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Astrophysics and Astronomy

2009

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Articles 1 - 30 of 358

Full-Text Articles in Physical Sciences and Mathematics

Retired A Stars And Their Companions. Iii. Comparing The Mass–Period Distributions Of Planets Around A-Type Stars And Sun-Like Stars, Brendan P. Bowler, John Asher Johnson, Geoffrey W. Marcy, Gregory W. Henry, Kathryn M. G. Peek, Debra A. Fischer, Kelsey I. Clubb, Michael C. Liu, Sabine Reffert, Christian Schwab, Thomas B. Lowe Dec 2009

Retired A Stars And Their Companions. Iii. Comparing The Mass–Period Distributions Of Planets Around A-Type Stars And Sun-Like Stars, Brendan P. Bowler, John Asher Johnson, Geoffrey W. Marcy, Gregory W. Henry, Kathryn M. G. Peek, Debra A. Fischer, Kelsey I. Clubb, Michael C. Liu, Sabine Reffert, Christian Schwab, Thomas B. Lowe

Information Systems and Engineering Management Research Publications

We present an analysis of ∼5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 ≲ M*/M☉≲ 2.0) with the goal of measuring the occurrence rate of Jovian planets around (evolved) A-type stars and comparing the distributions of their orbital and physical characteristics to those of planets around Sun-like stars. We provide updated orbital solutions incorporating new radial velocity measurements for five known planet-hosting stars in our sample; uncertainties in the fitted parameters are assessed using a Markov-Chain Monte Carlo method. The frequency of Jovian planets interior to 3 AU is 26+9−8%, …

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Equalization Of Loudspeakers And Enclosed Sound Fields, Xi Chen Dec 2009

Equalization Of Loudspeakers And Enclosed Sound Fields, Xi Chen

Theses and Dissertations

Equalization of loudspeakers and enclosed sound fields has been a topic of considerable interest for decades. Confusion has often arisen among audio professionals regarding the feasibility of simultaneously equalizing a loudspeaker and the enclosed field (i.e., the “room”) it excites. Because of frustrations encountered in such efforts, some have advocated abandoning simultaneous equalization altogether. This dissertation discusses the drawbacks of this approach as well as traditional in situ equalization methods. It demonstrates that many problems with traditional equalization stem from the use of measured acoustic pressure at a discrete point in a sound field as the system output. The dissertation …

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A Super-Earth And Two Neptunes Orbiting The Nearby Sun-Like Star 61 Virginis, Steve Vogt, Robert A. Wittenmyer, R. Paul Butler, Simon O'Toole, Gregory W. Henry, Eugenio J. Rivera, Stefano Meschiari, Gregory Laughlin, Chris G. Tinney, Hugh R. A. Jones, Jeremy Bailey, Brad D. Carter, Konstantin Batygin Dec 2009

A Super-Earth And Two Neptunes Orbiting The Nearby Sun-Like Star 61 Virginis, Steve Vogt, Robert A. Wittenmyer, R. Paul Butler, Simon O'Toole, Gregory W. Henry, Eugenio J. Rivera, Stefano Meschiari, Gregory Laughlin, Chris G. Tinney, Hugh R. A. Jones, Jeremy Bailey, Brad D. Carter, Konstantin Batygin

Information Systems and Engineering Management Research Publications

We present precision radial velocity data that reveal a multiple exoplanet system orbiting the bright nearby G5V star 61 Virginis. Our 4.6 years of combined Keck/HIRES and Anglo-Australian Telescope precision radial velocities indicate the hitherto unknown presence of at least three planets orbiting this well-studied star. These planets are all on low-eccentricity orbits with periods of 4.2, 38.0, and 124.0 days, and projected masses (Msin i) of 5.1, 18.2, and 24.0 M⊕, respectively. Test integrations of systems consistent with the radial velocity data suggest that the configuration is dynamically stable. Depending on the effectiveness of tidal dissipation within the inner …

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A Super-Earth Orbiting The Nearby Sun-Like Star Hd 1461, Eugenio J. Rivera, R. Paul Butler, Steve Vogt, Gregory Laughlin, Gregory W. Henry, Stefano Meschiari Dec 2009

A Super-Earth Orbiting The Nearby Sun-Like Star Hd 1461, Eugenio J. Rivera, R. Paul Butler, Steve Vogt, Gregory Laughlin, Gregory W. Henry, Stefano Meschiari

Information Systems and Engineering Management Research Publications

We present precision radial velocity (RV) data that reveal a Super-Earth mass planet and two probable additional planets orbiting the bright nearby G0V star HD 1461. Our 12.8 years of Keck High Resolution Echelle Spectrometer precision RVs indicate the presence of a 7.4 M⊕ planet on a 5.77 day orbit. The data also suggest, but cannot yet confirm, the presence of outer planets on low-eccentricity orbits with periods of 446.1 and 5017 days, and projected masses (Msin i) of 27.9 and 87.1 M⊕, respectively. Test integrations of systems consistent with the RV data suggest that the configuration is dynamically stable. …

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Discovery Of Very High Energy Gamma Rays From Pks 1424+240 And Multiwavelength Constraints On Its Redshift, P. T. Reynolds, Et Al Dec 2009

Discovery Of Very High Energy Gamma Rays From Pks 1424+240 And Multiwavelength Constraints On Its Redshift, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the first detection of very high energy83Gamma-ray emission above 100 GeV. (VHE) gamma-ray emission above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140 GeV measured by VERITAS is well described by a power law with a photon index of 3.8 ± 0.5stat ± 0.3syst and a flux normalization at 200 GeV of (5.1 ± 0.9stat ± 0.5syst) × 10–11 TeV–1 cm–2 s–1, where stat and syst denote the statistical and systematical uncertainties, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (from …

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Carbon Coated Tellurium For Optical Data Storage, Jonathan D. Abbott Dec 2009

Carbon Coated Tellurium For Optical Data Storage, Jonathan D. Abbott

Theses and Dissertations

A highly durable optical disk has been developed for data archiving. This optical disk uses tellurium as the write layer and carbon as a dielectric and oxidation prevention layer. The sandwich style CTeC film was deposited on polycarbonate and silicon substrates by plasma sputtering. These films were then characterized with SEM, TEM, EELS, ellipsometry, ToF-SIMS, etc, and were tested for writability and longevity. Results show the films were uniform in physical structure, are stable, and able to form permanent pits. Data was written to a disk and successfully read back in a commercial DVD drive.

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The Acs Survey Of Galactic Globular Clusters. Ix. Horizontal Branch Morphology And The Second Parameter Phenomenon, Aaron Dotter, Ata Sarajedini, Jay Anderson, Antonio Aparicio, Luigi R. Bedin, Brian Chaboyer Dec 2009

The Acs Survey Of Galactic Globular Clusters. Ix. Horizontal Branch Morphology And The Second Parameter Phenomenon, Aaron Dotter, Ata Sarajedini, Jay Anderson, Antonio Aparicio, Luigi R. Bedin, Brian Chaboyer

Dartmouth Scholarship

The horizontal branch (HB) morphology of globular clusters (GCs) is most strongly influenced by metallicity. The second parameter phenomenon, first described in the 1960s, acknowledges that metallicity alone is not enough to describe the HB morphology of all GCs. In particular, astronomers noticed that the outer Galactic halo contains GCs with redder HBs at a given metallicity than are found inside the solar circle. Thus, at least a second parameter was required to characterize HB morphology. While the term "second parameter" has since come to be used in a broader context, its identity with respect to the original problem has …

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Measured Optical Constants Of Copper From 10 Nm To 35 Nm, David D. Allred, Nicole Brimhall, Nicholas Herrick, Justin Peatross, R. Steven Turley, Michael Ware Dec 2009

Measured Optical Constants Of Copper From 10 Nm To 35 Nm, David D. Allred, Nicole Brimhall, Nicholas Herrick, Justin Peatross, R. Steven Turley, Michael Ware

Faculty Publications

We use laser high-order harmonics and a polarization-ratioreflectance technique to determine the optical constants of copper and oxidized copper in the wavelength range 10-35 nm. This measurement resolves previously conflicting data sets, where disagreement on optical constants of copper in the extreme ultraviolet most likely arises from inadvertent oxidation of samples before measurement.

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Absolute Dimensions Of The G7+K7 Eclipsing Binary Star Im Virginis: Discrepancies With Stellar Evolution Models, Juan Carlos Morales, Guillermo Torres, Laurence A. Marschall, William C. Brehm Dec 2009

Absolute Dimensions Of The G7+K7 Eclipsing Binary Star Im Virginis: Discrepancies With Stellar Evolution Models, Juan Carlos Morales, Guillermo Torres, Laurence A. Marschall, William C. Brehm

Physics and Astronomy Faculty Publications

We report extensive spectroscopic and differential photometric BVRI observations of the active, detached, 1.309-day double-lined eclipsing binary IMVir, composed of a G7-type primary and a K7 secondary.With these observations, we derive accurate absolute masses and radii of M1 = 0.981 + 0.012M, M2 = 0.6644 + 0.0048M, R1 = 1.061 + 0.016R, and R2 = 0.681 + 0.013R for the primary and secondary, with relative errors under 2%. The effective temperatures are 5570 + 100 K and 4250 + 130 K, respectively. The significant difference in mass makes this a favorable case for comparison with stellar evolution theory.We find that …

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Nanoscopic Investigation Of Surface Morphology Of Neural Growth Cones And Indium Containing Group-Iii Nitrides, Göksel Durkaya Dec 2009

Nanoscopic Investigation Of Surface Morphology Of Neural Growth Cones And Indium Containing Group-Iii Nitrides, Göksel Durkaya

Physics and Astronomy Dissertations

This research focuses on the nanoscopic investigation of the three-dimensional surface morphology of the neural growth cones from the snail Helisoma trivolvis, and InN and InGaN semiconductor material systems using Atomic Force Microscopy (AFM). In the analysis of the growth cones, the results obtained from AFM experiments have been used to construct a 3D architecture model for filopodia. The filopodia from B5 and B19 neurons have exhibited different tapering mechanisms. The volumetric analysis has been used to estimate free Ca2+ concentration in the filopodium. The Phase Contrast Microscopy (PCM) images of the growth cones have been corrected to thickness provided …

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Analysis Of Gan/Alxga1?Xn Heterojunction Dual-Band Photodetectors Using Capacitance Profiling Techniques, Laura E. Byrum Dec 2009

Analysis Of Gan/Alxga1?Xn Heterojunction Dual-Band Photodetectors Using Capacitance Profiling Techniques, Laura E. Byrum

Physics and Astronomy Theses

Capacitance-voltage-frequency measurements on n+-GaN/AlxGa1−xN UV/IR dual-band detectors are reported. The presence of shallow Si-donor, deep Si-donor, and C-donor/N-vacancy defect states were found to significantly alter the electrical characteristics of the detectors. The barrier Al fraction was found to change the position of the interface defect states relative to the Fermi level. The sample with Al fraction of 0.1 shows a distinct capacitance-step and hysteresis, which is attributed to C-donor/N-vacancy electron trap states located above the Fermi level (200 meV) at the heterointerface; whereas, the sample with Al fraction of 0.026 shows negative capacitance and dispersion, indicating C-donor/N-vacancy and deep Si-donor …

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The Greenhouse Effect: Common Misconceptions And Effective Instruction, Trevor W. Strickland Dec 2009

The Greenhouse Effect: Common Misconceptions And Effective Instruction, Trevor W. Strickland

Physics

This study is an extension of the research of Dr. John Keller. It attempts to identify common student misconceptions regarding the greenhouse effect and investigate instructional methods of teaching the greenhouse effect. Dr. Keller developed a test, known as the Greenhouse Effect Concept Inventory (GECI), designed to measure a student’s understanding of the greenhouse effect. A central goal of this project is to investigate the effectiveness of this concept inventory at measuring differences in student knowledge of the greenhouse effect. In addition to the Cal Poly student population that participated in this research, we will be looking at the population …

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On Neutral Absorption And Spectral Evolution In X-Ray Binaries, J. M. Miller, E. M. Cackett, R. C. Reis Dec 2009

On Neutral Absorption And Spectral Evolution In X-Ray Binaries, J. M. Miller, E. M. Cackett, R. C. Reis

Physics and Astronomy Faculty Research Publications

Current X-ray observatories make it possible to follow the evolution of transient and variable X-ray binaries across a broad range in luminosity and source behavior. In such studies, it can be unclear whether evolution in the low-energy portion of the spectrum should be attributed to evolution in the source, or instead to evolution in neutral photoelectric absorption. Dispersive spectrometers make it possible to address this problem. We have analyzed a small but diverse set of X-ray binaries observed with the Chandra High Energy Transmission Grating Spectrometer across a range in luminosity and different spectral states. The column density in individual …

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Observations Of Very High Energy Gamma-Ray Emission From Supernova Remnants With Veritas, Mark Theiling Dec 2009

Observations Of Very High Energy Gamma-Ray Emission From Supernova Remnants With Veritas, Mark Theiling

All Dissertations

The nature and source of cosmic rays has been at the core of particle astrophysics since their discovery almost a century ago. The cosmic ray spectrum is best described by a broken power law, and can be better understood as three distinct parts. Theory holds that cosmic rays up to ∼1015 eV – those below the “knee” or steepening in the spectrum – are produced in the shocks of supernova remnants. Direct detection of cosmic rays produced in supernova remnant shocks is impossible, however, as cosmic rays below ∼1018 eV are deflected by the Galactic magnetic field and cannot be …

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Branchings And Time Evolution Of Reaction Networks, Changyuan Wang Dec 2009

Branchings And Time Evolution Of Reaction Networks, Changyuan Wang

All Dissertations

In this thesis I analyze flows in reaction networks in terms of branchings
in a digraph. If the coupled differential equations governing the rate
of change of probabilities X of a state or species are finite-differenced in time, a matrix equation (I + Adt)X(t+dt) = X(t) results, where X(t) is a vector giving the probabilities at time t and X(t+dt) is a vector giving the probabilities at time t + dt. I demonstrate that the matrix (I + Adt) may be written as the product of an incidence matrix and a weight matrix for a directed graph (digraph) representing the …

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Timing Stability Of Millisecond Pulsars And Prospects For Gravitational-Wave Detection, J. P.W. Verbiest, M. Bailes, W. A. Coles, G. B. Hobbs, W. Van Straten, D. J. Champion, F. A. Jenet, R. N. Manchester, N. D.R. Bhat, J. M. Sarkissian, D. Yardley, S. Burke-Spolaor, A. W. Hotan, X. P. You Dec 2009

Timing Stability Of Millisecond Pulsars And Prospects For Gravitational-Wave Detection, J. P.W. Verbiest, M. Bailes, W. A. Coles, G. B. Hobbs, W. Van Straten, D. J. Champion, F. A. Jenet, R. N. Manchester, N. D.R. Bhat, J. M. Sarkissian, D. Yardley, S. Burke-Spolaor, A. W. Hotan, X. P. You

Physics and Astronomy Faculty Publications and Presentations

The analysis of high-precision timing observations of an array of ∼20 millisecond pulsars (a so-called 'timing array') may ultimately result in the detection of a stochastic gravitational-wave background. The feasibility of such a detection and the required duration of this type of experiment are determined by the achievable rms of the timing residuals and the timing stability of the pulsars involved. We present results of the first long-term, high-precision timing campaign on a large sample of millisecond pulsars used in gravitational-wave detection projects. We show that the timing residuals of most pulsars in our sample do not contain significant low-frequency …

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The White Dwarfs Within 20 Parsecs Of The Sun: Kinematics And Statistics, Edward M. Sion, Jay B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic Dec 2009

The White Dwarfs Within 20 Parsecs Of The Sun: Kinematics And Statistics, Edward M. Sion, Jay B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic

Aerospace, Physics, and Space Science Faculty Publications

We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20 pc of the Sun. We find no convincing evidence of halo white dwarfs in the total 20 pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20 pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20 pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The …

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A Measurement Of Coherent Neutral Pion Production In Neutrino Neutral Current Interactions In The Nomad Experiment, C. T. Kullenberg, S. R. Mishra, M. B. Seaton, J. J. Kim, X. C. Tian, A. M. Scott, M. Kirsanov, Roberto Petti, S. Alekhin, P. Astier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, M. Banner, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, Et. Al. Nov 2009

A Measurement Of Coherent Neutral Pion Production In Neutrino Neutral Current Interactions In The Nomad Experiment, C. T. Kullenberg, S. R. Mishra, M. B. Seaton, J. J. Kim, X. C. Tian, A. M. Scott, M. Kirsanov, Roberto Petti, S. Alekhin, P. Astier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, M. Banner, G. Bassompierre, K. Benslama, N. Besson, I. Bird, B. Blumenfeld, F. Bobisut, Et. Al.

Faculty Publications

We present a study of exclusive neutral pion production in neutrino–nucleus Neutral Current interactions using data from the NOMAD experiment at the CERN SPS. The data correspond to 1.44 X 106 muon-neutrino Charged Current interactions in the energy range 2.5 ≤ E v & ≤ 300GeV. Neutrino events with only one visible π0 in the final state are expected to result from two Neutral Current processes: coherent π0 production, v + A

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The Spectroscopic Orbit Of Sao 167450, Visual Companion Of Aa Ceti, Francis C. Fekel, Daryl W. Willmarth Nov 2009

The Spectroscopic Orbit Of Sao 167450, Visual Companion Of Aa Ceti, Francis C. Fekel, Daryl W. Willmarth

Information Systems and Engineering Management Research Publications

We have determined a spectroscopic orbit for SAO 167450, which is the visual secondary of the W UMa-type eclipsing binary AA Cet, and so the system is quadruple. Radial velocities from the coudé feed and 4 m telescopes at Kitt Peak National Observatory produce an orbit with a period of 25.68 days and an eccentricity of 0.50. We classify both the primary and secondary as G0 subgiant/dwarf stars and find that they are somewhat metal rich relative to the Sun. The high lithium abundances of both components argue that the stars are less than 1 Gyr old. If the components …

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Discovery Of A Magnetic Field In The O9 Sub-Giant Star Hd 57682 By The Mimes Collaboration, J. H. Grunhut, G. A. Wade, W. L.F. Marcolino, V. Petit, H. F. Henrichs, David H. Cohen, E. Alecian, D. A. Bohlender, J.-C. Bouret, O. Kochukhov, C. Neiner, N. St. Louis, R. H.D. Townsend Nov 2009

Discovery Of A Magnetic Field In The O9 Sub-Giant Star Hd 57682 By The Mimes Collaboration, J. H. Grunhut, G. A. Wade, W. L.F. Marcolino, V. Petit, H. F. Henrichs, David H. Cohen, E. Alecian, D. A. Bohlender, J.-C. Bouret, O. Kochukhov, C. Neiner, N. St. Louis, R. H.D. Townsend

Physics & Astronomy Faculty Works

We report the detection of a strong, organized magnetic field in the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the 3.6-m Canada-France-Hawaii Telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Programme. From the fitting of our spectra using non-local thermodynamic equilibrium model atmospheres, we determined that HD 57682 is a 17(-9)(+19)M(circle dot) star with a radius of 7.0(-1.8)(+2.4)R(circle dot) and a relatively low mass-loss rate of 1.4(-0.95)(+3.1) x 10(-9) M(circle dot) yr(-1). The photospheric absorption lines are narrow, and we use the Fourier transform technique to infer v sin i = 15 …

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Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Collisionless Models Revisited, Jorge Villa-Vargas, Isaac Shlosman, Clayton Heller Nov 2009

Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Collisionless Models Revisited, Jorge Villa-Vargas, Isaac Shlosman, Clayton Heller

Department of Physics and Astronomy Faculty Publications

We construct and evolve three one-parameter families and one two-parameter family of steady-state models of stellar disks embedded in live dark matter (DM) halos in order to study the dynamical and secular phases of bar evolution. These models are tested against those published in the literature in order to extend them and to include the gaseous component in the follow-up paper. Specifically, we are interested in the angular momentum, J, redistribution in the disk-halo system during these two evolutionary phases without distinguishing between the resonant and non-resonant effects. We confirm the previous results and quantify for the first time …

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Search For Gravitational-Wave Bursts In The First Year Of The Fifth Ligo Science Run, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales Nov 2009

Search For Gravitational-Wave Bursts In The First Year Of The Fifth Ligo Science Run, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales

Faculty Publications

We present the results obtained from an all-sky search for gravitational-wave (GW) bursts in the 64-2000 Hz frequency range in data collected by the LIGO detectors during the first year (November 2005-November 2006) of their fifth science run. The total analyzed live time was 268.6 days. Multiple hierarchical data analysis methods were invoked in this search. The overall sensitivity expressed in terms of the root-sum-square (rss) strain amplitude hrss for gravitational-wave bursts with various morphologies was in the range of 6×10-22Hz-1/2 to a few×10-21Hz-1/2. No GW signals were observed and a frequentist upper limit of 3.75 events per year on …

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Search For High Frequency Gravitational-Wave Bursts In The First Calendar Tear Of Ligo's Fifth Science Run, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales Nov 2009

Search For High Frequency Gravitational-Wave Bursts In The First Calendar Tear Of Ligo's Fifth Science Run, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, C. Barker, D. Barker, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, B. Behnke, M. Benacquista, Tiffany Z. Summerscales

Faculty Publications

We present an all-sky search for gravitational waves in the frequency range 1 to 6 kHz during the first calendar year of LIGO's fifth science run. This is the first untriggered LIGO burst analysis to be conducted above 3 kHz. We discuss the unique properties of interferometric data in this regime. 161.3 days of triple-coincident data were analyzed. No gravitational events above threshold were observed and a frequentist upper limit of 5.4year-1 on the rate of strong gravitational-wave bursts was placed at a 90% confidence level. Implications for specific theoretical models of gravitational-wave emission are also discussed. © 2009 The …

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Comparison Of Alpha-Element-Enhanced Simple Stellar Population Models With Milky Way Globular Clusters, Hyun Chul Lee, Guy Worthey, Aaron Dotter Nov 2009

Comparison Of Alpha-Element-Enhanced Simple Stellar Population Models With Milky Way Globular Clusters, Hyun Chul Lee, Guy Worthey, Aaron Dotter

Physics and Astronomy Faculty Publications and Presentations

We present simple stellar population (SSP) models with scaled-solar and α-element-enhanced abundances. The SSP models are based on the Dartmouth Stellar Evolution Database, our library of synthetic stellar spectra, and a detailed systematic variation of horizontal-branch (HB) morphology with age and metallicity. In order to test the relative importance of a variety of SSP model ingredients, we compare our SSP models with integrated spectra of 41 Milky Way globular clusters (MWGCs) from Schiavon etal. Using the Mg b and Ca4227 indices, we confirm that Mg and Ca are enhanced by about +0.4 and +0.2dex, respectively, in agreement with results from …

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Dusty Structure Around Type-I Active Galactic Nuclei: Clumpy Torus Narrow-Line Region And Near-Nucleus Hot Dust, Rivay Mor, Hagai Netzer, Moshe Elitzur Nov 2009

Dusty Structure Around Type-I Active Galactic Nuclei: Clumpy Torus Narrow-Line Region And Near-Nucleus Hot Dust, Rivay Mor, Hagai Netzer, Moshe Elitzur

Physics and Astronomy Faculty Publications

We fitted Spitzer/IRS ~ 2-35 μm spectra of 26 luminous quasi-stellar objects in an attempt to define the main emission components. Our model has three major components: a clumpy torus, dusty narrow-line region (NLR) clouds, and a blackbody-like dust. The models utilize the clumpy torus of Nenkova et al. and are the first to allow its consistent check in type-I active galactic nuclei (AGNs). Single torus models and combined torus-NLR models fail to fit the spectra of most sources, but three-component models adequately fit the spectra of all sources. We present torus inclination, cloud distribution, covering factor, and …

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Measuring The Spin Of Grs 1915+105 With Relativistic Disk Reflection, J. L. Blum, J. M. Miller, A. C. Fabian, M. C. Miller, J. Homan, M. Van Der Klis, E. M. Cackett, R. C. Reis Nov 2009

Measuring The Spin Of Grs 1915+105 With Relativistic Disk Reflection, J. L. Blum, J. M. Miller, A. C. Fabian, M. C. Miller, J. Homan, M. Van Der Klis, E. M. Cackett, R. C. Reis

Physics and Astronomy Faculty Research Publications

GRS 1915+105 harbors one of the most massive known stellar black holes in the Galaxy. In 2007 May, we observed GRS 1915+105 for ~117 ks in the low/hard state using Suzaku. We collected and analyzed the data with the Hard X-ray Detector/Positive Intrinsic Negative and X-ray Spectrometer cameras spanning the energy range from 2.3 to 55 keV. Fits to the spectra with simple models reveal strong disk reflection through an Fe K emission line and a Compton backscattering hump. We report constraints on the spin parameter of the black hole in GRS 1915 + 105 using relativistic disk reflection models. …

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The Fundamental Plane Of Accretion Onto Black Holes With Dynamical Masses, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone Nov 2009

The Fundamental Plane Of Accretion Onto Black Holes With Dynamical Masses, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone

Physics and Astronomy Faculty Research Publications

Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosities are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively …

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Linker-Free Modification Of Tio2 Nanorods With Pbse Nanocrystals, Krishna P. Acharya, Taiwo R. Alabi, Nicholas Schmall, Nishshanka N. Hewa-Kasakarage, Maria Kirsanova, Alexander Nemchinov, Elena Khon, Mikhail Zamkov Nov 2009

Linker-Free Modification Of Tio2 Nanorods With Pbse Nanocrystals, Krishna P. Acharya, Taiwo R. Alabi, Nicholas Schmall, Nishshanka N. Hewa-Kasakarage, Maria Kirsanova, Alexander Nemchinov, Elena Khon, Mikhail Zamkov

Physics and Astronomy Faculty Publications

We report on a colloidal synthesis of Pbse/TiO2 heterostructures, comprising small-diameter PbSe nanocrystals epitaxially grown onto the surface of TiO2 nanorods. The deposition of lead selenide onto prefabricated TiO2 nanocrystals proceeds via formation of a thin PbSe shell that subsequently breaks into sub-2-nm islands. Additional precursor injections are then used to increase the size of PbSe nanocrystals up to 5 nm. In the case of small-size PbSe, a 2.1-ns transfer of photoinduced carriers into TiO2 domain was evidenced through quenching of the PbSe band gap emission. Overall, the present synthesis demonstrates a colloidal approach to all-inorganic modification of TiO2 surfaces …

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Validity Of The Spin-Susceptibility “Glue” Approximation For Pairing In The Two-Dimensional Hubbard Model, Ehsan Khatami, A. Macridin, M. Jarrell Nov 2009

Validity Of The Spin-Susceptibility “Glue” Approximation For Pairing In The Two-Dimensional Hubbard Model, Ehsan Khatami, A. Macridin, M. Jarrell

Faculty Publications

We examine the validity of the weak-coupling spin-susceptibility “glue” approximation (SSGA) in a two-dimensional Hubbard model for cuprates. For comparison, we employ the well-established dynamical cluster approximation (DCA) with a quantum Monte Carlo algorithm as a cluster solver. We compare the leading eigenvalues and corresponding eigenfunctions of the DCA and SSGA pairing matrices. For realistic model parameters, we find that the SSGA fails to capture the leading pairing symmetries seen in the DCA. Furthermore, when the SSGA is improved through the addition of a term with d-wave symmetry, the strength of this additional term is found to be larger than …

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The White Dwarfs Within 20 Parsecs Of The Sun: Kinematics And Statistics, Edward M. Sion, J. B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic Oct 2009

The White Dwarfs Within 20 Parsecs Of The Sun: Kinematics And Statistics, Edward M. Sion, J. B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic

Publications

We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20 pc of the Sun.We find no convincing evidence of halo white dwarfs in the total 20 pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20 pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20 pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The addition …

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