with varying wave amplitude is conducted to determine responses to a …

On The Normalized Frb Luminosity Function, Rui Luo, Kejia Lee, Duncan R. Lorimer, Bing Zhang

Physics & Astronomy Faculty Research

33 fast radio bursts (FRBs) had been detected by 2018 March. Although the sample size is still limited, meaningful statistical studies can already be carried out. The normalized luminosity function places important constraints on the intrinsic power output, sheds light on the origin(s) of FRBs, and can guide future observations. In this paper, we measure the normalized luminosity function of FRBs. Using Bayesian statistics, we can naturally account for a variety of factors such as receiver noise temperature, bandwidth, and source selection criteria. We can also include astronomical systematics, such as host galaxy dispersion measure, FRB local dispersion measure, galaxy …

Dust Production And Depletion In Evolved Planetary Systems, J. Farihi, Ted Von Hippel, Rik Van Lieshout, P.W. Cauley, Erik Dennihy, Et Al.

Publications

The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20 per cent peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disc, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense onto …

Understanding The Death Of Massive Stars Using An Astrophysical Transients Observatory, Peter W. Roming, Eddie Baron, Amanda J. Bayless, Volker Bromm, Peter J. Brown, Michael W. Davis, Anastasia Fialkov, Brian Fleming, Kevin France, Chris L. Fryer, Thomas K. Greathouse, Jed J. Hancock, D. Andrew Howell, Andrew J. Levan, Abraham Loeb, Raffaella Margutti, Mark L. Mcconnell, Paul T. O'Brien, Julian P. Osborne, Daniel A. Perley, Eric M. Schlegel, Rhaana L. C. Starling, Nial R. Tanvir, Mark Tapley, Patrick A. Young, Bing Zhang

Physics & Astronomy Faculty Research

The death of massive stars, manifested as gamma-ray bursts and core-collapse supernovae, critically influence how the universe formed and evolves. Despite their fundamental importance, our understanding of these enigmatic objects is severely limited. We have performed a concept study of an Astrophysical Transient Observatory (ATO) that will rapidly facilitate an expansion of our understanding of these objects. ATO combines a very wide-field X-ray telescope, a near-infrared telescope, a multi-mode ultraviolet instrument, and a rapidly slewing spacecraft to realize two primary goals: (1) characterize the highest-redshift massive stars and their environments, and (2) constrain the poorly understood explosion mechanism of massive …

Parametric Study Of The Rossby Wave Instability In A Two-Dimensional Barotropic Disk. Ii. Nonlinear Calculations, Tomohiro Ono, Takayuki Muto, Kengo Tomida, Zhaohuan Zhu

Physics & Astronomy Faculty Research

Vortices in protoplanetary disks have attracted attention since the discovery of lopsided structures. One of the possible mechanisms for producing vortices is the Rossby wave instability (RWI). In our previous work, we have performed detailed linear stability analyses of the RWI with various initial conditions. In this paper, we perform numerical simulations of the vortex formation by the RWI in two-dimensional barotropic disks using the Athena++ code. As initial conditions, we consider axisymmetric disks with a Gaussian surface density bump of various contrasts and half-widths. Perturbations grow as expected from the linear stability analyses in the linear and weakly nonlinear …

The Distance Of The Dark Matter Deficient Galaxy Ngc 1052–Df2, Pieter Van Dokkum, Shany Danieli, Yotam Cohen, Aaron Romanowsky, Charlie Conroy

Faculty Publications

We recently inferred that the galaxy NGC 1052–DF2 has little or no dark matter and a rich system of unusual globular clusters. We assumed that the galaxy is a satellite of the luminous elliptical galaxy NGC 1052 at ≈20 Mpc, on the basis of its surface brightness fluctuations (SBFs) distance of 19.0 ± 1.7 Mpc, its radial velocity of ≈1800 km s−1, and its projected position. Here we analyze the color–magnitude diagram (CMD) of NGC 1052–DF2, following the suggestion by Trujillo et al. that the tip of the red giant branch (TRGB) can be detected in currently available Hubble Space …

Synchrotron Radiation From Electrons With A Pitch-Angle Distribution, Yuan-Pei Yang, Bing Zhang

Physics & Astronomy Faculty Research

In most astrophysical processes involving synchrotron radiation, the pitch-angle distribution of the electrons is assumed to be isotropic. However, if electrons are accelerated anisotropically, e.g., in a relativistic shock wave with an ordered magnetic field or in magnetic reconnection regions, the electron pitch angles might be anisotropic. In this Letter, we study synchrotron radiation from electrons with a pitch-angle distribution with respect to a large-scale uniform magnetic field. Assuming that the pitch-angle distribution is normal with a scatter of σ p and that the viewing direction is where the pitch-angle direction peaks, we find that for electrons with a Lorentz …

Totality In Carbondale, Grant Haynes

The Hilltop Review

August 21 was one of the high points of 2017. That day a total solar eclipse tracked over much of the continental U.S. An early morning train ride brought me to Carbondale Illinois, the location of the eclipses longest duration. As totality neared clouds obscured this amazing celestial wonder, but they soon parted, and I was able to get a few spectacular photos of the eclipse, this one with the clouds that almost ruined it, is my favorite.

Dark Energy Survey Year 1 Results: Cosmological Constraints From Galaxy Clustering And Weak Lensing, T. M. C. Abbott, F. B. Abdalla, A. Alarcon, J. Aleksic, S. Allam, S. Allen, A. Amara, J. Annis, J. Asorey, S. Avila, D. Bacon, E. Balbinot, M. Banerji, N. Banik, Wayne Barkhouse

Physics Faculty Publications

We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321  deg2 of griz imaging data from the first year of the Dark Energy Survey (DES Y1). We combine three two-point functions: (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. To demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometric-redshift estimation and validation, …

Nitrogen-To-Oxygen Abundance Ratio Variation In Quiescent Galaxies, Renbin Yan

Physics and Astronomy Faculty Publications

For the first time, we establish a gas-phase abundance pattern calibration for quiescent galaxies using optical emission lines. Quiescent galaxies have warm ionized gas showing line ratios similar to low-ionization nuclear emission line regions. The ionization mechanism for the gas is still an unsettled puzzle. Despite the uncertainty in the ionization mechanism, we argue that we can still infer certain gas-phase abundance pattern from first principles. We show that the relative trend in N/O abundance can still be reliably measured based on [N II] λλ6548,6583/[O II] λλ3726,3729 and a direct measurement of the electron temperature. We construct a composite direct …

Spectroscopic Orbits For Late-Type Stars. Ii, Francis C. Fekel, Daryl W. Willmarth, Helmut A. Abt, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

We have determined spectroscopic orbital elements for 13 systems—10 single-lined binaries and three double-lined binaries. For the three binaries with previously published spectroscopic orbits, we have computed improved or comparable elements. While two systems have relatively short periods between 10 and 19 days, the remaining systems have much longer periods ranging from 604 to 9669 days. One of the single-lined systems, HD 142640, shows both short-period and long-period velocity variations and so is triple. For three systems—HD 59380, HD 160933, and HD 161163—we have combined our spectroscopic results with Hipparcos astrometric observations to obtain astrometric orbits. For HD 14802 we …

Suppression Of Dielectronic Recombination Due To Finite Density Effects. Ii. Analytical Refinement And Application To Density-Dependent Ionization Balances And Agn Broad-Line Emission, D. Nikolić, T. W. Gorczyca, K. T. Korista, Marios Chatzikos, Gary J. Ferland, Francisco Guzmán, P. A. M. Van Hoof, R. J. R. Williams, N. R. Badnell

Physics and Astronomy Faculty Publications

We present improved fits to our treatment of suppression of dielectronic recombination at intermediate densities. At low densities, most recombined excited states eventually decay to the ground state, and therefore the total dielectronic recombination rate to all levels is preserved. At intermediate densities, on the other hand, collisions can lead to ionization of higher-lying excited states, thereby suppressing the dielectronic recombination rate. The improved suppression factors presented here, although highly approximate, allow summed recombination rate coefficients to be used to intermediate densities. There have been several technical improvements to our previously presented fits. For H- through B-like ions the activation …

Predictions For The Sky-Averaged Depth Of The 21 Cm Absorption Signal At High Redshift In Cosmologies With And Without Nonbaryonic Cold Dark Matter, Stacy S. Mcgaugh

Faculty Scholarship

We consider the 21 cm absorption signal expected at high redshift in cosmologies with and without nonbaryonic cold dark matter. The expansion of the early Universe decelerates strongly with dark matter, but approximately coasts without it. This results in a different path length across the epochs when absorption is expected, with the consequence that the absorption is predicted to be a factor of ∼2 greater without dark matter than with it. Observation of such a signal would motivate consideration of extended theories of gravity in lieu of dark matter.

Warping A Protoplanetary Disc With A Planet On An Inclined Orbit, Rebecca Nealon, Giovanni Dipierro, Richard Alexander, Rebecca G. Martin, Chris Nixon

Physics & Astronomy Faculty Research

Recent observations of several protoplanetary discs have found evidence of departures from flat, circular motion in the inner regions of the disc. One possible explanation for these observations is a disc warp, which could be induced by a planet on a misaligned orbit. We present three-dimensional numerical simulations of the tidal interaction between a protoplanetary disc and a misaligned planet. For low planet masses, we show that our simulations accurately model the evolution of inclined planet orbit (up to moderate inclinations). For a planet massive enough to carve a gap, the disc is separated into two components and the gas …

A Study Of Hα Line Profile Variations In Β Lyr, Richard Ignace, Sharon K. Gray, Macno A. Magno, Gary D. Henson, Derek Massa

ETSU Faculty Works

We examine over 160 archival Hα spectra from the Ritter Observatory for the interacting binary β Lyr obtained between 1996 and 2000. The emission is characteristically double-peaked, but asymmetric, and with an absorption feature that is persistently blueshifted. Using a set of simplifying assumptions, phase varying emission line profiles are calculated for Hα formed entirely in a Keplerian disk, and separately for the line formed entirely from an off-center bipolar flow. However, a dynamic spectrum of the data indicates that the blueshifted feature is not always present, and the data are even suggestive of a drift of the …

The Sluggs Survey: The Inner Dark Matter Density Slope Of The Massive Elliptical Galaxy Ngc 1407, Asher Wasserman, Aaron Romanowsky, Jean Brodie, Pieter Van Dokkum, Charlie Conroy, Alexa Villaume, Duncan Forbes, Jay Strader, Adebusola Alabi, Sabine Bellstedt

Faculty Publications

We investigate the dark matter density profile of the massive elliptical galaxy, NGC 1407, by constructing spherically symmetric Jeans models of its field star and globular cluster systems. Two major challenges in such models are the degeneracy between the stellar mass and the dark matter halo profiles, and the degeneracy between the orbital anisotropy of the tracer population and the total mass causing the observed motions. We address the first issue by using new measurements of the mass-to-light ratio profile from stellar population constraints that include a radially varying initial mass function. To mitigate the mass–anisotropy degeneracy, we make use …