Astrophysics and Astronomy Commons^™

Abundances Of Stars With Planets: Trends With Condensation Temperature, Simon C. Schuler, Davin Flateau, Katia Cunha, Jeremy R. King, Luan Ghezzi, Verne V. Smith

Jeremy R King

Precise abundances of 18 elements have been derived for 10 stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically 0.05 dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (Tc) of the elements in the sense of increasing abundances with increasing Tc; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with Tc, although slopes of linear least-square fits to the [m/H]–Tc relations …

The Meaning Of Wise Colours – I. The Galaxy And Its Satellites, Robert Nikutta, Nicholas Hunt-Walker, Maia M. Nenkova, Željko Ivezić, Moshe Elitzur

Physics and Astronomy Faculty Publications

Through matches with the Sloan Digital Sky Survey (SDSS) catalogue we identify the location of various families of astronomical objects in WISE colour space. We identify reliable indicators that separate Galactic/local from extragalactic sources and concentrate here on the objects in our Galaxy and its closest satellites. We develop colour and magnitude criteria that are based only on WISE data to select asymptotic giant branch (AGB) stars with circumstellar dust shells, and separate them into O-rich and C-rich classes. With these criteria we produce an all-sky map for the count ratio of the two populations. The map reveals differences between …

Measuring Noble Gases In Coma Samples From Comet Wild 2, Jacob Simones

Journal of Undergraduate Research at Minnesota State University, Mankato

Since comets originated during the formation of the solar system, the processes of solar system formation can be better understood through compositional analysis of cometary material. A low density, silicon-based substance called aerogel was used by NASA’s Stardust spacecraft to collect coma samples from comet Wild 2. Aerogel not from the spacecraft (“non-flight”) was investigated to determine the possibility of measuring noble gases in Stardust samples. Gas evolved from heated, non-flight aerogel was measured initially using a residual gas analyzer, then a high-sensitivity massspectrometer. Levels of helium and neon isotopes observed from both instruments were sufficiently low that noble gases …

Observational Signatures From Self-Gravitating Protostellar Disks, Alexander L. Desouza

Electronic Thesis and Dissertation Repository

Protostellar disks are the ubiquitous corollary outcome of the angular momentum conserving, gravitational collapse of molecular cloud cores into stars. Disks are an essential component of the star formation process, mediating the accretion of material onto the protostar, and for redistributing excess angular momentum during the collapse. We present a model to explain the observed correlation between mass accretion rates and stellar mass that has been inferred from observations of intermediate to upper mass T Tauri stars. We explain this correlation within the framework of gravitationally driven torques parameterized in terms of Toomre’s Q criterion. Our models reproduce both the …

Inferring The Global Cosmic Dust Influx To The Earth’S Atmosphere From Lidar Observations Of The Vertical Flux Of Mesospheric Na, Chester S. Gardner, Alan Z. Liu, Dan Marsh, Wuhu Feng, John Plane

Alan Z Liu

Measurement Of Longitudinal Spin Asymmetries For Weak Boson Production In Polarized Proton-Proton Collisions At Rhic, J. Kevin Adkins, Renee Fatemi, Suvarna Ramachandran, G. Webb, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer

Physics and Astronomy Faculty Publications

We report measurements of single- and double-spin asymmetries for W^± and Z/γ^∗ boson production in longitudinally polarized p+p collisions at √^S=510  GeV by the STAR experiment at RHIC. The asymmetries for W^± were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton’s polarized quark distributions at the scale of the W mass. The results are compared to theoretical predictions, constrained by polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range 0.05<x<0.2.

Elastic Properties Of The Zintl Ferromagnet Yb14mnsb11, Sriparna Bhattacharya, D C. Marinescu, James R. Morris, Ivan A. Sergienko, Brian Sales, David Madrus, Veerle Keppens

Domnita Catalina Marinescu

We report measurements of the elastic moduli as a function of temperature (5–300) K and magnetic field (0–2 T) for the Zintl ferromagnet Yb14MnSb11, which is believed to be a rare example of an underscreened Kondo lattice. The elastic moduli measured below the Curie temperature in this complex ferromagnet exhibit unusual lattice stiffening that is independent of the magnetic field and can be adequately modeled using the Landau theory.

Nonadiabatic Generation Of A Pure Spin Current In A One-Dimensional Quantum Ring With Spin-Orbit Interaction, Marian Nita, D C. Marinescu, Andrei Manolescu, Vidar Gudmundsson

Domnita Catalina Marinescu

We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a nonadiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal phase difference φ. The solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and they are used to calculate the time-dependent charge and spin currents. We find that there are critical values of φ at which the charge current disappears, while the spin current reaches a maximum or a minimum value.

Weak Localization In A Lateral Superlattice With Rashba And Dresselhaus Spin-Orbit Interaction, D C. Marinescu, Andrei Manolescu

Domnita Catalina Marinescu

We calculate the weak localization (WL) correction to the conductivity of a lateral superlattice (LSL) with Rashba (R)-Dresselhaus (D) spin-orbit interaction (SOI). The superlattice is modeled as a sequence of parallel wires that support tunneling between adjacent sites, leading to the formation of extended Bloch states along its axis and a miniband in the energy spectrum. Our results, obtained by calculating the eigenvalues of the Cooperon operator in the diffusion approximation, indicate that the electron dephasing rate that determines the antilocalization correction is enhanced by a term proportional with the LSL potential and the bandwidth. Within the same formalism, the …

Topological Thermoelectric Effects In Spin-Orbit Coupled Electron- And Hole-Doped Semiconductors, E Dumitrescu, Chuanwei Zhang, D C. Marinescu, Sumanta Tewari

Domnita Catalina Marinescu

We compute the intrinsic contributions to the Berry-phase mediated anomalous Hall and Nernst effects in electron- and hole-doped semiconductors in the presence of an in-plane magnetic field as well as Rashba and Dresselhaus spin-orbit couplings. For both systems we find that the regime of chemical potential which supports the topological superconducting state in the presence of the superconducting proximity effect can be characterized by plateaus in the topological Hall and Nernst coefficients flanked by well-defined peaks marking the emergence of the topological regime. The plateaus arise from a clear momentum space separation between the region where the Berry curvature is …

Thermal Conductance Of A Two-Channel Kondo Model, C P. Moca, A Roman, D C. Marinescu

Domnita Catalina Marinescu

A theory of thermal transport in a two-channel Kondo system, such as the one formed by a small quantum dot coupled to two leads and to a larger dot, is formulated. The interplay of the two screening constants allow an exploration of the Fermi liquid and non-Fermi liquid regimes. By using analytical, as well as numerical, renormalization group methods, we study the temperature dependence of the thermal conductance and the Lorentz number. We find that in the low-temperature limit, the Lorentz number attains its universal value, irrespective of the nature of the ground state.

Electronic Charge And Spin Density Distribution In A Quantum Ring With Spin-Orbit And Coulomb Interactions, Csaba Daday, Andrei Manolescu, D C. Marinescu, Vidar Gudmundsson

Domnita Catalina Marinescu

Charge and spin density distributions are studied within a nanoring structure endowed with Rashba and Dresselhaus spin-orbit interactions (SOIs). For a small number of electrons, in the presence of an external magnetic field and of the Coulomb interaction, the energy spectrum of the system is calculated through an exact numerical diagonalization procedure. The eigenstates thus determined are used to estimate the charge and spin densities around the ring. We find that when more than two electrons are considered, the charge density deformations induced by SOIs are dramatically flattened by the Coulomb repulsion, while the spin density deformations are amplified.

Spin Mass Of An Electron Liquid, Zhixin Qian, Giovanni Vignale, D C. Marinescu

Domnita Catalina Marinescu

We show that in order to calculate correctly the spin current carried by a quasiparticle in an electron liquid one must use an effective ‘‘spin mass’’ ms that is larger than both the band mass mb, which determines the charge current, and the quasiparticle effective mass m, which determines the heat capacity. We present two independent estimates of the spin mass enhancement, ms=mb, in two- and three-dimensional electron liquids, based on (i) previously calculated values of the Landau parameters and (ii) a recent theory of the dynamical local field factor in the spin channel. Both methods yield a significant spin …

Helical Antiferromagnetic Ordering In The Lowest Landau Level Of A Semiconductor Superlattice, Liqiu Zheng, D C. Marinescu

Domnita Catalina Marinescu

When subjected to a tilted magnetic field, the ground state of a semiconductor superlattice (SL) with two identical quantum wells per unit cell is shown to exhibit different magnetic configurations that are dependent on the strength and direction of the field and the SL characteristics. Intra- and interunit cell tunneling between the wells, assumed to be infinitely attractive, generate an energy miniband structure of the lowest Landau level that, in cooperation with the Zeeman splitting, creates, at certain points in the momentum space, an energy difference between opposite-spin single-particle states that can be overcome by the Coulomb interaction. Within the …

J/Ψ Production At Low PT In Au + Au And Cu + Cu Collisions At √SNn = 200 Gev With The Star Detector, J. Kevin Adkins, Renee Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin

Physics and Astronomy Faculty Publications

The J/ψ p_T spectrum and nuclear modification factor (R_AA) are reported for p_T < 5 GeV/c and |y| < 1 from 0% to 60% central Au + Au and Cu + Cu collisions at √^SNN = 200 GeV at STAR. A significant suppression of p_T-integrated J/ψ production is observed in central Au + Au events. The Cu + Cu data are consistent with no suppression, although the precision is limited by the available statistics. R_AA in Au + Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with p_T. The data are compared to high-p_{T …}

Star Formation Quenching In High-Redshift Large-Scale Structure: Post-Starburst Galaxies In The Ci 1604 Supercluster At Z ~ 0.9, Po-Feng Wu, Roy R. Gal, Brian C. Lemaux, Dale D. Kocevski, Lori M. Lubin, Nicholas Rumbaugh, Gordon K. Squires

Physics and Astronomy Faculty Publications

The Cl 1604 supercluster at z ~ 0.9 is one of the most extensively studied high-redshift large-scale structures, with more than 500 spectroscopically confirmed members. It consists of eight clusters and groups, with members numbering from a dozen to nearly a hundred, providing a broad range of environments for investigating the large-scale environmental effects on galaxy evolution. Here we examine the properties of 48 post-starburst galaxies in Cl 1604, comparing them to other galaxy populations in the same supercluster. Incorporating photometry from ground-based optical and near-infrared imaging, along with Spitzer mid-infrared observations, we derive stellar masses for all Cl 1604 …

The Green Bank Northern Celestial Cap Pulsar Survey. I. Survey Description Data Analysis And Initial Results, K. Stovall, R. S. Lynch, S. M. Ransom, A. M. Archibald, S. Banaszak, C. M. Biwer, J. Boyles, L. P. Dartez, D. Day, A. J. Ford, J. Flanigan, A. Garcia, J. W.T. Hessels, J. Hinojosa, F. A. Jenet, D. L. Kaplan, C. Karako-Argaman, V. M. Kaspi, V. I. Kondratiev, S. Leake, D. R. Lorimer, G. Lunsford, J. G. Martinez, A. Mata, M. A. Mclaughlin, M. S.E. Roberts, M. D. Rohr, X. Siemens, I. H. Stairs, J. Van Leeuwen

Physics and Astronomy Faculty Publications and Presentations

We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts, at 350 MHz using the Green Bank Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4096 channels every 81.92 μs. This survey will cover the entire sky visible to the Green Bank Telescope (δ > -40°, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure (<30 pc cm-3) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of -1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214+5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636+5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 M J). PSR J0645+5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434+7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816+4510 is an eclipsing MSP in a short-period orbit (8.7 hr) and may have recently completed its spin-up phase. © 2014. The American Astronomical Society. All rights reserved..

Discovery Of Co Gas In The Inner Disk Of Tw Hydrae, Terrence W. Rettig, Joe Haywood, Theodore Simon, Sean D. Brittain, Erika Gibb

Sean D Brittain

We report the detection of rovibrationally excited CO emission from the inner disk of the classical T Tauri star (cTTS) TW Hya. We observe ~6 × 1021 g of CO gas with a rotational temperature of 430 ± 40 K. The linearity of the excitation plot suggests that the CO is optically thin. Atypical for cTTSs, hot CO was not detected, implying that TW Hya has cleared its inner disk region out to a radial distance of ~0.5 AU. We discuss implications for the structure of the disk as it relates to replenishment and planet formation.

Post-Outburst Observations Of V1647 Orionis: Detection Of A Brief Warm Molecular Outflow, Sean D. Brittain, Terrence W. Rettig, Theodore Simon, Dinshaw S. Balsara, David Tilley, Erika Gibb, Kenneth H. Hinkle

Sean D Brittain

We present new observations of the fundamental rovibrational CO spectrum of V1647 Ori, the young star whose recent outburst illuminated McNeil's Nebula. Previous spectra, acquired during outburst in 2004 February and July, had shown the CO emission lines to be broad and centrally peaked, similar to the CO spectrum of a typical classical T Tauri star. In this Letter, we present CO spectra acquired shortly after the luminosity of the source returned to its pre-outburst level (2006 February) and roughly 1 year later (2006 December and 2007 February). The spectrum taken in 2006 February revealed blueshifted CO absorption lines superimposed …

Infrared High-Resolution Spectroscopy Of Post-Agb Circumstellar Disks. I. Hr 4049: The Winnowing Flow Observed?, Kenneth H. Hinkle, Sean D. Brittain, David L. Lambert

Sean D Brittain

High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The spectrum of HR 4049 appears principally in emission through the 3 and 4.6 micron region and in absorption in the 2 micron region. The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the spectral lines observed in the 2.3-4.6 micron spectrum are shown to be circumbinary in origin. The presence of OH and H2O …