Open Access. Powered by Scholars. Published by Universities.®

Astrophysics and Astronomy Commons™

Open Access. Powered by Scholars. Published by Universities.®

2009

Discipline
Institution
Keyword
Publication
Publication Type

Articles 91 - 120 of 245

Full-Text Articles in Astrophysics and Astronomy

Extreme Ultraviolet Polarimetry With Laser-Generated High-Order Harmonics: Characterization Of Uranium, Nicole Brimhall Jul 2009

Extreme Ultraviolet Polarimetry With Laser-Generated High-Order Harmonics: Characterization Of Uranium, Nicole Brimhall

Theses and Dissertations

We developed an extreme ultraviolet (EUV) polarimeter, which employs laser-generated high-order harmonics as the light source. This relatively high-flux, directional EUV source has available wavelengths between 10 nm and 47 nm with easily rotatable linear polarization. The polarimeter has allowed us to characterize the optical constants of materials that may be useful for EUV optics. The instrument has a versatile positioning system and a spectral resolution of about 180, and we have demonstrated that reflectance as low as 0.1% can be measured repeatably at EUV wavelengths. We investigate the high harmonic source used for polarimetry measurements by documenting the spatial …

Go to article

Observation Of A Kilogram-Scale Oscillator Near Its Quantum Ground State, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano Jul 2009

Observation Of A Kilogram-Scale Oscillator Near Its Quantum Ground State, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano

Physics & Astronomy Faculty Publications

We introduce a novel cooling technique capable of approaching the quantum ground state of a kilogram-scale system-an interferometric gravitational wave detector. The detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) operate within a factor of 10 of the standard quantum limit (SQL), providing a displacement sensitivity of 10-18 m in a 100 Hz band centered on 150 Hz. With a new feedback strategy, we dynamically shift the resonant frequency of a 2.7 kg pendulum mode to lie within this optimal band, where its effective temperature falls as low as 1.4μK, and its occupation number reaches about 200 quanta. This work …

Go to article

Energy Current Imaging Method For Time Reversal In Elastic Media, Brian E. Anderson, Michele Griffa, Robert A. Guyer, Paul A. Johnson, Carene Larmat, Pierre-Yves Le Bas, Timothy J. Ulrich Jul 2009

Energy Current Imaging Method For Time Reversal In Elastic Media, Brian E. Anderson, Michele Griffa, Robert A. Guyer, Paul A. Johnson, Carene Larmat, Pierre-Yves Le Bas, Timothy J. Ulrich

Faculty Publications

An energy current imaging method is presented for use in locating sources of wave energy during the back propagation stage of the time reversal process. During the back propagation phase of an ideal time reversal experiment, wave energy coalesces from all angles of incidence to recreate the source event; after the recreation, wave energy diverges in every direction. An energy current imaging method based on this convergence/divergence behavior has been developed. The energy current imaging method yields a smaller spatial distribution for source reconstruction than is possible with traditional energy imaging methods.

Go to article

Observation Of A Kilogram-Scale Oscillator Near Its Quantum Ground State, B. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. 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, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, M. Bastarrika, K. Bayer, J. Betzwieser, P. T. Beyersdorf, I. A. Bilenko, Tiffany Z. Summerscales Jul 2009

Observation Of A Kilogram-Scale Oscillator Near Its Quantum Ground State, B. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. 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, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, M. Bastarrika, K. Bayer, J. Betzwieser, P. T. Beyersdorf, I. A. Bilenko, Tiffany Z. Summerscales

Faculty Publications

We introduce a novel cooling technique capable of approaching the quantum ground state of a kilogram-scale system-an interferometric gravitational wave detector. The detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) operate within a factor of 10 of the standard quantum limit (SQL), providing a displacement sensitivity of 10-18 m in a 100 Hz band centered on 150 Hz. With a new feedback strategy, we dynamically shift the resonant frequency of a 2.7 kg pendulum mode to lie within this optimal band, where its effective temperature falls as low as 1.4μK, and its occupation number reaches about 200 quanta. This work …

Go to article

Verifying Predictions Of The L13 Crystal Structure In Cd-Pt And Pd-Pt By Exhaustive Enumeration, Gus L. W. Hart Jul 2009

Verifying Predictions Of The L13 Crystal Structure In Cd-Pt And Pd-Pt By Exhaustive Enumeration, Gus L. W. Hart

Faculty Publications

In 2001, S. Müller and A. Zunger [Phys. Rev. Lett. 87, 165502 (2001)] predicted a never-before-observed crystal structure in Ag-Pd. Recently, Curtarolo predicted the same structure to be stable in Pt-Cd and Pt-Pd [S. Curtarolo et. Al., CALPHAD: Comput. Coupling Phase Diagrams Thermochem. 29, 163 (2005)]. The predicted structure is unique in several ways. though never seen in any other face-centered-cubic-based intermetallic binary compound or ordered alloy, it is relatively simple—it contains only four atoms per unit cell. Furthermore, the structure is the only one of this small size, except the L12 structure, that cannot be characterized as a simple …

Go to article

Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho Bonev, Michael Mumma, Erika Gibb, Michael Disanti, Geronimo Villanueva, Karen Magee-Sauer, Richard Ellis Jul 2009

Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho Bonev, Michael Mumma, Erika Gibb, Michael Disanti, Geronimo Villanueva, Karen Magee-Sauer, Richard Ellis

Physics Faculty Works

High-dispersion (λ/δλ ≈ 25,000) infrared spectra of Comet C/2004 Q2 (Machholz) were acquired on 2004 November 28-29, and 2005 January 19 (UT dates) with the Near InfraRed echelle SPECtrograph (NIRSPEC) at the Keck-2 telescope on Mauna Kea. We detected H2O, CH4, C2H2, C2H6, CO, H2CO, CH3OH, HCN, and NH3 and we conducted a sensitive search for CH3D. We report rotational temperatures, production rates, and mixing ratios (with respect to H2O) at heliocentric distances of 1.49 AU (2004 November) and 1.21 AU (2005 January). We highlight three principal results. (1) The mixing ratios of parent volatiles measured at 1.49 AU and …

Go to article

Revealing The Structure Of A Pre-Transitional Disk: The Case Of The Herbig F Star Sao 206462 (Hd 135344b), C A. Grady, G Schneider, M L. Sitko, G M. Williger, K Hamaguchi, Sean D. Brittain, K Ablordeppey, D Apai, L Beerman, W J. Carpenter Jul 2009

Revealing The Structure Of A Pre-Transitional Disk: The Case Of The Herbig F Star Sao 206462 (Hd 135344b), C A. Grady, G Schneider, M L. Sitko, G M. Williger, K Hamaguchi, Sean D. Brittain, K Ablordeppey, D Apai, L Beerman, W J. Carpenter

Publications

SAO 206462 (HD 135344B) has previously been identified as a Herbig F star with a circumstellar disk with a dip in its infrared excess near 10 mum. In combination with a low accretion rate estimated from Br gamma, it may represent a gapped, but otherwise primordial or "pre-transitional" disk. We test this hypothesis with Hubble Space Telescope coronagraphic imagery, FUV spectroscopy and imagery and archival X-ray data, and spectral energy distribution (SED) modeling constrained by the observed system inclination, disk outer radius, and outer disk radial surface brightness (SB) profile using the Whitney Monte Carlo Radiative Transfer Code. The essentially …

Go to article

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 Jul 2009

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 …

Go to article

Section Abstracts: Astronomy, Mathematics, And Physics & Materials Science Jul 2009

Section Abstracts: Astronomy, Mathematics, And Physics & Materials Science

Virginia Journal of Science

Abstracts of the Astronomy, Mathematics and Physics & Materials Science Section for the 87th Annual Meeting of the Virginia Academy of Science, May 27-29, 2009, Virginia Commonwealth University, Richmond VA.

Go to article

A Near-Infrared Spectroscopic Survey Of Cool White Dwarfs In The Sloan Digital Sky Survey, Mukremin Kilic, Piotr M. Kowalski, Ted Von Hippel Jul 2009

A Near-Infrared Spectroscopic Survey Of Cool White Dwarfs In The Sloan Digital Sky Survey, Mukremin Kilic, Piotr M. Kowalski, Ted Von Hippel

Publications

We present near-infrared photometric observations of 15 and spectroscopic observations of 38 cool white dwarfs (WDs). This is the largest near-infrared spectroscopic survey of cool WDs to date. Combining the Sloan Digital Sky Survey photometry and our near-infrared data, we perform a detailed model atmosphere analysis. The spectral energy distributions of our objects are explained fairly well by model atmospheres with temperatures ranging from 6300 K down to 4200 K. Two WDs show significant absorption in the infrared, and are best explained with mixed H/He atmosphere models. Based on the up-to-date model atmosphere calculations by Kowalski & Saumon, we find …

Go to article

A Third Giant Planet Orbiting Hip 14810, Jason T. Wright, Debra A. Fischer, Eric B. Ford, Dimitri Veras, Ji Wang, Gregory W. Henry, Geoffrey W. Marcy, Andrew W. Howard, John Asher Johnson Jun 2009

A Third Giant Planet Orbiting Hip 14810, Jason T. Wright, Debra A. Fischer, Eric B. Ford, Dimitri Veras, Ji Wang, Gregory W. Henry, Geoffrey W. Marcy, Andrew W. Howard, John Asher Johnson

Information Systems and Engineering Management Research Publications

We present new precision radial velocities and a three-planet Keplerian orbit fit for the V = 8.5, G5 V star HIP 14810. We began observing this star at Keck Observatory as part of the N2K Planet Search Project. Wright et al. announced the inner two planets to this system, and subsequent observations have revealed the outer planet and the proper orbital solution for the middle planet. The planets have minimum masses of 3.9, 1.3, and 0.6 MJup and orbital periods of 6.67, 147.7, and 952 day, respectively. We have numerically integrated the family of orbital solutions consistent with the data …

Go to article

A First Attempt To Calibrate The Baryonic Tully-Fisher Relation With Gas-Dominated Galaxies, Stacy S. Mcgaugh Jun 2009

A First Attempt To Calibrate The Baryonic Tully-Fisher Relation With Gas-Dominated Galaxies, Stacy S. Mcgaugh

Faculty Scholarship

We calibrate the baryonic Tully-Fisher (BTF) relation using a sample of gas-dominated galaxies. These determine the absolute scale of the baryonic mass-rotation speed relation independent of the choice of stellar mass estimator. We find a BTF slope of 3.94±0.07 (random) 0.08 (systematic) and a zero point of 1.79±0.26 (random) ±0.25 (systematic). We apply this relation to estimate the stellar masses of star-dominated galaxies. This procedure reproduces the trend of mass-to-light ratio with color predicted by population synthesis models. The normalization is also correct, consistent with empirical estimates of the initial mass function used in such models.

Go to article

The Activity And Variability Of The Sun And Sun-Like Stars. Ii. Contemporaneous Photometry And Spectroscopy Of Bright Solar Analogs, Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood, Brian A. Skiff, Steven H. Saar Jun 2009

The Activity And Variability Of The Sun And Sun-Like Stars. Ii. Contemporaneous Photometry And Spectroscopy Of Bright Solar Analogs, Jeffrey C. Hall, Gregory W. Henry, G. Wesley Lockwood, Brian A. Skiff, Steven H. Saar

Information Systems and Engineering Management Research Publications

We present 14 years of contemporaneous photometric and spectroscopic observations of 28 solar analog stars, taken with the Tennessee State University Automatic Photometric Telescopes at Fairborn Observatory and the Solar-Stellar Spectrograph at Lowell Observatory. These are the best observed and most nearly Sun-like of the targets in our magnitude-limited (V ⩽  7.5) sample. The correlations between luminosity and activity reveal the expected inverse activity–brightness correlations for active stars. Strong direct correlations between activity and brightness are not prevalent for the less active solar age stars, but are precision limited. The Sun does not appear to have unusually low photometric variability …

Go to article

The Ionization Balance Of A Non-Equilibrium Plasma, Gary J. Ferland Jun 2009

The Ionization Balance Of A Non-Equilibrium Plasma, Gary J. Ferland

Physics and Astronomy Faculty Publications

Commentary on: Arnaud M. and Rothenflug R., 1985, A&AS, 60, 425.

Go to article

Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo's S5 Data, 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 Jun 2009

Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo's S5 Data, 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 have searched for gravitational waves from coalescing low mass compact binary systems with a total mass between 2M and 35 and a minimum component mass of 1M using data from the first year of the fifth science run of the three LIGO detectors, operating at design sensitivity. Depending on the mass, we are sensitive to coalescences as far as 150Mpc from the Earth. No gravitational-wave signals were observed above the expected background. Assuming a population of compact binary objects with a Gaussian mass distribution representing binary neutron star systems, black hole-neutron star binary systems, and binary black hole systems, …

Go to article

The First Two Transient Supersoft X-Ray Sources In M31 Globular Clusters And The Connection To Classical Novae, M. Henze, W. Pietsch, F. Haberl, G. Sala, R. Quimby, M. Hernanz, M. Della Valle, P. Milne, G. G. Williams, V Burwitz, J Greiner, H Stiele, Dieter H. Hartmann, A.K.H. Dong, K Hornoch Jun 2009

The First Two Transient Supersoft X-Ray Sources In M31 Globular Clusters And The Connection To Classical Novae, M. Henze, W. Pietsch, F. Haberl, G. Sala, R. Quimby, M. Hernanz, M. Della Valle, P. Milne, G. G. Williams, V Burwitz, J Greiner, H Stiele, Dieter H. Hartmann, A.K.H. Dong, K Hornoch

Publications

Context. Classical novae (CNe) have been found to represent the major class of supersoft X-ray sources (SSSs) in our neighbour galaxy M 31. Aims. We determine the properties and evolution of the two first SSSs ever discovered in the M 31 globular cluster (GC) system. Methods. We have used XMM-Newton, Chandra and Swift observations of the centre region of M 31 to discover both SSSs and to determine their X-ray light curves and spectra. We performed detailed analysis of XMM-Newton EPIC PN spectra of the source in Bol 111 (SS1) using blackbody and NLTE white dwarf (WD) atmosphere models. For …

Go to article

Chandra And Swift Observations Of The Quasi-Persistent Neutron Star Transient Exo 0748-676 Back To Quiescence, N. Degenaar, R. Wijnands, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown Jun 2009

Chandra And Swift Observations Of The Quasi-Persistent Neutron Star Transient Exo 0748-676 Back To Quiescence, N. Degenaar, R. Wijnands, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown

Physics and Astronomy Faculty Research Publications

The quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 recently started the transition to quiescence following an accretion outburst that lasted more than 24 years. We report on two Chandra and 12 Swift observations performed within five months after the end of the outburst. The Chandra spectrum is composed of a soft, thermal component that fits to a neutron star atmosphere model with kT∞ ~ 0.12keV, joined by a hard power-law tail that contributes ~20 per cent of the total 0.5-10 keV unabsorbed flux. The combined Chandra/Swift data set reveals a relatively hot and luminous quiescent system …

Go to article

Observation Of Extended Very High Energy Emission From The Supernova Remnant Ic 443 With Veritas, P. T. Reynolds, Et Al Jun 2009

Observation Of Extended Very High Energy Emission From The Supernova Remnant Ic 443 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hr during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (σ) before trials and 7.5σ after trials in a point-source search. The emission is centered at 6h16m51s + …

Go to article

Detection Of The Bl Lacertae Object H1426+428 At Tev Gamma-Ray Energies, P. T. Reynolds, Et. Al. Jun 2009

Detection Of The Bl Lacertae Object H1426+428 At Tev Gamma-Ray Energies, P. T. Reynolds, Et. Al.

Physical Sciences Publications

A very high energy γ-ray signal has been detected at the 5.5 σ level from H1426+428, an X-ray-selected BL Lacertae object at a redshift of 0.129. The object was monitored from 1995 to 1998 with the Whipple 10 m imaging atmospheric Cerenkov telescope as part of a general blazar survey; the results of these observations, although not statistically significant, were consistently positive. X-ray observations of H1426+428 during 1999 with the BeppoSAX instrument revealed that the peak of its synchrotron spectrum occurs at greater than 100 keV, leading to the prediction of observable TeV emission from this object. H1426+428 was monitored …

Go to article

Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo’S S5 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone Jun 2009

Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo’S S5 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We have searched for gravitational waves from coalescing low mass compact binary systems with a total mass between 2M⊙ and 35M⊙ and a minimum component mass of 1M⊙ using data from the first year of the fifth science run of the three LIGO detectors, operating at design sensitivity. Depending on the mass, we are sensitive to coalescences as far as 150 Mpc from the Earth. No gravitational-wave signals were observed above the expected background. Assuming a population of compact binary objects with a Gaussian mass distribution representing binary neutron star systems, black hole–neutron star binary systems, and binary black hole …

Go to article

The Onset Of Warps In Spitzer Observations Of Edge-On Spiral Galaxies., Kanak Saha, Roelof De Jong, Benne W. Holwerda Jun 2009

The Onset Of Warps In Spitzer Observations Of Edge-On Spiral Galaxies., Kanak Saha, Roelof De Jong, Benne W. Holwerda

Faculty and Staff Scholarship

We analyse warps in the nearby edge-on spiral galaxies observed in the Spitzer/Infrared Array Camera (IRAC )4.5-μm band. In our sample of 24 galaxies, we find evidence of warp in 14 galaxies. We estimate the observed onset radii for the warps in a subsample of 10 galaxies. The dark matter distribution in each of these galaxies are calculated using the mass distribution derived from the observed light distribution and the observed rotation curves. The theoretical predictions of the onset radii for the warps are then derived by applying a self-consistent linear response theory to the obtained mass models for six …

Go to article

Timing Of Substorm-Associated Auroral Oscillations, P Martin, Niescja E. Turner, J Wanliss May 2009

Timing Of Substorm-Associated Auroral Oscillations, P Martin, Niescja E. Turner, J Wanliss

Physics and Astronomy Faculty Research

Previous studies have shown that auroral luminosity oscillations are often associated with substorms. Here we examine photometer data for the magnetospheric substorm on April 1, 2000 (expansive phase onset at 0525 UT) to study the detailed timing of the auroral oscillations relative to onset. Accurate timing information for the periodicities in the photometer data were determined using the wavelet transform. We find that the oscillations occur primarily during the recovery phase. Copyright © The Society of Geomagnetism and Earth

Go to article

Proper Motions And Brightness Variations Of Nonthermal X-Ray Filaments In The Cassiopeia A Supernova Remnant, Daniel J. Patnaude, Robert A. Fesen May 2009

Proper Motions And Brightness Variations Of Nonthermal X-Ray Filaments In The Cassiopeia A Supernova Remnant, Daniel J. Patnaude, Robert A. Fesen

Dartmouth Scholarship

We present Chandra ACIS X-ray observations of the Galactic supernova remnant Cassiopeia A taken in 2007 December. Combining these data with previous archival Chandra observations taken in 2000, 2002, and 2004, we estimate the remnant's forward shock velocity at various points around the outermost shell to range between 4200 and 5200 ± 500 km s–1. Using these results together with previous analyses of Cas A's X-ray emission, we present a model for the evolution of Cas A and find that it's expansion is well fit by a ρej ∝ r –(7–9) ejecta profile running into a circumstellar …

Go to article

Sdss Unveils A Population Of Intrinsically Faint Cataclysmic Variables At The Minimum Orbital Period, B. T. Gänsicke, M. Dillon, J. Southworth, J. R. Thorstensen May 2009

Sdss Unveils A Population Of Intrinsically Faint Cataclysmic Variables At The Minimum Orbital Period, B. T. Gänsicke, M. Dillon, J. Southworth, J. R. Thorstensen

Dartmouth Scholarship

We discuss the properties of 137 cataclysmic variables (CVs) which are included in the Sloan Digital Sky Survey (SDSS) spectroscopic data base, and for which accurate orbital periods have been measured. 92 of these systems are new discoveries from SDSS and were followed-up in more detail over the past few years. 45 systems were previously identified as CVs because of the detection of optical outbursts and/or X-ray emission, and subsequently re-identified from the SDSS spectroscopy. The period distribution of the SDSS CVs differs dramatically from that of all the previously known CVs, in particular it contains a significant accumulation of …

Go to article

Old, Rich, And Eccentric: Two Jovian Planets Orbiting Evolved Metal-Rich Stars, Kathryn M. G. Peek, John Asher Johnson, Debra A. Fischer, Geoffrey W. Marcy, Gregory W. Henry, Andrew W. Howard, Jason T. Wright, Thomas B. Lowe, Sabine Reffert, Christian Schwab, Peter K. G. Williams, Howard Isaacson, Matthew J. Giguere May 2009

Old, Rich, And Eccentric: Two Jovian Planets Orbiting Evolved Metal-Rich Stars, Kathryn M. G. Peek, John Asher Johnson, Debra A. Fischer, Geoffrey W. Marcy, Gregory W. Henry, Andrew W. Howard, Jason T. Wright, Thomas B. Lowe, Sabine Reffert, Christian Schwab, Peter K. G. Williams, Howard Isaacson, Matthew J. Giguere

Information Systems and Engineering Management Research Publications

We present radial velocity measurements of two stars observed as part of the Lick Subgiants Planet Search and the Keck N2K survey. Variations in the radial velocities of both stars reveal the presence of Jupiter-mass exoplanets in highly eccentric orbits. HD 16175 is a G0 subgiant from the Lick Subgiants Planet Search, orbited by a planet having a minimum mass of 4.4 MJup, in an eccentric (e = 0.59), 2.71 yr orbit. HD 96167 is a G5 subgiant from the N2K ("Next 2000") program at Keck Observatory, orbited by a planet having a minimum mass of 0.68 MJup, in an …

Go to article

A Compton Telescope For Remote Location And Identification Of Radioactive Material, Peter F. Bloser, Jason S. Legere, Shirley M. Dame, Mark L. Mcconnell, U Bravar, James M. Ryan May 2009

A Compton Telescope For Remote Location And Identification Of Radioactive Material, Peter F. Bloser, Jason S. Legere, Shirley M. Dame, Mark L. Mcconnell, U Bravar, James M. Ryan

Space Science Center

The spare detectors from NASA's Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of gamma radiation. The gamma-ray experimental telescope assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 95 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of-flight for each coincident detection and compiles histograms of total energy and incident angle as computed using the kinematics of Compton scattering. GRETA's field of view is …

Go to article

Spitzer Observations Of The Oldest White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al. May 2009

Spitzer Observations Of The Oldest White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We present Spitzer 5-15 μm spectroscopy of one cool white dwarf and 3.6-8 μm photometry of 51 cool white dwarfs with T eff < 6000 K. The majority of our targets have accurate BVRIJHKphotometry and trigonometric parallax measurements available, which enables us to perform a detailed model atmosphere analysis using their optical, near- and mid-infrared photometry with state-of-the-art model atmospheres. We demonstrate that the optical and infrared spectral energy distributions of cool white dwarfs are well reproduced by our grid of models. Our best-fit models are consistent with the observations within 5% in all filters except the IRAC 8 μm band, which has the lowest signal-to-noise ratio photometry. Excluding …

Go to article

Mapping The Dark Side With Deimos: Globular Clusters, X-Ray Gas, And Dark Matter In The Ngc 1407 Group, Aaron J. Romanowsky, J. Strader, L. Spitler, R. Johnson, J. P. Brodie, D. A. Forbes, T. Ponman May 2009

Mapping The Dark Side With Deimos: Globular Clusters, X-Ray Gas, And Dark Matter In The Ngc 1407 Group, Aaron J. Romanowsky, J. Strader, L. Spitler, R. Johnson, J. P. Brodie, D. A. Forbes, T. Ponman

Faculty Publications

NGC 1407 is the central elliptical in a nearby evolved group of galaxies apparently destined to become a galaxy cluster core. We use the kinematics of globular clusters (GCs) to probe the dynamics and mass profile of the group's center, out to a radius of 60 kpc (~10 galaxy effective radii)—the most extended data set to date around an early-type galaxy. This sample consists of 172 GC line-of-sight velocities, most of them newly obtained using Keck/DEIMOS, with a few additional objects identified as dwarf-globular transition objects or as intragroup GCs. We find weak rotation for the outer parts of the …

Go to article

The Very Short Supersoft X-Ray State Of The Classical Nova M31n 2007-11a, M. Henze, W. Pietsch, G. Sala, M. Della Valle, M. Hernanz, J. Greiner, V. Burwitz, M. J. Freyberg, F. Haberl, Dieter H. Hartmann, P Milne, G G. Williams May 2009

The Very Short Supersoft X-Ray State Of The Classical Nova M31n 2007-11a, M. Henze, W. Pietsch, G. Sala, M. Della Valle, M. Hernanz, J. Greiner, V. Burwitz, M. J. Freyberg, F. Haberl, Dieter H. Hartmann, P Milne, G G. Williams

Publications

Context. Short supersoft X-ray source (SSS) states (durations ≤100 days) of classical novae (CNe) indicate massive white dwarfs that are candidate progenitors of supernovae type Ia. Aims. We carry out a dedicated optical and X-ray monitoring program of CNe in the bulge of M 31. Methods. We discovered M31N 2007-11a and determined its optical and X-ray light curve. We used the robotic Super-LOTIS tele-scope to obtain the optical data and XMM-Newton and Chandra observations to discover an X-ray counterpart to that nova. Results. Nova M31N 2007-11a is a very fast CN, exhibiting a very short SSS state with an appearance …

Go to article

Polarization Variability Arising From Clumps In The Winds Of Wolf-Rayet Stars., Qing-Kang Li, Joseph Cassinelli, John Brown, Richard Ignace May 2009

Polarization Variability Arising From Clumps In The Winds Of Wolf-Rayet Stars., Qing-Kang Li, Joseph Cassinelli, John Brown, Richard Ignace

ETSU Faculty Works

The polarimetric and photometric variability of Wolf-Rayet (WR) stars as caused by clumps in the winds, is revisited. In the model which is improved from Li et al. 2000, the radial expansion of the thickness is accounted for, but we retain the dependence on the beta velocity law, stellar occultation effects. We again search for parameters that can yield results consistent with observations in regards to the mean polarization, the ratio of polarimetric to photometric variability, and the volume filling factor. Clump generation and spatial distribution are randomized by the Monte Carlo method so as to produce clumps which are, …

Go to article

First Prev Next Last