Physical Sciences and Mathematics | Open Access Articles

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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Measurement Of Bottom Versus Charm As A Function Of Transverse Momentum With Electron-Hadron Correlations In P Þ P Collisions At Square Root Of S = 200 Gev, Andrew Marshall Adare, Sergey V. Afanasiev, Christine A. Aidala, N. N. Ajitanand, Yasuyuki Akiba, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann, S. Rembeczki, Klaus Dehmelt

Aerospace, Physics, and Space Science Faculty Publications

The momentum distribution of electrons from semileptonic decays of charm and bottom quarks for midrapidity jyj < 0:35 in p þ p collisions at ffiffi s p ¼ 200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range 2 < pT < 7 GeV=c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D=D ! e KX (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV=c in pT. A fixed-order-plus-next-to-leading-log perturbative quantum chromodynamics calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is bb ¼ 3:2þ1:2 1:1ðstatÞ þ1:4 1:3ðsystÞb.

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Variability Timescales In The M87 Jet: Signatures Of E^2 Losses, Discovery Of A Quasi Period In Hst-1, And The Site Of Tev Flaring, Daniel E. Harris, Chi C. Cheung, Łukasz Stawarz, J. A. Biretta, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

We investigate the variability timescales in the jet of M87 with two goals. The first is to use the rise times and decay times in the radio, ultraviolet, and X-ray light curves of HST-1 to constrain the source size and the energy loss mechanisms affecting the relativistic electron distributions. HST-1 is the first jet knot clearly resolved from the nuclear emission by Chandra and is the site of the huge flare of 2005. We find clear evidence for a frequency-dependent decrease in the synchrotron flux being consistent with E 2 energy losses. Assuming that this behavior is predominantly caused by …

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Gluon-Spin Contribution To The Proton Spin From The Double-Helicity Asymmetry In Inclusive Π0 Production In Polarized P+P Collisions At Square Root Of S = 200 Gev, Andrew Marshall Adare, Sergey V. Afanasiev, Christine A. Aidala, N. N. Ajitanand, Yasuyuki Akiba, H. Al-Bataineh, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann, S. Rembeczki

Aerospace, Physics, and Space Science Faculty Publications

The double helicity asymmetry in neutral pion production for pT ¼ 1 to 12 GeV=c was measured with the PHENIX experiment to access the gluon-spin contribution, G, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of 2 ¼ 4 GeV2 a next to leading order QCD analysis gives G½0:02;0:3 ¼ 0:2, with a constraint of 0:7 < G½0:02;0:3 < 0:5 at 2 ¼ 9 (3) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the G constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

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Composition And Spectral Properties Of The 1 Au Quiet-Time Superthermal Ion Population During Solar Cycle 23, M. A. Dayeh, M. I. Desai, Joseph R. Dwyer, Hamid K. Rassoul, G. M. Mason, J. E. Mazur

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed the spectral and compositional properties of suprathermal heavy ions during quiet times from 1995 January 1 to 2007 December 31 using Wind/Energetic Particles: Anisotropy, Composition, and Transport/SupraThermal-through-Energetic Particle Telescope and Advanced Composition Explorer/Ultra-low Energy Isotope Spectrometer at energies between 0.04 and 2.56 MeV nucleon−1. We find the following. (1) Quiet-time Fe/O and C/O abundances are correlated with solar cycle activity, reflecting corresponding values measured in solar energetic particle and interplanetary (IP) shock events during solar maximum, and those measured in the solar wind and corotating interaction regions (CIRs) during solar minimum conditions. (2) The 3He/4He ratio lies …

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Hubble Space Telescope Observations Of The Quasar Pks 0637-752: Equipartition Electron-Proton Jet From The Most Complete Spectral Coverage To Date, Kushal T. Mehta, Markos Georganopoulos, Eric S. Perlman, Charles A. Padgett, George Chartas

Aerospace, Physics, and Space Science Faculty Publications

We present new Near-Infrared Camera and Multi-Object Spectrometer and attitude control system observations of the quasar jet PKS 0637-752, and we use them, together with existing multiwavelength observations, to produce the most complete spectral coverage of the source to date. We explore the implications of these observations in the context of models for the jet X-ray emission. By relaxing the assumption of equipartition, we undertake an exhaustive study of the parameter space for external Compton off the cosmic microwave background (CMB) (EC/CMB) model. We find that the multiwavelength observations exclude a magnetic-field-dominated jet. Using the method proposed by Georganopoulos et …

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Remote Measurements Of Thundercloud Electrostatic Fields, Joseph R. Dwyer, Martin A. Uman, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Analytical and numerical models of the radio frequency emissions produced by relativistic runaway electron avalanches initiated by cosmic ray extensive air showers are presented. It is found that single-point measurements of the distant electromagnetic fields allow the remote determination of the electrostatic field in the runaway electron avalanche region. For instance, it is possible to use ground-based and/or remote airborne measurements of the radio frequency pulses from the runaway electron avalanches to map the magnitudes and directions of the electrostatic field within a thundercloud for regions with electric fields above the runaway avalanche threshold. Such measurements, which are difficult to …

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Preliminary Xcov26 Results For Ec14012-1446, Judith L. Provençal, Matt A. Wood, Stéphane Vennes

Aerospace, Physics, and Space Science Faculty Publications

EC14012-1446 is a hydrogen atmosphere (DA) white dwarf pulsator. Its rich pulsation spectrum displays a range of excited modes with complex multiplet structure, in addition to numerous combination frequencies. In April 2008, EC14012-1446 was the primary target of XCOV26. We obtained over 300 hrs of nearly continuous high speed photometry with the goal of using the nonlinear pulse shapes to empirically determine the parameters of the convection zone. The Fourier transform (FT) of the light curve contains power between 1000 to 4000 μHz, with the dominant peak at 1234 μHz. We find 13 independent frequencies distributed in 8 modes, as …

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Spectral Dependence Of Terrestrial Gamma-Ray Flashes On Source Distance, Bryna J. Hazelton, Brian W. Grefenstette, David M. Smith, Joseph R. Dwyer, Xuanmin Shao, Steven A. Cummer, Themis G. Chronis, Erin H. Lay, Robert H. Holzworth

Aerospace, Physics, and Space Science Faculty Publications

We use lightning sferics from the World Wide Lightning Location Network to identify storms near 362 Terrestrial Gamma-ray Flashes (TGFs). The combined spectrum of TGFs with storms within 300 km of the sub-satellite point is much harder than the spectrum of TGFs with more distant storms. When these data are compared with simulations of vertically oriented relativistic runaway breakdown, it is found that the most likely model has a source altitude of 15 km and a wide-beam geometry. We find four associations of TGFs with individual sferics geolocated to positions more than 300 km from the sub-satellite point and show …

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Multi-Site Photometry Of The Pulsating Herbig Ae Star V346 Ori, S Bernabei, T D. Oswalt

Aerospace, Physics, and Space Science Faculty Publications

Context. The study of pulsation in pre-main-sequence intermediate-mass stars represents an important tool for deriving information about fundamental stellar parameters and internal structure, as well as testing theoretical models. Interest in this class of variable stars has increased significantly during the last decade and about 30 members are presently known in the literature. Aims. After constructing the frequency spectrum of oscillations in V346 Ori, we apply asteroseismic tools to these data to estimate the intrinsic parameters (mass, luminosity, effective temperature) of V346 Ori and obtain information about its internal structure. Methods. CCD time-series photometry in the Johnson V filter was …

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Studies Of Magnetotail Dynamics And Energy Evolution During Substorms Using Mhd Simulations, S Brogl, Ramon E. Lopez, Michael J. Wiltberger, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

We examine the distribution and propagation of energy in the plasma sheet and lobes using observations and simulations for three substorms. The substorms occurred on 9 March 1995, 10 December 1996, and 27 August 2001 and have been simulated using the Lyon-Fedder-Mobarry magneto-hydrodynamic code. All three events occur over North America and show a clear substorm current wedge over the ground magnetometer chains of Alaska, Canada, and Greenland. The three simulations show the thinning of the plasma sheet during the growth phase of the event and an increase in the relative amount of thermal energy due to the compression of …

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Fuse Observations Of Intermediate Temperature Da: Atmospheric Parameters And Metal Abundances, Jean François Dupuis, Vincent Hénault-Brunet, Perre Chayer, Stéphane Vennes, Jeffrey W. Kruk

Aerospace, Physics, and Space Science Faculty Publications

We present results from our analysis of a sample of DA white dwarfs having effective temperature below 25,000 K observed with the FUSE satellite with the goals of better understanding the origin of metals detected in the atmosphere of these stars. When possible, we combine the FUSE spectra with the IUE spectra and determine atmospheric parameters by fitting the Lyman line profiles. In general we find a good agreement with published values based on fits of the Balmer series. We observe that the continuum in the blue wing of the Lyman α line profile is generally lower in comparison with …

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Photon-Hadron Jet Correlations In P+P And Au+Au Collisions At √Snn = 200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, S. Rembeczki

Aerospace, Physics, and Space Science Faculty Publications

We report the observation at the Relativistic Heavy Ion Collider of suppression of back-to-back correlations in the direct photon+jet channel in Au+Au relative to p+p collisions. Two-particle correlations of direct photon triggers with associated hadrons are obtained by statistical subtraction of the decay photon-hadron (γ-h) background. The initial momentum of the away-side parton is tightly constrained, because the parton-photon pair exactly balance in momentum at leading order in perturbative quantum chromodynamics, making such correlations a powerful probe of the in-medium parton energy loss. The away-side nuclear suppression factor, IAA, in central Au+Au collisions, is 0.32±0.12stat±0.09syst for hadrons of 3

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Full-Text Articles in Physical Sciences and Mathematics

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

Aerospace, Physics, and Space Science Faculty Publications

Variability Timescales In The M87 Jet: Signatures Of E^2 Losses, Discovery Of A Quasi Period In Hst-1, And The Site Of Tev Flaring, Daniel E. Harris, Chi C. Cheung, Łukasz Stawarz, J. A. Biretta, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

Aerospace, Physics, and Space Science Faculty Publications

Composition And Spectral Properties Of The 1 Au Quiet-Time Superthermal Ion Population During Solar Cycle 23, M. A. Dayeh, M. I. Desai, Joseph R. Dwyer, Hamid K. Rassoul, G. M. Mason, J. E. Mazur

Aerospace, Physics, and Space Science Faculty Publications

Hubble Space Telescope Observations Of The Quasar Pks 0637-752: Equipartition Electron-Proton Jet From The Most Complete Spectral Coverage To Date, Kushal T. Mehta, Markos Georganopoulos, Eric S. Perlman, Charles A. Padgett, George Chartas

Aerospace, Physics, and Space Science Faculty Publications

Remote Measurements Of Thundercloud Electrostatic Fields, Joseph R. Dwyer, Martin A. Uman, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Preliminary Xcov26 Results For Ec14012-1446, Judith L. Provençal, Matt A. Wood, Stéphane Vennes

Aerospace, Physics, and Space Science Faculty Publications

Spectral Dependence Of Terrestrial Gamma-Ray Flashes On Source Distance, Bryna J. Hazelton, Brian W. Grefenstette, David M. Smith, Joseph R. Dwyer, Xuanmin Shao, Steven A. Cummer, Themis G. Chronis, Erin H. Lay, Robert H. Holzworth

Aerospace, Physics, and Space Science Faculty Publications

Multi-Site Photometry Of The Pulsating Herbig Ae Star V346 Ori, S Bernabei, T D. Oswalt

Aerospace, Physics, and Space Science Faculty Publications

Studies Of Magnetotail Dynamics And Energy Evolution During Substorms Using Mhd Simulations, S Brogl, Ramon E. Lopez, Michael J. Wiltberger, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Fuse Observations Of Intermediate Temperature Da: Atmospheric Parameters And Metal Abundances, Jean François Dupuis, Vincent Hénault-Brunet, Perre Chayer, Stéphane Vennes, Jeffrey W. Kruk

Aerospace, Physics, and Space Science Faculty Publications

Photon-Hadron Jet Correlations In P+P And Au+Au Collisions At √Snn = 200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, S. Rembeczki

Aerospace, Physics, and Space Science Faculty Publications