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2006

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Articles 31 - 60 of 179

Full-Text Articles in Astrophysics and Astronomy

The Grb 060218/Sn 2006aj Event In The Context Of Other Gamma-Ray Burst Supernovae, P. Ferreo, D. A. Kann, A. Zeh, S. Klose, E. Pian, E. Palazzi, N. Masetti, Dieter H. Hartmann, J. Sollerman, J. Deng, A V. Filippenko, J Greiner, M A. Hughes, P Mazzali, W Li, E Rol, R J. Smith, N R. Tanvir Oct 2006

The Grb 060218/Sn 2006aj Event In The Context Of Other Gamma-Ray Burst Supernovae, P. Ferreo, D. A. Kann, A. Zeh, S. Klose, E. Pian, E. Palazzi, N. Masetti, Dieter H. Hartmann, J. Sollerman, J. Deng, A V. Filippenko, J Greiner, M A. Hughes, P Mazzali, W Li, E Rol, R J. Smith, N R. Tanvir

Publications

The supernova SN 2006aj associated with GRB 060218 is the second-closest GRB-SN observed to date (z =0.033). We present Very Large Telescope, Liverpool Telescope, and Katzman Automatic Imaging Telescope multi-color photometry of SN 2006aj. This super-nova is found to be subluminous and rapidly evolving. Its early light curve includes an additional wavelength-dependent component, which can be interpreted as shock break-out. We compare the photometric evolution of multi-band light curves with the corresponding properties of the present sample of more than 10 GRB-SNe with precisely known redshifts. Using host-galaxy extinction measure-ments, we derive extinction-corrected GRB-SN luminosities and place SN 2006aj in …

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Minutes: Council Meeting Oct 2006

Minutes: Council Meeting

Virginia Journal of Science

Minutes of the VAS Council meeting Friday May 26, 2006, 8 - 9:40 AM, at Skelton Conference Center Inn, Virginia Tech, Blacksburg VA. Minutes were edited for publication.

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Random Flows And Diagnostics Of Turbulence In The High Latitude Cirrus, Steven N. Shore, Ted N. Larosa, Raymond J. Chastain, Loris Magnani Oct 2006

Random Flows And Diagnostics Of Turbulence In The High Latitude Cirrus, Steven N. Shore, Ted N. Larosa, Raymond J. Chastain, Loris Magnani

Faculty Articles

Aims: We present an analysis of the exceptionally turbulent velocity field in the high Galactic latitude cirrus cloud MBM 3. As in the other translucent clouds in our study (MBM 16 and MBM 40), there is no evidence for internal star formation. However, the large scale velocity variation in this cloud is more pronounced. Methods: We have mapped the cloud in 12CO and 13CO (1-0) at high spatial (0.03 pc) and velocity (0.06 km s-1) resolution. We constructed several velocity probability density functions (PDFs), estimated the turbulent transfer rate, and analyzed the linewidths as a function of the size of …

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Cluster Observations Of Reconnection Due To The Kelvin-Helmholtz Instability At The Dawnside Magnetospheric Flank, K. Nykyri, A. Otto, B. Lavraud, C. Mouikis, L. M. Kistler, A. Balogh, H. Rème Oct 2006

Cluster Observations Of Reconnection Due To The Kelvin-Helmholtz Instability At The Dawnside Magnetospheric Flank, K. Nykyri, A. Otto, B. Lavraud, C. Mouikis, L. M. Kistler, A. Balogh, H. Rème

Publications

On 3 July 2001, the four Cluster satellites traversed along the dawnside magnetospheric flank and observed large variations in all plasma parameters. The estimated magnetopause boundary normals were oscillating in the z-direction and the normal component of the magnetic field showed systematic ~2–3 min bipolar variations for 1 h when the IMF had a small positive bz-component and a Parker-spiral orientation in the x, y-plane. Brief ~33 s intervals with excellent deHoffman Teller frames were observed satisfying the Wal´en relation. Detailed comparisons with 2- D MHD simulations indicate that Cluster encountered rotational discontinuities generated by Kelvin-Helmholtz instability. We estimate a …

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Hd 131861, A Double-Line Spectroscopic Triple System, Francis C. Fekel, Gregory W. Henry, David J. Barlow, Dimitri Pourbaix Sep 2006

Hd 131861, A Double-Line Spectroscopic Triple System, Francis C. Fekel, Gregory W. Henry, David J. Barlow, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

Our red-wavelength spectroscopic observations of HD 131861, a previously known single-line multiple system, span 20 years. Now lines of two components, the short-period F5 V primary and G8 V secondary, have been detected. The inner orbit is circular with a period of 3.5507439 days, while the outer orbit of the system has a period of 1642 days or 4.496 yr and a relatively low eccentricity of 0.10. Analysis of the Hipparcos data produces a well-determined astrometric orbit for the long-period system that has an inclination of 52°. Our photometric observations show shallow primary and secondary eclipses of the short-period pair, …

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Neutrino Oscillation Effects On Supernova Light Element Synthesis, Takashi Yoshida, Toshitaka Kajino, Hidekazu Yokomakura, Keichi Kimura, Akira Takamura, Dieter H. Hartmann Sep 2006

Neutrino Oscillation Effects On Supernova Light Element Synthesis, Takashi Yoshida, Toshitaka Kajino, Hidekazu Yokomakura, Keichi Kimura, Akira Takamura, Dieter H. Hartmann

Publications

Neutrion oscillations affect light-element synthesis through the v-process in supernova explosions. The 7Li and 11B yields produced in a supernova explosion of a 16.2 M ⊙ star model increase by factors of 1.9 and 1.3 in the case of the large mixing angle solution with a normal mass hierarchy of sin^2 2θ13 >~ 2x10^-3 compared with those without the oscillations. In the case of an inerted mass hierarchy or a nonadiabatic 1-3 mixing resonance, the increment of their yields is much smaller. Neutrino oscillations raise the reaction rates of charged-current v-process reactions in the region outside oxygen-rich layers. The number …

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Heavy-Ion Elemental Abundances In Large Solar Energetic Particle Events And Their Implications For The Seed Population, Mihir I. Desai, Glenn M. Mason, Robert E. Gold, Stamatios M. Krimigis, Christina M.S. Cohen, Richard A. Mewaldt, Joseph E. Mazur, Joseph R. Dwyer Sep 2006

Heavy-Ion Elemental Abundances In Large Solar Energetic Particle Events And Their Implications For The Seed Population, Mihir I. Desai, Glenn M. Mason, Robert E. Gold, Stamatios M. Krimigis, Christina M.S. Cohen, Richard A. Mewaldt, Joseph E. Mazur, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed the ∼0.1-10 MeV nucleonˉ¹ abundances of heavy ions from ³He through Fe in 64 large solar energetic particle (LSEP) events observed on board the Advanced Composition Explorer from 1997 November through 2005 January. Our main results are (1) the 0.5-2.0 MeV nucleonˉ¹ ³He/⁴He ratio is enhanced between factors of ∼2-150 over the solar wind value in 29 (∼46%) events. (2) The Fe/O ratio in most LSEP events decreases with increasing energy up to ∼60 MeV nucleonˉ¹. (3) The Fe/O ratio is independent of CME speed, flare longitude, event size, the ³He/⁴He ratio, the pre-event Fe/O ratio, and …

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A Spitzer Space Telescope Study Of Sn 2002hh: An Infrared Echo From A Type Iip Supernova, W. P. S. Meikle, S. Mattila, C. L. Gerardy, R. Kotak, M. Pozzo, S. D. Van Dyk, D. Farrah, R. A. Fesen Sep 2006

A Spitzer Space Telescope Study Of Sn 2002hh: An Infrared Echo From A Type Iip Supernova, W. P. S. Meikle, S. Mattila, C. L. Gerardy, R. Kotak, M. Pozzo, S. D. Van Dyk, D. Farrah, R. A. Fesen

Dartmouth Scholarship

We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, …

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Comparison Of Tropospheric Ozone Columns Calculated From Mls, Omi, And Ozonesonde Data, Gary A. Morris, Bojan Bojkov, Mark R. Schoeberl, Amy Wozniak, Jerry Ziemke, Sushil Chandra, Jack Fishman, Ivanka Stajner Sep 2006

Comparison Of Tropospheric Ozone Columns Calculated From Mls, Omi, And Ozonesonde Data, Gary A. Morris, Bojan Bojkov, Mark R. Schoeberl, Amy Wozniak, Jerry Ziemke, Sushil Chandra, Jack Fishman, Ivanka Stajner

Physics and Astronomy Faculty Presentations

This poster shows a comparison of three derived tropospheric ozone residual (TOR) products with integrated tropospheric ozone columns from ozonesonde profile: (1) the method of Ziemke et al. (2006), (2) a modified version of Fishman et al. (2003), and (3) a trajectory mapping approach. In each case, MLS ozone profiles are integrated to the tropopause and subtracted from OMI (TOMS retrieval) total column ozone. The effectiveness of each of these techniques is examined as a function of latitude, time, and geographic region. In general, we find good agreement between the derived products and the ozonesondes, with the Fishman et al. …

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The First Extrasolar Planet Discovered With A New-Generation High-Throughput Doppler Instrument, Jian Ge, Julian C. Van Eyken, Suvrath Mahadevan, Curtis Dewitt, Stephen R. Kane, Roger Cohen, Andrew Vanden Heuvel, Scott W. Fleming, Pengcheng Guo, Gregory W. Henry, Donald P. Schneider, Lawrence W. Ramsey, Robert A. Wittenmyer, Michael Endl, William D. Cochran, Eric B. Ford, Eduardo L. Martín, Garik Israelian, Jeff A. Valenti, David Montes Sep 2006

The First Extrasolar Planet Discovered With A New-Generation High-Throughput Doppler Instrument, Jian Ge, Julian C. Van Eyken, Suvrath Mahadevan, Curtis Dewitt, Stephen R. Kane, Roger Cohen, Andrew Vanden Heuvel, Scott W. Fleming, Pengcheng Guo, Gregory W. Henry, Donald P. Schneider, Lawrence W. Ramsey, Robert A. Wittenmyer, Michael Endl, William D. Cochran, Eric B. Ford, Eduardo L. Martín, Garik Israelian, Jeff A. Valenti, David Montes

Information Systems and Engineering Management Research Publications

We report the detection of the first extrasolar planet, ET-1 (HD 102195b), using the Exoplanet Tracker (ET), a new-generation Doppler instrument. The planet orbits HD 102195, a young star with solar metallicity that may be part of the local association. The planet imparts radial velocity variability to the star with a semiamplitude of 63.4 ± 2.0 m s-1 and a period of 4.11 days. The planetary minimum mass (m sin i) is 0.488MJ ± 0.015MJ. The planet was initially detected in the spring of 2005 with the Kitt Peak National Observatory (KPNO) 0.9 m coudé feed telescope. The detection was …

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The Effect Of Porosity On X-Ray Emission-Line Profiles From Hot-Star Winds, S. P. Owocki, David H. Cohen Sep 2006

The Effect Of Porosity On X-Ray Emission-Line Profiles From Hot-Star Winds, S. P. Owocki, David H. Cohen

Physics & Astronomy Faculty Works

We investigate the degree to which the nearly symmetric form of X- ray emission lines seen in Chandra spectra of early- type supergiant stars could be explained by the possibly porous nature of their spatially structured stellar winds. Such porosity could effectively reduce the bound- free absorption of X- rays emitted by embedded wind shocks, and thus allow a more similar transmission of redshifted and blueshifted emission from the back and front hemispheres, respectively. To obtain the localized self- shielding that is central to this porosity effect, it is necessary that the individual clumps be optically thick. In a medium …

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Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., Richard Ignace, A. Brimeyer Sep 2006

Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., Richard Ignace, A. Brimeyer

ETSU Faculty Works

A number of strong infrared forbidden lines have been observed in several evolved Wolf–Rayet (WR) star winds, and these are important for deriving metal abundances and testing stellar evolution models. In addition, because these optically thin lines form at large radius in the wind, their resolved profiles carry an imprint of the asymptotic structure of the wind flow. This work presents model forbidden line profile shapes formed in axisymmetric winds. It is well known that an optically thin emission line formed in a spherical wind expanding at constant velocity yields a flat-topped emission profile shape. Simulated forbidden lines are produced …

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Detection Of A Far-Infrared Bow Shock Nebula Around R Hya: The First Miriad Results, T. Ueta, A. K. Speck, R. E. Stencel, F. Herwig, R. D. Gehrz, R. Szczerba, H. Izumiura, A. A. Zijlstra, W. B. Latter, M. Matsuura, M. Meixner, M. Steffen, Moshe Elitzur Sep 2006

Detection Of A Far-Infrared Bow Shock Nebula Around R Hya: The First Miriad Results, T. Ueta, A. K. Speck, R. E. Stencel, F. Herwig, R. D. Gehrz, R. Szczerba, H. Izumiura, A. A. Zijlstra, W. B. Latter, M. Matsuura, M. Meixner, M. Steffen, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present the first results of the MIRIAD (MIPS InfraRed Imaging of AGB Dust shells) project using the Spitzer Space Telescope. The primary aim of the project is to probe the material distribution in the extended circumstellar envelopes (CSEs) of evolved stars and recover the fossil record of their mass-loss history. Hence, we must map the whole of the CSEs plus the surrounding sky for background subtraction while avoiding the central star that is brighter than the detector saturation limit. With our unique mapping strategy, we have achieved better than 1 MJy sr-1 sensitivity in 3 hr of …

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Energy Levels And Transition Probabilities For Boron-Like Fe Xxii, V. Jonauskas, P. Bogdanovich, F. P. Keenan, R. Kisielius, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, P. H. Norrington Sep 2006

Energy Levels And Transition Probabilities For Boron-Like Fe Xxii, V. Jonauskas, P. Bogdanovich, F. P. Keenan, R. Kisielius, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, P. H. Norrington

Physics and Astronomy Faculty Publications

The Multiconfiguration Dirac-Fock method is used to calculate the energies of the 407 lowest levels in FeXXII. These results are cross-checked using a suite of codes which employ the configuration interaction method on the basis set of transformed radial orbitals with variable parameters, and takes into account relativistic corrections in the Breit-Pauli approximation. Transition probabilities, oscillator and line strengths are presented for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transitions among these levels. The total radiative transition probabilities, as well as the five largest values from each level be it of E1, M1, E2, M2, or E3 …

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1021-0304_Mir_Irs, Michael C. Cushing Sep 2006

1021-0304_Mir_Irs, Michael C. Cushing

Publications and Research

No abstract provided.

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Fourier Spectroscopy Of Ultrashort Laser Pulses, Scott D. Bergeson, Justin Peatross Sep 2006

Fourier Spectroscopy Of Ultrashort Laser Pulses, Scott D. Bergeson, Justin Peatross

Faculty Publications

We describe a Fourier-transform spectrometer appropriate for use in an undergraduate optics laboratory. The modular design, which uses off-the-shelf equipment, is suitable for determining the spectra of ultrashort pulsed and continuous light sources. The spectrometer does not require equal step sizes for the motion of the mirror. An algorithm interpolates the phase of both a reference and an unknown light beam at equal intervals before performing the Fourier transform. The interferometer scan and the phase and spectral analysis are performed in a few seconds, making the apparatus a useful tool for teaching concepts of temporal coherence and Fourier spectroscopy.

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Hr 1613: A Slowly Rotating A Dwarf Spectroscopic Binary With Solar Abundances, Francis C. Fekel, Michael H. Williamson, Christiane Buggs, Gerald Onuoha, Brittany Smith Aug 2006

Hr 1613: A Slowly Rotating A Dwarf Spectroscopic Binary With Solar Abundances, Francis C. Fekel, Michael H. Williamson, Christiane Buggs, Gerald Onuoha, Brittany Smith

Information Systems and Engineering Management Research Publications

From two sets of radial velocities we have obtained the orbital elements of HR 1613. This single-lined binary has an orbital period of 8.11128 days and a nearly circular orbit. The primary has an A9 V spectral type and a v sin i value of 11 km s-1, while the unseen secondary is likely a K or M dwarf. Spectral classifications and spectrum synthesis analysis indicate that the abundances of the primary are normal. We reject the possibility that the primary of HR 1613 is seen nearly pole-on and instead argue that its rotational inclination is at least 20°, resulting …

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Characterization Of Single-Sided Charge-Sharing Czt Strip Detectors For Gamma-Ray Astronomy, B Donmez, John R. Macri, James M. Ryan, Jason S. Legere, Mark L. Mcconnell, Mark Widholm, T Narita, L A. Hamel Aug 2006

Characterization Of Single-Sided Charge-Sharing Czt Strip Detectors For Gamma-Ray Astronomy, B Donmez, John R. Macri, James M. Ryan, Jason S. Legere, Mark L. Mcconnell, Mark Widholm, T Narita, L A. Hamel

Space Science Center

We report progress in the study of thick single-sided charge-sharing cadmium zinc telluride (CZT) strip detector modules designed to perform spectroscopy and 3-D imaging of gamma-rays. We report laboratory measurements including spectroscopy, efficiency and 3-D imaging capability of prototype detectors (15 × 15 × 7.5mm3) with 11×11 unit cells. We also report on Monte Carlo simulations (GEANT4 v7.1) to investigate the effect of multihits on detector performance in both spectroscopy and imaging. We compare simulation results with data obtained from laboratory measurements and discuss the implications for future strip detector designs.

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Sound Absorption And Sound Power Measurements In Reverberation Chambers Using Energy Density Methods, David B. Nutter Aug 2006

Sound Absorption And Sound Power Measurements In Reverberation Chambers Using Energy Density Methods, David B. Nutter

Theses and Dissertations

Measurements in a reverberation chamber use spatially averaged squared pressure to calculate sound absorption, sound power, and other sound measurements. While a reverberation chamber provides an approximation of a diffuse sound field, variations in the measurements introduce uncertainty in measurement results. Room qualification procedures require a sufficient number of source-receiver locations to obtain suitable measurements. The total acoustic energy density provides greater spatial uniformity than squared pressure, which requires fewer source-receiver positions to produce similar or better accuracy in measurement results. This paper explores the possibility of using energy density in place of squared pressure, using methods outlined in current …

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Heliospheric Response To Different Possible Interstellar Environments, Hans-Reinhard Muller, Priscilla C. Frisch, Vladimir Florinski, Gary P. Zank Aug 2006

Heliospheric Response To Different Possible Interstellar Environments, Hans-Reinhard Muller, Priscilla C. Frisch, Vladimir Florinski, Gary P. Zank

Dartmouth Scholarship

At present, the heliosphere is embedded in a warm, low-density interstellar cloud that belongs to a cloud system flowing through the local standard of rest with a velocity near ~18 km s-1. The velocity structure of the nearest interstellar material (ISM), combined with theoretical models of the local interstellar cloud (LIC), suggest that the Sun passes through cloudlets on timescales of ≤103-104 yr, so the heliosphere has been, and will be, exposed to different interstellar environments over time. By means of a multifluid model that treats plasma and neutral hydrogen self-consistently, the interaction of the …

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Spinning-Black-Hole Binaries: The Orbital Hang-Up, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower Aug 2006

Spinning-Black-Hole Binaries: The Orbital Hang-Up, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower

Physics & Astronomy Faculty Publications

We present the first fully-nonlinear numerical study of the dynamics of highly-spinning-black-hole binaries. We evolve binaries from quasicircular orbits (as inferred from post-Newtonian theory), and find that the last stages of the orbital motion of black-hole binaries are profoundly affected by their individual spins. In order to cleanly display its effects, we consider two equal-mass holes with individual spin parameters S/m2=0.757, both aligned and antialigned with the orbital angular momentum (and compare with the spinless case), and with an initial orbital period of 125M. We find that the aligned case completes three orbits and merges significantly after the antialigned case, …

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Feedback Applications In Active Noise Control For Small Axial Cooling Fans, Matthew J. Green Aug 2006

Feedback Applications In Active Noise Control For Small Axial Cooling Fans, Matthew J. Green

Theses and Dissertations

Feedback active noise control (ANC) has been applied as a means of attenuating broadband noise from a small axial cooling fan. Such fans are used to maintain thermal stability inside of computers, projectors, and other office equipment and home appliances. The type of low-level noise radiated from axial cooling fans has been classified as harmful to productivity and human well being. Previous research has successfully implemented feed-forward ANC, targeting specific narrow-band fan noise content related to the blade passage frequency (BPF) of the fan. The reference signal required for a feed-forward algorithm limits its ability to attenuate much of the …

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Linda French, Willis Kern Aug 2006

Linda French, Willis Kern

Interviews for WGLT

Willis Kern interviews Associate Professor of Physics Linda French about her involvement on an advisory panel regarding Pluto's status as a planet. (requires RealPlayer)

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Signals For Lorentz Violation In Post-Newtonian Gravity, Quentin G. Bailey, V. Alan Kostelecký Aug 2006

Signals For Lorentz Violation In Post-Newtonian Gravity, Quentin G. Bailey, V. Alan Kostelecký

Publications

The pure-gravity sector of the minimal standard-model extension is studied in the limit of Riemann spacetime. A method is developed to extract the modified Einstein field equations in the limit of small metric fluctuations about the Minkowski vacuum, while allowing for the dynamics of the 20 independent coefficients for Lorentz violation. The linearized effective equations are solved to obtain the post-Newtonian metric. The corresponding post-Newtonian behavior of a perfect fluid is studied and applied to the gravitating many-body system. Illustrative examples of the methodology are provided using bumblebee models. The implications of the general theoretical results are studied for a …

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Mesoscopic Domain Average Engineering Simulations Of Ferroelectric Perovskites Compared With Multidomain Group Theoretical Predictions, Brandon J. Keith, Dorian M. Hatch Aug 2006

Mesoscopic Domain Average Engineering Simulations Of Ferroelectric Perovskites Compared With Multidomain Group Theoretical Predictions, Brandon J. Keith, Dorian M. Hatch

Faculty Publications

Engineered, multidomain ferroelectrics are of current interest for mechatronic and optical applications. Previously [D. M. Hatch et al., J. Appl. Phys. 94, 5220 (2003)], we presented a set of tables/symmetry rules showing all possible domain average engineered multidomain structures arising from [100]-, [110]-, and [111]-ordering ferroelectric transitions from a Pm[overline 3]m perovskite structure. In this work we test those predictions against three-dimensional mesoscopic fast quench simulations under various electric/stress field combinations and find excellent agreement with multidomain group theory. These simulations use a Langevin strain-displacement/polarization evolution strategy and are important to developing processing conditions for materials with precise domain structures.

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Understanding Dc-Bias Sputtered Thorium Oxide Thin Films Useful In Euv Optics, William R. Evans, Sarah C. Barton, Michael Clemens, David D. Allred Aug 2006

Understanding Dc-Bias Sputtered Thorium Oxide Thin Films Useful In Euv Optics, William R. Evans, Sarah C. Barton, Michael Clemens, David D. Allred

Faculty Publications

We use spectroscopic ellipsometry to determine the optical constants of seven thin-film ThO2 samples deposited by radio-frequency sputtering, thickness ranging between 24 and 578 nm, for the spectral range of 1.2 to 6.5. We used a hollow-cathode light source and vacuum monochromator to measure constants at 10.2 eV. None of the deposition parameters studied including DC-bias voltages successfully increased the n of (that is, densify) thoria films. The value of n at 3.0 eV is 1.86 ± 0.04. We find compelling evidence to conclude that the direct bad gap is at ~5.9 eV, clarifying the results of others, some of …

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The N2k Consortium. Vi. Doppler Shifts Without Templates And Three New Short-Period Planets, John Asher Johnson, Geoffrey W. Marcy, Debra A. Fischer, Gregory Laughlin, R. Paul Butler, Gregory W. Henry, Jeff A. Valenti, Eric B. Ford, Steve Vogt, Jason T. Wright Aug 2006

The N2k Consortium. Vi. Doppler Shifts Without Templates And Three New Short-Period Planets, John Asher Johnson, Geoffrey W. Marcy, Debra A. Fischer, Gregory Laughlin, R. Paul Butler, Gregory W. Henry, Jeff A. Valenti, Eric B. Ford, Steve Vogt, Jason T. Wright

Information Systems and Engineering Management Research Publications

We present a modification to the iodine cell Doppler technique that eliminates the need for an observed stellar template spectrum. For a given target star, we iterate toward a synthetic template spectrum beginning with an existing template of a similar star. We then perturb the shape of this first-guess template to match the program observation of the target star taken through an iodine cell. The elimination of a separate template observation saves valuable telescope time, a feature that is ideally suited for the quick-look strategy employed by the "Next 2000 Stars" (N2K) planet search program. Tests using Keck HIRES (High …

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The Role Of Interplanetary Scattering In Western Hemisphere Large Solar Energetic Particle Events, Glenn M. Mason, Mihir I. Desai, Christina M.S. Cohen, Richard A. Mewaldt, Edward C. Stone, Joseph R. Dwyer Aug 2006

The Role Of Interplanetary Scattering In Western Hemisphere Large Solar Energetic Particle Events, Glenn M. Mason, Mihir I. Desai, Christina M.S. Cohen, Richard A. Mewaldt, Edward C. Stone, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

Using high-sensitivity instruments on the ACE spacecraft, we have examined the intensities of O and Fe in 14 large solar energetic particleevents whose parent activity was in the solar western hemisphere. Sampling the intensities at low (∼273 keV nucleonˉ¹) and high (∼12 MeV nucleonˉ¹) energies, we find that at the same kinetic energy per nucleon, the Fe/O ratio decreases with time, as has been reported previously. This behavior is seen in more than 70% of the cases during the rise to maximum intensity and continues in most cases into the decay phase. We find that for most events if we …

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Determining The H+ Region / Pdr Equation Of State In Star-Forming Regions, N. P. Abel, Gary J. Ferland Aug 2006

Determining The H+ Region / Pdr Equation Of State In Star-Forming Regions, N. P. Abel, Gary J. Ferland

Physics and Astronomy Faculty Publications

The emission-line regions of starburst galaxies and active nuclei reveal a wealth of spectroscopic information. A unified picture of the relationship among ionized, atomic, and molecular gas makes it possible to better understand these observations. We performed a series of calculations designed to determine the equation of state-the relationship among density, temperature, and pressure-through emission-line diagnostic ratios that form in the H+ region and the photodissociation region (PDR). We consider a wide range of physical conditions in the H+ region. We connect the H+ region to the PDR by considering two constant pressure cases: one with no …

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Whole Earth Telescope Observations Of The Pulsating Subdwarf B Star Pg 0014+067, Maja Vučković, Matt A. Wood, V. Wilkat Aug 2006

Whole Earth Telescope Observations Of The Pulsating Subdwarf B Star Pg 0014+067, Maja Vučković, Matt A. Wood, V. Wilkat

Aerospace, Physics, and Space Science Faculty Publications

PG 0014+067 is one of the most promising pulsating subdwarf B stars for seismic analysis, as it has a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental challenge to understanding the pulsations of these stars, as the mode density is too complex to be explained only with radial and nonradial low-degree (l < 3) p-modes without rotational splittings. One proposed solution, suggested by Brassard et al. in 2001 for the case of PG 0014+067 in particular, assigns some modes with high degree (l - 3). On the other hand, theoretical models of sdB stars suggest that they may retain rapidly rotating cores, and so the high mode density may result from the presence of a few rotationally split triplet (l = 1) and quintuplet (l = 2) modes, along with radial (l = 0)p-modes. To examine alternative theoretical models for these stars, we need better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope for two weeks in 2004 October. In this paper we report the results of Whole Earth Telescope observations of the pulsating subdwarf B star PG 0014+067. We find that the frequencies seen in PG 0014+067 do not appear to fit any theoretical model currently available; however, we find a simple empirical relation that is able to match all of the well-determined frequencies in this star.

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