Astrophysics and Astronomy Commons^™

Impact And Signatures Of Deglaciation On The Cryosphere, Landscape, And Habitability Of Earth And Mars, Nathalie A. Cabrol, Andrew G. Fountain, J. S. Kargel

Geology Faculty Publications and Presentations

Science questions can help bridge Astrobiology and Earth Science disciples around the theme of planetary deglaciation.

Superfluidity In Neutron Stars, Samuel J. Witte

Undergraduate Theses—Unrestricted

Nucleon pairing is studied with specific considerations directed toward the possible influence on neutron star cooling. We present an in-depth analysis of BCS theory using realistic nuclear potentials and consider the impact short-range correlations can have on the gap. Gap calculations are incorporated into neutron star cooling simulations and the significance of the 3P2 −3F2 channel in various hadronic cooling models is closely examined. An analysis of the 1S0 gap in neutron matter suggests short-range correlations can drastically alter the magnitude, density range, and temperature dependence of the gap. While the newly constructed 1S0 gap does not significantly alter the …

An X-Rays Survey Of The Young Stellar Population Of The Lynds 1641 And Iota Orionis Regions, I. Pillitteri, S. J. Wolk, S. T. Megeath, L. Allen, J. Bally, Marc Gagné, R. A. Gutermuth, L. Hartman, G. Micela, P. Myers, J. M. Oliveira, S. Sciortino, F. Walter, L. Rebull, J. Stauffer

Earth & Space Sciences Faculty Publications

We present an XMM-Newton survey of the part of Orion A cloud south of the Orion Nebula. This survey includes the Lynds 1641 (L1641) dark cloud, a region of the Orion A cloud with very few massive stars and hence a relatively low ambient UV flux, and the region around the O9 III star Orionis. In addition to proprietary data, we used archival XMM data of the Orion Nebula Cluster (ONC) to extend our analysis to a major fraction of the Orion A cloud. We have detected 1060 X-ray sources in L1641 and Ori region. About 94% of the sources …

A Biodistribution And Toxicity Study Of Cobalt Dichloride–Nacetyl Cysteine (C4) As An Implantable Mri Marker For Prostate Cancer Treatment, Steven J. Frank, Mary J. Johansen, Karen S. Martirosyan, Mihai Gagea, Carolyn S. Van Pelt

Physics & Astronomy Faculty Publications

Purpose—C4, a cobalt dichloride–N-acetyl cysteine complex, is being developed as a positivesignal magnetic resonance imaging (MRI) marker to localize implanted radioactive seeds in prostate brachytherapy. We evaluated the toxicity and biodistribution of C4 in rats with the goal of simulating systemic effects of potential leakage from C4 MRI markers within the prostate.

Methods—9 μl doses (equivalent to leakage from 120 markers in a human) of control (0.9% sodium chloride), 1% (proposed for clinical use) and 10% C4 solution were injected into the prostates of male Sprague-Dawley rats via laparotomy. Organ toxicity and cobalt disposition in plasma, tissues, feces …

The Spectroscopic Orbits Of Five Solar-Type, Single-Lined Binaries, Francis C. Fekel, Samira Rajabi, Matthew W. Muterspaugh, Michael H. Williamson

Information Systems and Engineering Management Research Publications

We have determined spectroscopic orbits for five single-lined spectroscopic binaries, HD 100167, HD 135991, HD 140667, HD 158222, HD 217924. Their periods range from 60.6 to 2403 days and the eccentricities from 0.20 to 0.84. Our spectral classes for the stars confirm that they are of solar type, F9–G5, and all are dwarfs. Their [Fe/H] abundances, determined spectroscopically, are close to the solar value and on average are 0.12 greater than abundances from a photometric calibration. Four of the five stars are rotating faster than their predicted pseudosynchronous rotational velocities.

Quantum Man, Julian Voss-Andreae

The Transdisciplinary STEAM+ Journal

According to quantum physics, the world is fundamentally quite different than it seems. Drawing inspiration from the underlying nature of reality, former quantum physicist Julian Voss-Andreae created an image of a walking human as a quantum object. Made up of parallel sheets of steel, the sculpture is a metaphor for the counter-intuitive world of quantum physics. Symbolizing the dual nature of matter with the appearance of classical reality on the surface and cloudy quantum behavior underneath, the sculpture seems to consist of solid steel when seen from the front, but dissolves into almost nothing when seen from the side.

Radiative Cooling In Collisionally Ionized And Photoionized Plasmas, Matt Lykins, Gary J. Ferland, Ryan L. Porter, Peter A. M. Van Hoof, R. J. R. Williams, Orly Gnat

Physics and Astronomy Faculty Publications

We discuss recent improvements in the calculation of the radiative cooling in both collisionally ionized and photoionized plasmas. We are extending the spectral simulation code CLOUDY so that as much as possible of the underlying atomic data are taken from external data bases, some created by others and some developed by the CLOUDY team. This paper focuses on recent changes in the treatment of many stages of ionization of iron, and discusses its extensions to other elements. The H- and He-like ions are treated in the isoelectronic approach described previously. Fe II is a special case treated with a large …

Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al.

Publications

Previous works have emphasized the significant influence of the solar wind Alfvén Mach number (MA) on magnetospheric dynamics. Here we report statistical, observational results that pertain to changes in the magnetosheath flow distribution and magnetopause shape as a function of solar wind MA and interplanetary magnetic field (IMF) clock angle orientation. We use all Cluster 1 data in the magnetosheath during the period 2001–2010, using an appropriate spatial superposition procedure, to produce magnetosheath flow distributions as a function of location in themagnetosheath relative to the IMF and other parameters. The results demonstrate that enhanced flows in the magnetosheath are expected …

Quantifying Night Sky Fluctuations: Striving For A Multi-Messenger Astronomy, Rachel K. Nydegger, Shane L. Larson Ph.D.

Browse All Undergraduate research

With LIGO coming back online soon, astronomers are attempting to solve the problems involved with coupling gravitational observations with electromagnetic telescope observations. To do this, my project aims to create all-sky surveys to characterize natural variability to reduce "false-alarm" rates in detections of gravitational emissions.

Effects Of Different Geomagnetic Storm Drivers On The Ring Current: Crcm Results, W D. Cramer, Niescja E. Turner, M C. Fok, N Y. Buzulukova

Physics and Astronomy Faculty Research

The storm-time magnetic disturbance at the Earth's equator, as commonly measured by the Dst index, is induced by currents in the near-Earth magnetosphere. The ring current is generally considered the most important contributor, but other magnetospheric currents have also been found to have significant effects. Of the two main types of solar geomagnetic storm drivers, Coronal Mass Ejections (CMEs) tend to have a much greater impact on Dst than Corotating Interaction Regions (CIRs). Ring current models have been found to underestimate Dst, particularly during storms driven by CIRs. One possible explanation is that the models neglect to handle some aspect …

Andromeda Dwarfs In Light Of Modified Newtonian Dynamics, Stacy S. Mcgaugh

Faculty Scholarship

We compare the recently published velocity dispersions for 17 Andromeda dwarf spheroidals with estimates of the modified Newtonian dynamics predictions, based on the luminosities of these dwarfs, with reasonable stellar mass-to-light values and no dark matter. We find that the two are consistent within the uncertainties. We further predict the velocity dispersions of another 10 dwarfs for which only photometric data are currently available. © 2013. The American Astronomical Society. All rights reserved..

The Spectroscopic Orbit Of The K-Giant Binary Γ Canis Minoris, Francis C. Fekel, Michael H. Williamson, Michael Weber, Klaus G. Strassmeier, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

We have determined an improved orbit for the bright, evolved, double lined binary γ Canis Minoris. The system has an orbital period of 389.31 days and an eccentricity of 0.2586. We have revised the secondary to primary mass ratio to 0.987. The spectral types of the primary and secondary are K4 III and K1: III, respectively, and the components have a V magnitude difference of 2.2. Orbital fits to the Hipparcos astrometry are not definitive, but they suggest an orbital inclination of ∼ 66°, which produces masses of 1.88 and 1.85 M⊙ for the components. A comparison with evolutionary tracks …

Thin-Shell Mixing In Radiative Wind-Shocks And The L-X Similar To L-Bol Scaling Of O-Star X-Rays, S. P. Owocki, J. O. Sundqvist, David H. Cohen, K. G. Gayley

Physics & Astronomy Faculty Works

X-ray satellites since Einstein have empirically established that the X-ray luminosity from single O-stars scales linearly with bolometric luminosity, L-x similar to 10(-7)L(bol). But straightforward forms of the most favoured model, in which X-rays arise from instability-generated shocks embedded in the stellar wind, predict a steeper scaling, either with mass-loss rate L-x similar to(M)over dot similar to L-bol(1.7) if the shocks are radiative or with L-x similar to (M)over dot(2) similar to L-bol(3.4) if they are adiabatic. This paper presents a generalized formalism that bridges these radiative versus adiabatic limits in terms of the ratio of the shock cooling length …

How To Find Killing Vectors, Charles G. Torre

How to... in 10 minutes or less

We show how to compute the Lie algebra of Killing vector fields of a metric in Maple using the commands KillingVectors and LieAlgebraData. A Maple worksheet and a PDF version can be found below.

Prospects For Observing Ultracompact Binaries With Space-Based Gravitational Wave Interferometers And Optical Telescopes., T. B. Littenberg, Shane L. Larson, G. Nelemans Department Of Astrophysics, Radboud University Nijmegen, N. J. Cornish

All Physics Faculty Publications

Space-based gravitational wave interferometers are sensitive to the galactic population of ultra-compact binaries. An important subset of the ultra-compact binary popula- tion are those stars that can be individually resolved by both gravitational wave in- terferometers and electromagnetic telescopes. The aim of this paper is to quantify the multi-messenger potential of space-based interferometers with arm-lengths between 1 and 5 Gm. The Fisher Information Matrix is used to estimate the number of binaries from a model of the Milky Way which are localized on the sky by the gravitational wave detector to within 1 and 10 deg2 and bright enough to …

Faraday Rotation Distributions From Stellar Magnetism In Wind-Blown Bubbles., Richard Ignace, N. Pingel

ETSU Faculty Works

Faraday rotation is a valuable tool for detecting magnetic fields. Here, the technique is considered in relation to wind-blown bubbles. In the context of spherical winds with azimuthal or split monopole stellar magnetic field geometries, we derive maps of the distribution of position angle (P.A.) rotation of linearly polarized radiation across projected bubbles. We show that the morphology of maps for split monopole fields are distinct from those produced by the toroidal field topology; however, the toroidal case is the one most likely to be detectable because of its slower decline in field strength with distance from the star. We …

The Opacity Of Spiral Galaxy Disks : Ix. Dust And Gas Surface Densities., Benne W. Holwerda, R. J. Allen, W. J. G. De Blok, A. Bouchard, R. A. Gonzalez-Lopezlira, P. C. Van Der Kruit, A. Leroy

Faculty and Staff Scholarship

Our aim is to explore the relation between gas, atomic and molecular, and dust in spiral galaxies. Gas surface densities are from atomic hydrogen and CO line emission maps. To estimate the dust content, we use the disk opacity as inferred from the number of distant galaxies identified in twelve HST/WFPC2 fields of ten nearby spiral galaxies. The observed number of distant galaxies is calibrated for source confusion and crowding with artificial galaxy counts and here we verify our results with sub-mm surface brightnesses from archival Herschel-SPIRE data. We find that the opacity of the spiral disk does not correlate …

A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol

Faculty Publications

We provide a pedagogical introduction to numerical linked-cluster expansions (NLCEs). We sketch the algorithm for generic Hamiltonians that only connect nearest-neighbor sites in a finite cluster with open boundary conditions. We then compare results for a specific model, the Heisenberg model, in each order of the NLCE with the ones for the finite cluster calculated directly by means of full exact diagonalization. We discuss how to reduce the computational cost of the NLCE calculations by taking into account symmetries and topologies of the linked clusters. Finally, we generalize the algorithm to the thermodynamic limit, and discuss several numerical resummation techniques …

Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Ii. Physical Conditions, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert

Physics and Astronomy Faculty Publications

We have performed a detailed analysis of the electron temperature and density in the Ring Nebula using the calibrated Hubble Space Telescope WFC3 images described in the preceding paper. The electron temperature (T_e) determined from [NII] and [O III] rises slightly and monotonically toward the central star. The observed equivalent width (EW) in the central region indicates that T_e rises as high as 13,000 K. In contrast, the low EWs in the outer regions are largely due to scattered diffuse Galactic radiation by dust. The images allowed determination of unprecedented small-scale variations in T_e. …

Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. I. Structure And Evolution, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert

Physics and Astronomy Faculty Publications

We have performed a detailed analysis of the Ring Nebula (NGC 6720) using Hubble Space Telescope WFC3 images and derived a new three-dimensional model. Existing high spectral resolution spectra played an important supplementary role in our modeling. It is shown that the Main Ring of the nebula is an ionization-bounded irregular non-symmetric disk with a central cavity and perpendicular extended lobes pointed almost toward the observer. The faint outer halos are determined to be fossil radiation, i.e., radiation from gas ionized in an earlier stage of the nebula when it was not ionization bounded. The narrowband WFC3 filters that isolate …

Mars Up Close: Scott Murchie's Team Of Scientists Helps Uncover The Secrets Of The Red Planet, Tom Nugent

Colby Magazine

Planetary geologist Scott Murchie ’81 leads a team that built and operates the high-tech camera now orbiting Mars and analyzes images used to help select landing sites for the Phoenix lander and the Mars Science Laboratory, scheduled for launch in 2009. Murchie’s work is groundbreaking—literally.

Characterizing Sky Variability For Multi-Messenger Astronomy, Rachel Nydegger

UCUR

Multi-messenger astronomy employs both electromagnetic and gravitational -wave detectors to paint a richer picture of celestial objects, providing more depth and information. The interferometers utilized for gravitational-wave observations receive input from very broad fields of view on the sky, typically a few square degrees. To have simultaneous electromagnetic observations (typically less than one square degree) requires innovative techniques for the telescopes to find the origin of radiation. One idea is to “tile” the view of the interferometer, using multiple telescopes to simultaneously point at different areas of the field to observe the source. One di"culty of this observing paradigm is …

The Interior Structure Constants As An Age Diagnostic For Low-Mass, Pre-Main-Sequence Detached Eclipsing Binary Stars, Gregory A. Feiden, Aaron Dotter

Dartmouth Scholarship

We propose a novel method for determining the ages of low-mass, pre-main-sequence stellar systems using the apsidal motion of low-mass detached eclipsing binaries. The apsidal motion of a binary system with an eccentric orbit provides information regarding the interior structure constants of the individual stars. These constants are related to the normalized stellar interior density distribution and can be extracted from the predictions of stellar evolution models. We demonstrate that low-mass, pre-main-sequence stars undergoing radiative core contraction display rapidly changing interior structure constants (greater than 5% per 10 Myr) that, when combined with observational determinations of the interior structure constants …

Einstein@Home All-Sky Search For Periodic Gravitational Waves In Ligo S5 Data, J. Aasi, J. Abadie, B. P. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Malik Rakhmanov, Volker Quetschke, Joseph D. Romano

Physics & Astronomy Faculty Publications

This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50,1 190]  Hz and with frequency derivative range of ∼[−20,1.1]×10−10  Hz s−1 for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we report upper limits on …

A Magnetic Confinement Versus Rotation Classification Of Massive-Star Magnetospheres, V. Petit, S. P. Owocki, G. A. Wade, David H. Cohen, J. O. Sundqvist, M. Gagné, J. Maíz Apellániz, M. E. Oksala, D. A. Bohlender, T. Rivinius, H. F. Henrichs, E. Alecian, R. H.D. Townsend, A. Ud-Doula

Physics & Astronomy Faculty Works

Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfvén radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) provides a useful organization of both observational signatures and theoretical predictions. We compile the first comprehensive study of inferred and observed values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB stars with Teff ≳ 16 kK. Using these parameters, we locate the stars in the magnetic confinement–rotation diagram, a log–log plot of RK …

A Report On The X-Ray Properties Of The Τ Sco Class Of Stars., Richard Ignace, L. Oskinova, D. Massa

ETSU Faculty Works

An increasing number of OB stars have been shown to possess magnetic fields. Although the sample remains small, it is surprising that the magnetic and X-ray properties of these stars appear to be far less correlated than expected. This contradicts model predictions, which generally indicate that the X-rays from magnetic stars are harder and more luminous than their non-magnetic counterparts. Instead, the X-ray properties of magnetic OB stars are quite diverse. τ Sco is one example where the expectations are better met. This bright main-sequence, early B star has been studied extensively in a variety of wavebands. It has a …

Discovery Of Tev Gamma-Ray Emission From Cta 1 By Veritas, P. T. Reynolds, Et. Al.

Physical Sciences Publications

We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semimajor (semiminor) axis 0fdg30 (0fdg24) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N 0(E/3 TeV)–Γ, with a differential spectral index of Γ = 2.2 ± 0.2stat ± 0.3sys, and normalization …

Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

The acceleration of suprathermal charged particles in the heliosphere under pressure balance conditions including for the first time the radial spatial particle diffusion and convection in the solar wind is investigated. The physical conditions are derived for which the stationary phase space distribution of suprathermal particles approaches the power-law distribution f ∝ p −5,which is often seen in spacecraft observations. For separable source distributions in momentum and position we analytically solve the stationary particle transport equation for a radially constant solar wind speed V0 and a momentum-independent radial spatial diffusion coefficient. The resulting stationary solution at any position within the …

Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen

Aerospace, Physics, and Space Science Faculty Publications

To understand the behavior of cosmic-ray modulation seen by the two Voyager spacecraft in the region near the termination shock (TS) and in the heliosheath at a distance of >100 AU, a realistic magnetohydrodynamic global heliosphere model is incorporated into our cosmic-ray transport code, so that the detailed effects of the heliospheric boundaries and their plasma/magnetic geometry can be revealed. A number of simulations of cosmic-ray modulation performed with this code result in the following conclusions. (1) Diffusive shock acceleration by the TS can significantly affect the level of cosmic-ray flux and, in particular, its radial gradient profile in the …

The Radio And Optical Luminosity Evolution Of Quasars Ii -- The Sdss Sample, Jack Singal, V. Petrosian, L. Stawarz, A. Lawrence

Physics Faculty Publications

We determine the radio and optical luminosity evolutions and the true distribution of the radio-loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining Sloan Digital Sky Survey optical and Faint Images of the Radio Sky at Twenty cm (FIRST) radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift in both wavebands, with somewhat greater radio evolution than optical. …