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Articles 7051 - 7080 of 8870

Full-Text Articles in Astrophysics and Astronomy

Faint Blue Objects In The Hubble Deep Field–South Revealed: White Dwarfs, Subdwarfs, And Quasars, Mukremin Kilic, Ted Von Hippel, Et Al. Nov 2005

Faint Blue Objects In The Hubble Deep Field–South Revealed: White Dwarfs, Subdwarfs, And Quasars, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We explore the nature of the faint blue objects in the Hubble Deep Field–South. We have derived proper motions for the point sources in the Hubble Deep Field–South using a 3 yr baseline. Combining our proper-motion measurements with spectral energy distribution fitting enabled us to identify four quasars and 42 stars, including three white dwarf candidates. Two of these white dwarf candidates, HDF-S 1444 and 895, are found to display significant proper motion, 21:1±7:9 and 34:9 ± 8:0 mas yr -1, and are consistent with being thick-disk or halo white dwarfs located at ̴2 kpc. The other faint …

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Spontaneous Lorentz Violation And Nonpolynomial Interactions, Brett Altschul, V. Alan Kostelecký Nov 2005

Spontaneous Lorentz Violation And Nonpolynomial Interactions, Brett Altschul, V. Alan Kostelecký

Faculty Publications

Gauge-noninvariant vector field theories with superficially nonrenormalizable nonpolynomial interactions are studied. We show that nontrivial relevant and stable theories have spontaneous Lorentz violation, and we present a large class of asymptotically free theories. The Nambu-Goldstone modes of these theories can be identified with the photon, with potential experimental implications. © 2005 Elsevier B.V. All rights reserved.

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The N2k Consortium. Ii. A Transiting Hot Saturn Around Hd 149026 With A Large Dense Core, Bun'ei Sato, Debra A. Fischer, Gregory W. Henry, Gregory Laughlin, R. Paul Butler, Geoffrey W. Marcy, Steve Vogt, Peter Bodenheimer, Shigeru Ida, Eri Toyota, Aaron S. Wolf, Jeff A. Valenti, Louis J. Boyd, John A. Johnson, Jason T. Wright, Mark Ammons, Sarah E. Robinson, Jay Strader, Chris Mccarthy, Kok Leong Tah, Dante Minniti Nov 2005

The N2k Consortium. Ii. A Transiting Hot Saturn Around Hd 149026 With A Large Dense Core, Bun'ei Sato, Debra A. Fischer, Gregory W. Henry, Gregory Laughlin, R. Paul Butler, Geoffrey W. Marcy, Steve Vogt, Peter Bodenheimer, Shigeru Ida, Eri Toyota, Aaron S. Wolf, Jeff A. Valenti, Louis J. Boyd, John A. Johnson, Jason T. Wright, Mark Ammons, Sarah E. Robinson, Jay Strader, Chris Mccarthy, Kok Leong Tah, Dante Minniti

Information Systems and Engineering Management Research Publications

Doppler measurements from Subaru and Keck have revealed radial velocity variations in the V = 8.15, G0 IV star HD 149026 consistent with a Saturn-mass planet in a 2.8766 day orbit. Photometric observations at Fairborn Observatory have detected three complete transit events with depths of 0.003 mag at the predicted times of conjunction. HD 149026 is now the second-brightest star with a transiting extrasolar planet. The mass of the star, based on interpolation of stellar evolutionary models, is 1.3 ± 0.1 M☉; together with the Doppler amplitude K1 = 43.3 m s-1, we derive a planet mass M sin i …

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The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof Nov 2005

The H Ii Region/Pdr Connection: Self-Consistent Calculations Of Physical Conditions In Star-Forming Regions, Nicholas Paul Abel, Gary J. Ferland, G. Shaw, Peter A. M. Van Hoof

Physics and Astronomy Faculty Publications

We have performed a series of calculations designed to reproduce infrared diagnostics used to determine physical conditions in star-forming regions. We self-consistently calculate the thermal and chemical structure of an H II region and photodissociation region (PDR) that are in pressure equilibrium. This differs from previous work, which used separate calculations for each gas phase. Our calculations span a wide range of stellar temperatures, gas densities, and ionization parameters. We describe improvements made to the spectral synthesis code Cloudy that made these calculations possible. These include the addition of a molecular network with ~1000 reactions involving 68 molecular species and …

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Book Review: The Scientific Legacy Of Fred Hoyle, T. D. Oswalt Nov 2005

Book Review: The Scientific Legacy Of Fred Hoyle, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Scientific Legacy of Fred Hoyle ed. by Douglas Gough Cambridge, 2004 249p, 0521824486 $75.00.

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Coordinated Cluster/Double Star Observations Of Dayside Reconnection Signatures, M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, Et Al. Nov 2005

Coordinated Cluster/Double Star Observations Of Dayside Reconnection Signatures, M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, Et Al.

Publications

The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft were on outbound transits through the dawnside magnetosphere. The observations are consistent with ongoing reconnection on the dayside magnetopause, resulting in a series of flux transfer events (FTEs) seen both at Cluster and TC-1, which appear to lie north and …

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The First-Optical-Vla Survey For Lensed Radio Lobes, Deborah B. Haarsma, Joshua N. Winn, Emilio E. Falco, Christopher S. Kochanek Nov 2005

The First-Optical-Vla Survey For Lensed Radio Lobes, Deborah B. Haarsma, Joshua N. Winn, Emilio E. Falco, Christopher S. Kochanek

University Faculty Publications and Creative Works

We present results from a survey for gravitationally lensed radio lobes. Lensed lobes are a potentially richer source of information about galaxy mass distributions than lensed point sources, which have been the exclusive focus of other recent surveys. Our approach is to identify radio lobes in the Faint Images of the Radio Sky at Twenty cm (FIRST) catalog and then search optical catalogs for coincident foreground galaxies, which are candidate lensing galaxies. We then obtain higher resolution images of these targets at both optical and radio wavelengths and obtain optical spectra for the most promising candidates. We present maps of …

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Using Genetic Algorithms To Map First-Principles Results To Model Hamiltonians: Application To The Generalized Ising Model For Alloys, Gus L. W. Hart, Volker Blum, Michael J. Walorski, Alex Zunger Oct 2005

Using Genetic Algorithms To Map First-Principles Results To Model Hamiltonians: Application To The Generalized Ising Model For Alloys, Gus L. W. Hart, Volker Blum, Michael J. Walorski, Alex Zunger

Faculty Publications

The cluster expansion method provides a standard framework to map first-principles generated energies for a few selected configurations of a binary alloy onto a finite set of pair and many-body interactions between the alloyed elements. These interactions describe the energetics of all possible configurations of the same alloy, which can hence be readily used to identify ground state structures and, through statistical mechanics solutions, find finite-temperature properties. In practice, the biggest challenge is to identify the types of interactions which are most important for a given alloy out of the many possibilities. We describe a genetic algorithm which automates this …

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Numerical Integration Of The Teukolsky Equation In The Time Domain, Enrique Pazos-Avalos, Carlos O. Lousto Oct 2005

Numerical Integration Of The Teukolsky Equation In The Time Domain, Enrique Pazos-Avalos, Carlos O. Lousto

Physics & Astronomy Faculty Publications

We present a fourth-order convergent, (2+1)-dimensional, numerical formalism to solve the Teukolsky equation in the time domain. Our approach is first to rewrite the Teukolsky equation as a system of first-order differential equations. In this way we get a system that has the form of an advection equation. This is then used in combination with a series expansion of the solution in powers of time. To obtain a fourth-order scheme we kept terms up to fourth derivative in time and use the advectionlike system of differential equations to substitute the temporal derivatives by spatial derivatives. This scheme is applied to …

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Integral Neutron Multiplicity Measurements From Cosmic Ray Interactions In Lead, Thomas E. Ward, Alexander A. Rimsky-Korsakov, Nikolai A. Kudryashev, Denis E. Beller Oct 2005

Integral Neutron Multiplicity Measurements From Cosmic Ray Interactions In Lead, Thomas E. Ward, Alexander A. Rimsky-Korsakov, Nikolai A. Kudryashev, Denis E. Beller

Transmutation Sciences Physics (TRP)

Sixty element 3He neutron multiplicity detector systems were designed, constructed and tested for use in cosmic ray experiments with a 30-cm cube lead target. A series of measurements were performed for the cosmic ray configuration at ground level (3 meters water equivalent, mwe), in the St. Petersburg metro tunnel (185 mwe), and in the Pyhäsalmi mine in Finland (583 and 1185 mwe). Anomalous coincidence events with charged cosmic ray particles at sea level produced events with 100-120 neutrons due possibly to the total disintegration of the Pb nucleus. These events were also detected at 185 mwe, but the particles …

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System Parameters Of The Transiting Extrasolar Planet Hd 209458b, Robert A. Wittenmyer, William F. Welsh, Jerome A. Orosz, A. B. Schultz, Wayne Kinzel, M. Kochte, Frederick Bruhweiler, David Bennum, Gregory W. Henry, Geoffrey W. Marcy, Debra A. Fischer, R. Paul Butler, Steve Vogt Oct 2005

System Parameters Of The Transiting Extrasolar Planet Hd 209458b, Robert A. Wittenmyer, William F. Welsh, Jerome A. Orosz, A. B. Schultz, Wayne Kinzel, M. Kochte, Frederick Bruhweiler, David Bennum, Gregory W. Henry, Geoffrey W. Marcy, Debra A. Fischer, R. Paul Butler, Steve Vogt

Information Systems and Engineering Management Research Publications

We derive improved system parameters for the HD 209458 system using a model that simultaneously fits both photometric transit and radial velocity observations. The photometry consists of previous Hubble Space Telescope STIS and FGS observations, 12 I-band transits observed between 2001 and 2003 with the Mount Laguna Observatory 1 m telescope, and six Strömgren b + y transits observed between 2001 and 2004 with two of the Automatic Photometric Telescopes at Fairborn Observatory. The radial velocities were derived from Keck HIRES observations. The model properly treats the orbital dynamics of the system and thus yields robust and physically self-consistent solutions. …

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The Baryonic Tully-Fisher Relation Of Galaxies With Extended Rotation Curves And The Stellar Mass Of Rotating Galaxies, Stacy S. Mcgaugh Oct 2005

The Baryonic Tully-Fisher Relation Of Galaxies With Extended Rotation Curves And The Stellar Mass Of Rotating Galaxies, Stacy S. Mcgaugh

Faculty Scholarship

I investigate the baryonic Tully-Fisher relation for a sample of galaxies with extended 21 cm rotation curves spanning the range 20 km s-1 ≲ Vf ≤ 300 km s-1. A variety of scalings of the stellar mass-to-light ratio Υ* are considered. For each prescription for Υ*, I give fits of the form Md = AVfx. Presumably, the prescription that comes closest to the correct value will minimize the scatter in the relation. The fit with minimum scatter has A = 50 M⊙ km-4 s4 and x = 4. This relation holds over five decades in mass. Galaxy color, stellar fraction, …

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Balance Of Dark And Luminous Mass In Rotating Galaxies, Stacy S. Mcgaugh Oct 2005

Balance Of Dark And Luminous Mass In Rotating Galaxies, Stacy S. Mcgaugh

Faculty Scholarship

A fine balance between dark and baryonic mass is observed in spiral galaxies. As the contribution of the baryons to the total rotation velocity increases, the contribution of the dark matter decreases by a compensating amount. This poses a fine-tuning problem for ÎCDM galaxy formation models, and may point to new physics for dark matter particles or even a modification of gravity.

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Excess Infrared Radiation From The Massive Daz White Dwarf Gd 362: A Debris Disk?, Mukremin Kilic, Ted Von Hippel, Et Al. Oct 2005

Excess Infrared Radiation From The Massive Daz White Dwarf Gd 362: A Debris Disk?, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We report the discovery of excess K-band radiation from the massive DAZ white dwarf star GD 362. Combining infrared photometric and spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a debris disk. This would be only the second such system known, discovered 18 years after G29-38, the only single white dwarf currently known to be orbited by circumstellar dust. Both of these systems favor a model with accretion from a surrounding debris disk to explain the metal abundances observed in DAZ white dwarfs. …

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A ~7.5 M⊕ Planet Orbiting The Nearby Star, Gj 876*, Eugenio Rivera, Jack J. Lissauer, R. Paul Butler, Geoffrey W. Marcy, Steve Vogt, Debra A. Fischer, Timothy M. Brown, Gregory Laughlin, Gregory W. Henry Oct 2005

A ~7.5 M⊕ Planet Orbiting The Nearby Star, Gj 876*, Eugenio Rivera, Jack J. Lissauer, R. Paul Butler, Geoffrey W. Marcy, Steve Vogt, Debra A. Fischer, Timothy M. Brown, Gregory Laughlin, Gregory W. Henry

Information Systems and Engineering Management Research Publications

High-precision, high-cadence radial velocity monitoring over the past 8 yr at the W. M. Keck Observatory reveals evidence for a third planet orbiting the nearby (4.69 pc) dM4 star GJ 876. The residuals of three-body Newtonian fits, which include GJ 876 and Jupiter-mass companions b and c, show significant power at a periodicity of 1.9379 days. Self-consistently fitting the radial velocity data with a model that includes an additional body with this period significantly improves the quality of the fit. These four-body (three-planet) Newtonian fits find that the minimum mass of companion "d" is m sin i = 5.89 ± …

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Direct Enumeration Of Alloy Configurations For Electronic Structural Properties, Gus L. W. Hart, Peter A. Graf, Kwiseon Kim, Wesley B. Jones Oct 2005

Direct Enumeration Of Alloy Configurations For Electronic Structural Properties, Gus L. W. Hart, Peter A. Graf, Kwiseon Kim, Wesley B. Jones

Faculty Publications

We present and apply an approach to directly enumerate the band gaps and effective masses of all possible zinc blende-based alloy configurations whose unit cell contains up to a specified number of atoms. This method allows us to map the space of band gaps and effective masses versus alloy composition and atomic configuration. We demonstrate that a large number of band gaps and effective masses are available. We also discuss convergence of the method with respect to unit cell size and the combined optimization of band gap and effective mass for AlGaAs and GaInP semiconductor alloys.

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Five New Multicomponent Planetary Systems, Steve Vogt, R. Paul Butler, Geoffrey W. Marcy, Debra A. Fischer, Gregory W. Henry, Gregory Laughlin, Jason T. Wright, John A. Johnson Oct 2005

Five New Multicomponent Planetary Systems, Steve Vogt, R. Paul Butler, Geoffrey W. Marcy, Debra A. Fischer, Gregory W. Henry, Gregory Laughlin, Jason T. Wright, John A. Johnson

Information Systems and Engineering Management Research Publications

We report Doppler measurements for six nearby G- and K-type main-sequence stars that show multiple low-mass companions, at least one of which has planetary mass. One system has three planets, the fourth triple-planet system known around a normal star, and another has an extremely low minimum mass of 18 M⊕. HD 128311 (K0 V) has two planets (one previously known) with minimum masses (M sin i) of 2.18MJ and 3.21MJ and orbital periods of 1.26 and 2.54 yr, suggesting a possible 2 : 1 resonance. For HD 108874 (G5 V), the velocities reveal two planets (one previously known) having minimum …

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Deep Photometry Of The Globular Cluster M5: Distance Estimates From White Dwarf And Main-Sequence Stars, Andrew C. Layden, Ted Von Hippel, Et Al. Oct 2005

Deep Photometry Of The Globular Cluster M5: Distance Estimates From White Dwarf And Main-Sequence Stars, Andrew C. Layden, Ted Von Hippel, Et Al.

Publications

We present deep VI photometry of stars in the globular cluster M5 (NGC 5904) based on images taken with the Hubble Space Telescope. The resulting color-magnitude diagram reaches below V ≈27 mag, revealing the upper 2–3 mag of the white dwarf cooling sequence and main-sequence stars 8 mag and more below the turnoff. We fit the main sequence to subdwarfs of known parallax to obtain a true distance modulus of (m ̶ M )0 = 14:45 ± 0:11 mag. A second distance estimate based on fitting the cluster white dwarf sequence to field white dwarfs with known parallax …

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Noao Fundamental Plane Survey. Ii. Age And Metallicity Along The Red Sequence From Line‐Strength Data, Jenica E. Nelan, Russell J. Smith, Michael J. Hudson, Gary A. Wegner Oct 2005

Noao Fundamental Plane Survey. Ii. Age And Metallicity Along The Red Sequence From Line‐Strength Data, Jenica E. Nelan, Russell J. Smith, Michael J. Hudson, Gary A. Wegner

Dartmouth Scholarship

We present spectroscopic line-strength data for 4097 red-sequence galaxies in 93 low-redshift galaxy clusters and use these to investigate variations in average stellar populations as a function of galaxy mass. Our analysis includes an improved treatment of nebular emission contamination, which affects ~10% of the sample galaxies. Using the stellar population models of D. Thomas and collaborators, we simultaneously fit 12 observed line-strength-σ relations in terms of common underlying trends of age, [Z/H] (total metallicity), and [α/Fe] (α-element enhancement). We find that the observed line-strength-σ relations can be explained only if higher mass red-sequence galaxies are, on average, …

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Limits Of Quintessence, R. R. Caldwell, Eric V. Linder Sep 2005

Limits Of Quintessence, R. R. Caldwell, Eric V. Linder

Dartmouth Scholarship

We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase plane of w and w′, the dark energy equation of state and its time derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order σ(w′)≈(1+w), …

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Hs 2331+3905: The Cataclysmic Variable That Has It All, S. Araujo-Betancor, B. T. Gänsicke, H.-J. Hagen, T. R. Marsh, E T. Harlaftis, J Thorstensen Sep 2005

Hs 2331+3905: The Cataclysmic Variable That Has It All, S. Araujo-Betancor, B. T. Gänsicke, H.-J. Hagen, T. R. Marsh, E T. Harlaftis, J Thorstensen

Dartmouth Scholarship

We report detailed follow-up observations of the cataclysmic variable HS 2331+3905, identified as an emission- line object in the Hamburg Quasar Survey. An orbital period of 81.08 min is unambiguously determined from the detection of eclipses in the light curves of HS 2331+3905. A second photometric period is consistently detected at P ≃ 83.38 min, ∼2.8% longer than Porb, which we tentatively relate to the presence of permanent superhumps. High time resolution photometry exhibits short-timescale variability on time scales of ≃5−6 min which we interpret as non-radial white dwarf pulsations, as well as a coherent signal at 1.12 min, which …

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Further Studies Of Single-Sided Charge-Sharing Czt Strip Detectors, B Donmez, John R. Macri, Mark L. Mcconnell, James M. Ryan, Mark Widholm, T Narita, L A. Hamel Sep 2005

Further Studies Of Single-Sided Charge-Sharing Czt Strip Detectors, B Donmez, John R. Macri, Mark L. Mcconnell, James M. Ryan, Mark Widholm, T Narita, L A. Hamel

Space Science Center

We report progress in the study of a thick CZT strip detector module designed to perform gamma-ray spectroscopy and 3-D imaging. We report preliminary performance measurements of 7.5 mm thick single-sided charge-sharing strip detector prototype devices. This design features both row and column contacts on the anode surface. This electron-only approach addresses problems associated with poor hole transport in CZT that limit the thickness and energy range of double-sided strip detectors. This work includes laboratory and simulation studies aimed at developing compact, efficient, detector modules for 0.05 to 1 MeV gamma measurements while minimizing the number and complexity of the …

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First Glimpse Results On The Stellar Structure Of The Galaxy., R. Benjamin, E. Churchwell, B. Babler, R. Indebetouw, M. Meade, B. Whitney, C. Watson, M. Wolfire, M. Wolff, Richard Ignace, T. Bania, S. Bracker, D. Clemens, L. Chomiuk, M. Cohen, J. Dickey, J. Jackson, H. Kobulnicky, E. Mercer, J. Mathis, S. Stolovy, B. Uzpen Sep 2005

First Glimpse Results On The Stellar Structure Of The Galaxy., R. Benjamin, E. Churchwell, B. Babler, R. Indebetouw, M. Meade, B. Whitney, C. Watson, M. Wolfire, M. Wolff, Richard Ignace, T. Bania, S. Bracker, D. Clemens, L. Chomiuk, M. Cohen, J. Dickey, J. Jackson, H. Kobulnicky, E. Mercer, J. Mathis, S. Stolovy, B. Uzpen

ETSU Faculty Works

The GLIMPSE (Galactic Legacy Mid-Plane Survey Extraordinaire) Point Source Catalog of ~ 30 million mid-infrared sources towards the inner Galaxy, 10 < |l| < 65 degrees and |b| < 1 degree, was used to determine the distribution of stars in Galactic longitude, latitude, and apparent magnitude. The counts versus longitude can be approximated by the modified Bessel function N=N_0*(l/l_0)*K_1(l/l_0), where l_0 is insensitive to limiting magnitude, band choice, and side of Galactic center: l_0= 17-30 degrees with a best fit value in the the 4.5 micron band of l_0=24 +/- 4 degrees. Modeling the source distribution as an exponential disk yields a radial scale length of H= 3.9 +/- 0.6 kpc. There is a pronounced north-south asymmetry in source counts for |l| < 30 degrees, with ~ 25% more stars in the north. For l=10-30 degrees, there is a strong enhancement of stars of m= 11.5-13.5 mag. A linear bar passing through the Galactic center with half-length R_bar=4.4 +/- 0.5 kpc, tilted by phi=44 +/- 10 degrees to the Sun-Galactic Center line, provides the simplest interpretation of this data. We examine the possibility that enhanced source counts at l=26-28 degrees, 31.5-34 degrees, and 306-309 degrees are related to Galactic spiral structure. Total source counts are depressed in regions where the counts of red objects (m_K-m_[8.0] >3) peak. In these areas, the counts are reduced by extinction due to molecular gas and/or high diffuse backgrounds associated with star formation.

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Abundance Of Elements Beyond The Iron Group In Cool Do White Dwarfs, Pierre Chayer, Stéphane Vennes, Jean Jean François, Jeffrey W. Kruk Sep 2005

Abundance Of Elements Beyond The Iron Group In Cool Do White Dwarfs, Pierre Chayer, Stéphane Vennes, Jean Jean François, Jeffrey W. Kruk

Aerospace, Physics, and Space Science Faculty Publications

We report the presence of elements beyond the iron group in the atmospheres of the cool DO white dwarfs HD 149499 B and HZ 21. Photospheric lines of germanium (Z = 32), arsenic (33), selenium (34), tin (50), tellurium (52), iodine (53), and perhaps bromine (35) are observed in ultraviolet spectra of HD 149499 B obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Goddard High Resolution Spectrograph (GHRS), and the International Ultraviolet Explorer. Germanium, arsenic, and tellurium are also observed in FUSE and GHRS spectra of HZ 21. Light elements such as carbon, silicon, phosphorus, and sulfur are present …

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Imaging Solar Neutrons Below 10 Mev In The Inner Heliosphere, U Bravar Sep 2005

Imaging Solar Neutrons Below 10 Mev In The Inner Heliosphere, U Bravar

Space Science Center

Inner heliosphere measurements of the Sun can be conducted with the proposed Solar Sentinel spacecraft and mission. One of the key measurements that can be made inside the orbit of the Earth is that of lower energy neutrons that arise in flares from nuclear reactions. Solar flare neutrons below 10 MeV suffer heavy weak-decay losses before reaching 1 AU. For heliocentric radii as close as 0.3 AU, the number of surviving neutrons from a solar event is dramatically greater. Neutrons from 1-10 MeV provide a new measure of heavy ion interactions at low energies, where the vast majority of energetic …

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Galactic Open Clusters, Ted Von Hippel Sep 2005

Galactic Open Clusters, Ted Von Hippel

Publications

The study of open clusters has a classic feel to it since the subject predates anyone alive today. Despite the age of this topic, I show via an ADS search that its relevance and importance in astronomy has grown faster in the last few decades than astronomy in general. This is surely due to both technical reasons and the interconnection of the field of stellar evolution to many branches of astronomy. In this review, I outline what we know today about open clusters and what they have taught us about a range of topics from stellar evolution to Galactic structure …

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Caster: A Concept For A Black Hole Finder Probe Based On The Use Of New Scintillator Technologies, Mark L. Mcconnell, Peter F. Bloser, G L. Case, M L. Cherry, J Cravens, T G. Guzik, K Hurley, R M. Kippen, John R. Macri, R S. Miller, W Paciesas, James M. Ryan, B Schaefer, J G. Stacy, W T. Vestrand, J P. Wefel Sep 2005

Caster: A Concept For A Black Hole Finder Probe Based On The Use Of New Scintillator Technologies, Mark L. Mcconnell, Peter F. Bloser, G L. Case, M L. Cherry, J Cravens, T G. Guzik, K Hurley, R M. Kippen, John R. Macri, R S. Miller, W Paciesas, James M. Ryan, B Schaefer, J G. Stacy, W T. Vestrand, J P. Wefel

Space Science Center

The primary scientific mission of the Black Hole Finder Probe (BHFP), part of the NASA Beyond Einstein program, is to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X-ray coded-aperture imaging mission operating in the 10-600 keV energy band, a spectral range that is considered to be especially useful in the detection of black hole sources. The development of new inorganic scintillator materials provides improved performance (for example, with regards to energy resolution and timing) that is well suited to the BHFP science …

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Mega: A Medium-Energy Gamma-Ray Astronomy Mission Concept, Peter F. Bloser, James M. Ryan, Mark L. Mcconnell, John R. Macri, U Bravar, G Kanbach, R Andritsche, M Ajello, A Zoglauer, S Hunter, B F. Phlips, Eric Wulf, Dieter H. Hartman, R S. Miller, W Paciesas, Allen Zych, R M. Kippen, W T. Vestrand, M L. Cherry, T G. Guzik, J G. Stacy, J P. Wefel, V Reglero, G Dicocco, J Cravens Sep 2005

Mega: A Medium-Energy Gamma-Ray Astronomy Mission Concept, Peter F. Bloser, James M. Ryan, Mark L. Mcconnell, John R. Macri, U Bravar, G Kanbach, R Andritsche, M Ajello, A Zoglauer, S Hunter, B F. Phlips, Eric Wulf, Dieter H. Hartman, R S. Miller, W Paciesas, Allen Zych, R M. Kippen, W T. Vestrand, M L. Cherry, T G. Guzik, J G. Stacy, J P. Wefel, V Reglero, G Dicocco, J Cravens

Space Science Center

The Medium Energy Gamma-ray Astronomy (MEGA) telescope concept will soon be proposed as a MIDEX mission. This mission would enable a sensitive all-sky survey of the medium-energy gamma-ray sky (0.4 - 50 MeV) and bridge the huge sensitivity gap between the COMPTEL and OSSE experiments on the Compton Gamma Ray Observatory, the SPI and IBIS instruments on INTEGRAL, and the visionary Advanced Compton Telescope (ACT) mission. The scientific goals include, among other things, compiling a much larger catalog of sources in this energy range, performing far deeper searches for supernovae, better measuring the galactic continuum and line emissions, and identifying …

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Gas Micro-Well Track Imaging Detectors For Gamma-Ray Astronomy, Peter F. Bloser, S Hunter, James M. Ryan, Mark L. Mcconnell, John R. Macri Sep 2005

Gas Micro-Well Track Imaging Detectors For Gamma-Ray Astronomy, Peter F. Bloser, S Hunter, James M. Ryan, Mark L. Mcconnell, John R. Macri

Space Science Center

We describe our program to develop gas micro-well detectors (MWDs) as three-dimensional charged particle trackers for use in advanced gamma-ray telescope concepts. A micro-well detector consists of an array of individual micro-patterned gas proportional counters opposite a planar drift electrode. The well anodes and cathodes may be connected in X and Y strips, respectively, to provide two-dimensional imaging. When combined with transient digitizer electronics, which record the time signature of the charge collected in the wells of each strip, full three-dimensional reconstruction of charged-particle tracks in large gas volumes is possible. Such detectors hold great promise for advanced Compton telescope …

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Book Review: Observing Variable Stars, Novae, And Supernovae, T. D. Oswalt Sep 2005

Book Review: Observing Variable Stars, Novae, And Supernovae, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Observing Variable Stars, Novae, and Supernovae by Gerald North with Nick James Cambridge, 2004 230p, 0521820472 $45.00.

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