Observational Constraints On The Degenerate Mass-Radius Relation,
2012
University of Arizona
Observational Constraints On The Degenerate Mass-Radius Relation, J. B. Holberg, Terry D. Oswalt, M. A. Barstow
Publications
The white dwarf mass–radius relationship is fundamental to modern astrophysics. It is central to routine estimation of DA white dwarf masses derived from spectroscopic temperatures and gravities. It is also the basis for observational determinations of the white dwarf initial–final-mass relation. Nevertheless, definitive and detailed observational confirmations of the mass–radius relation (MRR) remain elusive owing to a lack of sufficiently accurate white dwarf masses and radii. Current best estimates of masses and radii allow only broad conclusions about the expected inverse relation between masses and radii in degenerate stars. In this paper, we examine a restricted set of 12 DA …
Ground-State Characterizations Of Systems Predicted To Exhibit L11 Or L13 Crystal Structures,
2012
Brigham Young University
Ground-State Characterizations Of Systems Predicted To Exhibit L11 Or L13 Crystal Structures, Lance J. Nelson, Gus L. W. Hart, Stefano Curtarolo
Faculty Publications
Despite their geometric simplicity, the crystal structures L11 (CuPt) and L13 (CdPt3) do not appear as ground states experimentally, except in Cu-Pt. We investigate the possibility that these phases are ground states in other binary intermetallic systems, but overlooked experimentally. Via the synergy between high-throughput and cluster-expansion computational methods, we conduct a thorough search for systems that may exhibit these phases and calculate order-disorder transition temperatures when they are predicted. High-throughput calculations predict L11 ground states in the systems Ag-Pd, Ag-Pt, Cu-Pt, Pd-Pt, Li-Pd, Li-Pt and L13 ground states in the systems Cd-Pt, Cu-Pt, Pd-Pt, Li-Pd, Li-Pt. Cluster expansions confirm …
The 2010 Very High Energy Gamma-Ray Flare And 10 Years Of Multi-Wavelength Observations Of M 87,
2012
Cork Institute of Technology
The 2010 Very High Energy Gamma-Ray Flare And 10 Years Of Multi-Wavelength Observations Of M 87, P. T. Reynolds, Hess, Magic, Veritas, Et. Al.
Physical Sciences Publications
The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3 – 6) × 109 M ☉) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) γ-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE γ-ray emitter since 2006. The VHE γ-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in …
Numerical Study Of The Thermodynamics Of Clinoatacamite,
2012
Georgetown University
Numerical Study Of The Thermodynamics Of Clinoatacamite, Ehsan Khatami, Joel Helton, Marcos Rigol
Faculty Publications
We study the thermodynamic properties of the clinoatacamite compound, Cu2(OH)3Cl, by considering several approximate models. They include the Heisenberg model on (i) the uniform pyrochlore lattice, (ii) a very anisotropic pyrochlore lattice, and (iii) a kagome lattice weakly coupled to spins that sit on a triangular lattice. We utilize the exact diagonalization of small clusters with periodic boundary conditions and implement a numerical linked-cluster expansion approach for quantum lattice models with reduced symmetries, which allows us to solve model (iii) in the thermodynamic limit. We find a very good agreement between the experimental uniform susceptibility and the numerical results for …
A Generalized Porosity Formalism For Isotropic And Anisotropic Effective Opacity And Its Effects On X-Ray Line Attenuation In Clumped O Star Winds,
2012
Swarthmore College
A Generalized Porosity Formalism For Isotropic And Anisotropic Effective Opacity And Its Effects On X-Ray Line Attenuation In Clumped O Star Winds, J. O. Sundqvist, S. P. Owocki, David H. Cohen, M. A. Leutenegger, R. H.D. Townsend
Physics & Astronomy Faculty Works
We present a generalized formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealized model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of boundfree absorption of …
Bl Lacertae Objects Beyond Redshift 1.3 - Uv-To-Nir Photometry And Photometric Redshift For Fermi/Lat Blazars,
2012
Max-Planck-Instiut für Extraterrestrische Physik, Giessenbachstraß
Bl Lacertae Objects Beyond Redshift 1.3 - Uv-To-Nir Photometry And Photometric Redshift For Fermi/Lat Blazars, A. Rau, P. Schady, J. Greiner, M. Salvato, M. Ajello, E. Bottacini, N. Gehrels, P.M. J. Afonso, J. Elliott, R Filgas, D A. Kann, S Klose, T Krühler, M Nardini, A Nicuesa Guelbenzu, F Olivares E., A Rossi, V Sudilovsky, A C. Updike, Dieter H. Hartmann
Publications
Context.Observations of the γ -ray sky with Fermi led to significant advances towards understanding blazars, the most extreme classof Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whosesample has always suff ered from a severe redshift incompleteness due to the quasi-featureless optical spectra.Aims.Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LACFermi/LAT cataloge.Methods.For 103 Fermi/LAT blazars, photometric redshifts using spectral energy distribution fitting have been obtained. The pho-tometry includes 13 broad-band filters from the far ultraviolet …
Cxom31 J004253.1+411422: The First Ultraluminous X-Ray Transient In M 31,
2012
Department of Physics and Astronomy, Clemson University
Cxom31 J004253.1+411422: The First Ultraluminous X-Ray Transient In M 31, A. Kaur, M. Henze, F. Haberl, W. Pietsch, J. Greiner, A. Rau, Dieter H. Hartmann, G. Sala, M. Hernanz
Publications
Context. We seek clarification of the nature of X-ray sources detected in M 31. Here we focus on CXOM31 J004253.1+411422, the brightness of which suggests that it belongs to the class of ultraluminous X-ray sources. Aims. We determine the X-ray properties of sources detected in the XMM-Newton/Chandra monitoring program. We investigate spectral properties and search for periodic or quasi-periodic oscillations. Methods. A multicomponent model was applied to the spectra obtained from XMM-Newton data to evaluate the relative contributions from thermal and nonthermal emission. The time dependence of this ratio was evaluated over a period of forty days. We simultaneously fit …
An Extreme X-Ray Disk Wind In The Black Hole Candidate Igr J17091-3624,
2012
University of Michigan
An Extreme X-Ray Disk Wind In The Black Hole Candidate Igr J17091-3624, A. L. King, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, T. R. Kallman, D. Maitra, E. M. Cackett, M. P. Rupen
Physics and Astronomy Faculty Research Publications
Chandra spectroscopy of transient stellar-mass black holes in outburst has clearly revealed accretion disk winds in soft, disk-dominated states, in apparent anti-correlation with relativistic jets in low/hard states. These disk winds are observed to be highly ionized, dense, and to have typical velocities of ~1000 km s-1 or less projected along our line of sight. Here, we present an analysis of two Chandra High Energy Transmission Grating spectra of the Galactic black hole candidate IGR J17091-3624 and contemporaneous Expanded Very Large Array (EVLA) radio observations, obtained in 2011. The second Chandra observation reveals an absorption line at 6.91 ± …
Block Preconditioning Of Stiff Implicit Models For Radiative Ionization In The Early Universe,
2012
Southern Methodist University
Block Preconditioning Of Stiff Implicit Models For Radiative Ionization In The Early Universe, Daniel R. Reynolds, Robert Harkness, Geoffrey So, Michael L. Norman
Mathematics Research
No abstract provided.
Deep 1.1mm-Wavelength Imaging Of The Goods-S Field By Aztec/Aste - Ii. Redshift Distribution And Nature Of The Submillimetre Galaxy Population,
2012
University of Massachusetts Amherst
Deep 1.1mm-Wavelength Imaging Of The Goods-S Field By Aztec/Aste - Ii. Redshift Distribution And Nature Of The Submillimetre Galaxy Population, Min S. Yun, K. S. Scott, Yicheng Guo, I. Aretxaga, M. Giavalisco, J. E. Austermann, P. Capak, Yuxi Chen, H. Ezawa, B. Hatsukade, D. H. Hughes, D. Iono, S. Johnson, R. Kawabe, K. Kohno, James D. Lowenthal, N. Miller, G. Morrison, T. Oshima, T. A. Perera, M. Salvato, J. Silverman, Y. Tamura, C. C. Williams, G. W. Wilson
Astronomy: Faculty Publications
We report the results of the counterpart identification and a detailed analysis of the physical properties of the 48 sources discovered in our deep 1.1-mm wavelength imaging survey of the Great Observatories Origins Deep Survey-South (GOODS-S) field using the AzTEC instrument on the Atacama Submillimeter Telescope Experiment. One or more robust or tentative counterpart candidate is found for 27 and 14 AzTEC sources, respectively, by employing deep radio continuum, Spitzer/Multiband Imaging Photometer for Spitzer and Infrared Array Camera, and Large APEX Bolometer Camera 870μm data. Five of the sources (10 per cent) have two robust counterparts each, supporting the idea …
Fragile Binary Candidates In The Sdss Dr8 Spectroscopic Archive,
2012
Florida Institute of Technology
Fragile Binary Candidates In The Sdss Dr8 Spectroscopic Archive, J K. Zhao, Terry D. Oswalt, G Zhao
Aerospace, Physics, and Space Science Faculty Publications
We present a catalog of 80 very wide fragile binary candidates (projected separations >10,000 AU) from the Sloan Digital Sky Survey Data Release Eight spectral archive. The pairs were selected based on proper motion, radial velocity, metallicity, and photometric parallax criteria. The angular separations of these pairs range from 3" to 250 ". The peak in the metallicity distribution of these pairs is about −0.5 dex of solar metallicity. Space motions and reduced proper motion diagrams indicate that all these pairs are members of the disk. The chromospheric activity index SHK of each component in 38 binary candidates having spectra …
Star Formation In Self-Gravitating Disks In Active Galactic Nuclei. Ii. Episodic Formation Of Broad-Line Regions,
2012
Chinese Academy of Sciences, China
Star Formation In Self-Gravitating Disks In Active Galactic Nuclei. Ii. Episodic Formation Of Broad-Line Regions, Jian-Min Wang, Pu Du, Jack A. Baldwin, Jun-Qiang Ge, Chen Hu, Gary J. Ferland
Physics and Astronomy Faculty Publications
This is the second in a series of papers discussing the process and effects of star formation in the self-gravitating disk around the supermassive black holes in active galactic nuclei (AGNs). We have previously suggested that warm skins are formed above the star-forming (SF) disk through the diffusion of warm gas driven by supernova explosions. Here we study the evolution of the warm skins when they are exposed to the powerful radiation from the inner part of the accretion disk. The skins initially are heated to the Compton temperature, forming a Compton atmosphere (CAS) whose subsequent evolution is divided into …
The Evaluation Of Erk1 Dimerization Models Using Fluorescence Correlation Spectroscopy And The Development Of Analysis Algorithms For Single-Molecule Super Resolution,
2012
University of New Mexico
The Evaluation Of Erk1 Dimerization Models Using Fluorescence Correlation Spectroscopy And The Development Of Analysis Algorithms For Single-Molecule Super Resolution, Fang Huang
Physics & Astronomy ETDs
In this dissertation, we describe three advancements in the area of fluorescence spectroscopy and microscopy. First, we have implemented Fluorescence Correlation Spectroscopy on a home-built confocal microscope. We proposed F/N analysis which stands for the ratio between average intensity and average number of moving objects in FCS as a method to detect dimerization of fluorescently tagged proteins diffusing in three dimensions. We used the technique to evaluate the dimerization hypothesis of ERK1 protein during nucleus translocation and it shows that ERK1 nucleus translocation is dimerization independent. Second, we have developed a multi-emitter analysis algorithm for single-molecule super resolution techniques that …
3-D Mesoscale Mhd Simulations Of Magnetospheric Cusp-Like Configurations: Cusp Diamagnetic Cavities And Boundary Structure,
2012
University of Alaska, Fairbanks
3-D Mesoscale Mhd Simulations Of Magnetospheric Cusp-Like Configurations: Cusp Diamagnetic Cavities And Boundary Structure, E. Adamson, A. Otto, K. Nykyri
Publications
We present results from mesoscale simulations of the magnetospheric cusp region for both strongly northward and strongly southward interplanetary magnetic field (IMF). Simulation results indicate an extended region of depressed magnetic field and strongly enhanced plasma B which exhibits a strong dependence on IMF orientation. These structures correspond to the Cusp Diamagnetic Cavities (CDC’s). The typical features of these CDC’s are generally well reproduced by the simulation. The inner boundaries between the CDC and the magnetosphere are gradual transitions which form a clear funnel shape, regardless of IMF orientation. The outer CDC/magnetosheath boundary exhibits a clear indentation in both the …
The Initial–Final Mass Relation Among White Dwarfs In Wide Binaries,
2012
Florida Institute of Technology
The Initial–Final Mass Relation Among White Dwarfs In Wide Binaries, J. K. Zhao, T. D. Oswalt, L. A. Willson, Q. Wang, G. Zhao
Publications
We present the initial–final mass relation derived from 10 white dwarfs in wide binaries that consist of a main-sequence star and a white dwarf. The temperature and gravity of each white dwarf were measured by fitting theoretical model atmospheres to the observed spectrum using a χ2 fitting algorithm. The cooling time and mass were obtained using theoretical cooling tracks. The total age of each binary was estimated from the chromospheric activity of its main-sequence component to an uncertainty of about 0.17 dex in log t. The difference between the total age and white dwarf cooling time is taken …
Stable Ordered Structures Of Binary Technetium Alloys From First Principles,
2012
Brigham Young University
Stable Ordered Structures Of Binary Technetium Alloys From First Principles, Gus L. W. Hart, Ohad Levy, Junkai Xue, Shidong Wang, Stefano Curtarolo
Faculty Publications
Technetium, element 43, is the only radioactive transition metal. It occurs naturally on earth in only trace amounts. Experimental investigation of its possible compounds is thus inherently difficult and limited. Half of the Tc-transition-metal systems (14 out of 28) are reported to be phase separating or lack experimental data. Using high-throughput first-principles calculations, we present a comprehensive investigation of the binary alloys of technetium with the transition metals. The calculations predict stable, ordered structures in nine of these 14 binary systems. They also predict additional compounds in all nine known compound-forming systems and in two of the five systems reported …
Rovibrationally Resolved Direct Photodissociation Through The Lyman And Werner Transitions Of H2 For Fuv/X-Ray-Irradiated Environments,
2012
University of Georgia
Rovibrationally Resolved Direct Photodissociation Through The Lyman And Werner Transitions Of H2 For Fuv/X-Ray-Irradiated Environments, C. D. Gay, N. P. Abel, R. L. Porter, P. C. Stancil, Gary J. Ferland, G. Shaw, P. A. M. Vanhoof, R. J. R. Williams
Physics and Astronomy Faculty Publications
Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H2 through the B1Σ+u ← X1Σ+g (Lyman) and C1Πu ← X1Σ+g (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 Å to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and …
Stellar Populations And The Star Formation Histories Of Lsb Galaxies - Part I: Optical And Hα Imaging,
2012
Case Western Reserve University
Stellar Populations And The Star Formation Histories Of Lsb Galaxies - Part I: Optical And Hα Imaging, Stacy S. Mcgaugh
Faculty Scholarship
This paper presents optical and H imaging for a large sample of LSB galaxies selected from the PSS-II catalogs (Schombert et al., 1992). As noted in previous work, LSB galaxies span a range of luminosities (-10>MV>-20) and sizes (0.3kpc
The Baryonic Tully-Fisher Relation Of Gas-Rich Galaxies As A Test Of Λcdm And Mond,
2012
Case Western Reserve University
The Baryonic Tully-Fisher Relation Of Gas-Rich Galaxies As A Test Of Λcdm And Mond, Stacy S. Mcgaugh
Faculty Scholarship
The baryonic Tully-Fisher relation (BTFR) is an empirical relation between baryonic mass and rotation velocity in disk galaxies. It provides tests of galaxy formation models in ΛCDM and of alternative theories like modified Newtonian dynamics (MOND). Observations of gas-rich galaxies provide a measure of the slope and normalization of the BTFR that is more accurate (if less precise) than that provided by star-dominated spirals, as their masses are insensitive to the details of stellar population modeling. Recent independent data for such galaxies are consistent with M b = AV 4f with A = 47 6 M km -4 s 4. …
Observability Of Pulsar Beam Bending By The Sgr A* Black Hole,
2012
University of Texas Rio Grande Valley
Observability Of Pulsar Beam Bending By The Sgr A* Black Hole, K. Stovall, Teviet Creighton, Richard H. Price, Fredrick A. Jenet
Physics & Astronomy Faculty Publications
According to some models, there may be a significant population of radio pulsars in the Galactic center. In principle, a beam from one of these pulsars could pass close to the supermassive black hole (SMBH) at the center, be deflected, and be detected by Earth telescopes. Such a configuration would be an unprecedented probe of the properties of spacetime in the moderate- to strong-field regime of the SMBH. We present here background on the problem, and approximations for the probability of detection of such beams. We conclude that detection is marginally possible with current telescopes, but that telescopes that will …
