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Articles 7081 - 7110 of 8870

Full-Text Articles in Astrophysics and Astronomy

Α-Enhanced Integrated Lick/Ids Spectral Indices And Milky Way And M31 Globular Clusters And Early-Type Galaxies, Hyun Chul Lee, Guy Worthey Sep 2005

Α-Enhanced Integrated Lick/Ids Spectral Indices And Milky Way And M31 Globular Clusters And Early-Type Galaxies, Hyun Chul Lee, Guy Worthey

Physics & Astronomy Faculty Publications

All 25 Lick/IDS spectral indices have been computed for the integrated light of simple stellar populations over broad ranges of age and metallicity and with effects from horizontal-branch stars fully implemented. Our models employ α-enhanced isochrones at the sub-solar metallicity regime, but solar-scaled ones at solar and super-solar metallicity. We have also employed the updated response functions of Houdashelt et al. at the solar and super-solar metallicity regime, so that we could assess the light-element enhancement phenomena seen from metal-rich early-type galaxies. For Balmer indices a significant response was noted for Hγ and Hδ when α-elements are enhanced, but Hβ …

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Dark-Energy Evolution Across The Cosmological-Constant Boundary, Robert R. Caldwell, Michael Doran Aug 2005

Dark-Energy Evolution Across The Cosmological-Constant Boundary, Robert R. Caldwell, Michael Doran

Dartmouth Scholarship

We explore the properties of dark-energy models for which the equation of state, w, defined as the ratio of pressure to energy density, crosses the cosmological-constant boundary w=−1. We adopt an empirical approach, treating the dark energy as an uncoupled fluid or a generalized scalar field. We describe the requirements for a viable model, in terms of the equation of state and sound speed. A generalized scalar field cannot safely traverse w=−1, although a pair of scalars with w>−1 and w<−1 will work. A fluid description with a well-defined sound speed can also cross the boundary. Contrary to expectations, such a crossing model does not instantaneously resemble a cosmological constant at the moment w=−1 since the density and pressure perturbations do not necessarily vanish. But because a dark energy with w<−1 dominates only at very late times, and because the dark energy is not generally prone to gravitational clustering, then crossing the cosmological-constant boundary leaves no distinct imprint.

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Chemical Composition In The Globular Cluster M71 From Keck Hires Spectra Of Turnoff Stars, Ann Merchant Boesgaard, Jeremy R. King, Ann Marie Cody, Alex Stephens, Constantine P. Deliyannis Aug 2005

Chemical Composition In The Globular Cluster M71 From Keck Hires Spectra Of Turnoff Stars, Ann Merchant Boesgaard, Jeremy R. King, Ann Marie Cody, Alex Stephens, Constantine P. Deliyannis

Publications

We have made observations with the Keck I telescope and HIRES at a resolution of ∼45,000 of five nearly identical stars at the turn-off of the metal-rich globular cluster M 71. Our mean Fe abundance, [Fe/H]=-0.80 +-0.02, is in excellent agreement with previous cluster determinations from both giants and near-turnoff stars. There is no clear evidence for any star-to-star abundance differences or correlations in our sample. Abundance ratios of the Fe-peak elements (Cr, Ni) are similar to Fe. The turn-off stars in M71 have remarkably consistent enhancements of 0.2 - 0.3 dex in [Si/Fe], [Ca/Fe] and [Ti/Fe] -- like the …

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An Acoustical Analysis Of Domes Coupled To Rooms, With Special Application To The Darussholah Mosque, In East Java, Indonesia, Sentagi Sesotya Utami Aug 2005

An Acoustical Analysis Of Domes Coupled To Rooms, With Special Application To The Darussholah Mosque, In East Java, Indonesia, Sentagi Sesotya Utami

Theses and Dissertations

Concave surfaces are often considered to be detrimental or precarious in room acoustics, especially because of the impact they have on the distribution of sound energy. However, it is often difficult to avoid such surfaces in buildings with specific architectural functions. A primary example of this involves mosques, which are sacred places of worship for Muslims. In keeping with the Islamic architectural style, most mosques incorporate a symbolic centralized domed ceiling as part of their room structures. These domes are open on the bottom and coupled to the acoustic spaces below. In many cases, the lower spaces may be idealized …

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Chromospherically Active Stars. Xxv. Hd 144110=Ev Draconis, A Double-Lined Dwarf Binary, Francis C. Fekel, Gregory W. Henry, Ceteka Lewis Aug 2005

Chromospherically Active Stars. Xxv. Hd 144110=Ev Draconis, A Double-Lined Dwarf Binary, Francis C. Fekel, Gregory W. Henry, Ceteka Lewis

Information Systems and Engineering Management Research Publications

New spectroscopic and photometric observations of HD 144110 have been used to obtain an improved orbital element solution and determine some basic properties of the system. This chromospherically active, double-lined spectroscopic binary has an orbital period of 1.6714012 days and a circular orbit. We classify the components as G5 V and K0 V and suggest that they are slightly metal-rich. The photometric observations indicate that the rotation of HD 144110 is synchronous with the orbital period. Despite the short orbital period, no evidence of eclipses is seen in our photometry.

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Chandra Hetgs Multiphase Spectroscopy Of The Young Magnetic O Star Theta(1) Orionis C, M. Gagné, M. E. Oksala, David H. Cohen, Stephanie Korinne Tonnesen , '03, A. Ud-Doula, S. P. Owocki, R. H.D. Townsend, J. J. Macfarlane Aug 2005

Chandra Hetgs Multiphase Spectroscopy Of The Young Magnetic O Star Theta(1) Orionis C, M. Gagné, M. E. Oksala, David H. Cohen, Stephanie Korinne Tonnesen , '03, A. Ud-Doula, S. P. Owocki, R. H.D. Townsend, J. J. Macfarlane

Physics & Astronomy Faculty Works

We report on four Chandra grating observations of the oblique magnetic rotator theta(1) Ori C (O5.5 V), covering a wide range of viewing angles with respect to the star's 1060 G dipole magnetic field. We employ line-width and centroid analyses to study the dynamics of the X-ray - emitting plasma in the circumstellar environment, as well as line-ratio diagnostics to constrain the spatial location, and global spectral modeling to constrain the temperature distribution and abundances of the very hot plasma. We investigate these diagnostics as a function of viewing angle and analyze them in conjunction with new MHD simulations of …

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Beryllium Enhancement As Evidence For Accretion In A Lithium-Rich F Dwarf, Johanna F. Ashwell, R D. Jeffries, Barry Smalley, C P. Deliyannis, Aaron Steinhauer, Jeremy R. King Aug 2005

Beryllium Enhancement As Evidence For Accretion In A Lithium-Rich F Dwarf, Johanna F. Ashwell, R D. Jeffries, Barry Smalley, C P. Deliyannis, Aaron Steinhauer, Jeremy R. King

Publications

The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual pattern of photospheric abundances, including an order of magnitude enhancement of lithium and iron-peak elements, but an under-abundance of carbon. As a consequence of its thin convection zone these anomalies have been attributed to either radiative diffusion or the accretion of hydrogen-depleted material. By comparing high resolution VLT/UVES spectra of J37 (and other F stars in NGC 6633) with syntheses of the Be ii doublet region at 3131 Ang, we establish that J37 also has a Be abundance (A(Be)=3.0+/-0.5) that is at least ten times the …

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Is First J102347.6+003841 Really A Cataclysmic Binary?, John R. Thorstensen, Eve Armstrong Aug 2005

Is First J102347.6+003841 Really A Cataclysmic Binary?, John R. Thorstensen, Eve Armstrong

Dartmouth Scholarship

The radio source FIRST J102347.6+003841 was presented as the first radio-selected cataclysmic variable star. In the discovery paper, Bond et al. (2002) show a spectrum consistent with a magnetic AM Her–type system, or polar, featuring strong Balmer lines, He I and He II emission lines, and a light curve with rapid, irregular flickering. In contrast, Woudt, Warner, and Pretorius found a smoothly varying light curve with a period near 4.75 hr and one minimum per orbit, indicating that the state of the system had changed dramatically. We present time-resolved spectra showing a superficially normal, mid-G type photosphere, with no detectable …

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Measuring The Halo Mass Of Z ∼ 3 Damped Lyα Absorbers From The Absorber-Galaxy Cross-Correlation, Nicolas Bouché, Jeffrey P. Gardner, Neal Katz, David H. Weinberg, Romeel Davé, James D. Lowenthal Jul 2005

Measuring The Halo Mass Of Z ∼ 3 Damped Lyα Absorbers From The Absorber-Galaxy Cross-Correlation, Nicolas Bouché, Jeffrey P. Gardner, Neal Katz, David H. Weinberg, Romeel Davé, James D. Lowenthal

Astronomy: Faculty Publications

We test the reliability of a method to measure the mean halo mass of absorption-line systems such as damped Lyα absorbers (DLAs). The method is based on measuring the ratio of the cross-correlation between DLAs and galaxies to the autocorrelation of the galaxies themselves, which is (in linear theory) the ratio of their bias factor b. We show that the ratio of the projected cross- and autocorrelation functions [W (r )/w (r )] is also the ratio of their bias factor, irrespective of the galaxy distribution, provided that one uses the same galaxies for w (r ) and w (r …

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J-Resolved He I Emission Predictions In The Low-Density Limit, R. P. Bauman, R. L. Porter, Gary J. Ferland, K. B. Macadam Jul 2005

J-Resolved He I Emission Predictions In The Low-Density Limit, R. P. Bauman, R. L. Porter, Gary J. Ferland, K. B. Macadam

Physics and Astronomy Faculty Publications

Determinations of the primordial helium abundance are used in precision cosmological tests. These require highly accurate He I recombination rate coefficients. Here we reconsider the formation of He I recombination lines in the low-density limit. This is the simplest case, and it forms the basis for the more complex situation in which collisions are important. The formation of a recombination line is a two-step process, beginning with the capture of a continuum electron into a bound state and followed by radiative cascade to ground. The rate coefficient for capture from the continuum is obtained from photoionization cross sections and detailed …

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Cosmic Rays From Gamma-Ray Bursts In The Galaxy, Charles Dennison Dermer, Jeremy M. Holmes Jul 2005

Cosmic Rays From Gamma-Ray Bursts In The Galaxy, Charles Dennison Dermer, Jeremy M. Holmes

Aerospace, Physics, and Space Science Faculty Publications

The rate of terrestrial irradiation events by Galactic gamma-ray bursts (GRBs) is estimated using recent standard-energy results. We assume that GRBs accelerate high-energy cosmic rays, and we present results of three-dimensional simulations of cosmic rays moving in the Galactic magnetic field and diffusing through pitch-angle scattering. An on-axis GRB extinction event begins with a powerful prompt γ-ray and neutron pulse, followed by a longer lived phase from cosmic-ray protons and neutron-decay protons that diffuse toward Earth. Our results force a reinterpretation of reported ∼10¹⁸ eV cosmic-ray anisotropies and offer a rigorous test of the model in which high-energy cosmic rays …

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Pulsar Timing And The Detection Of Black Hole Binary Systems In Globular Clusters, Fredrick A. Jenet, Teviet Creighton, Andrea Lommen Jul 2005

Pulsar Timing And The Detection Of Black Hole Binary Systems In Globular Clusters, Fredrick A. Jenet, Teviet Creighton, Andrea Lommen

Physics & Astronomy Faculty Publications

The possible existence of intermediate-mass binary black holes (IMBBHs) in globular clusters (GCs) offers us a unique geometry in which to detect spacetime oscillations. For certain pulsar-IMBBH configurations possible within a GC, the usual far-field plane wave approximation for the IMBBH metric perturbation severely underestimates the induced pulse time-of-arrival (TOA) fluctuations. In this Letter, the expected TOA fluctuations induced by an IMBBH lying close to the line of sight between a pulsar and the Earth are calculated for the first time. For an IMBBH consisting of 10 and 103 M⊙ components, a 10 yr orbital period, and located 0.1 lt-yr …

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Representations For Understanding The Stern-Gerlach Effect, Jared R. Stenson Jul 2005

Representations For Understanding The Stern-Gerlach Effect, Jared R. Stenson

Theses and Dissertations

The traditional explanation of the Stern-Gerlach effect carries with it several very subtle assumptions and approximations. We point out the degree to which this fact has affected the way we practice and interpret modern physics. In order to gain a more complete understanding of the Stern-Gerlach effect beyond the standard approximations and assumptions it typically carries, we introduce the inhomogeneous Stern-Gerlach effect in which the strong uniform field component is removed. This change allows us to easily identify precession as a critical concept. It also provides us with a means by which to study precession and analyze it critically. By …

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An Improved Flexible Neutron Detector For Powder Diffraction Experiments, Thomas Kevin Mcknight Jul 2005

An Improved Flexible Neutron Detector For Powder Diffraction Experiments, Thomas Kevin Mcknight

Theses and Dissertations

Large amounts of money are being applied to the construction of the next generation of spallation sources for neutron scattering. Neutron powder diffraction instruments will be an important element of these facilities and the incorporation of detectors into these instruments with a high neutron capture efficiency is desirable. A new detector design named the Flexible Embedded Fiber Detector (FEFD) has been developed and tested for this thesis. This detector is based on wavelength shifting fibers embedded in a zinc-sulfide lithium-fluoride based scintillator. The virtue of this design is that the detecting surface can be curved around the Debye-Scherrer rings. This …

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Black Spaghetti: A Numerical Model Of Gravitational Collapse In 4 + 1 Spacetime, Michael P. Christenson Jul 2005

Black Spaghetti: A Numerical Model Of Gravitational Collapse In 4 + 1 Spacetime, Michael P. Christenson

Theses and Dissertations

We investigate spherically-symmetric gravitational collapse in the presence of a single "large" extra dimension through the use of analytical and numerical techniques. This has bearing on higher-dimensional ideas concerning hypothetical objects called "black strings," or black holes extending into an extra circular dimension, which dimension we hereinafter label zeta. These putative objects were first seriously considered as elements of string theory but have relevance in simpler, higher-dimensional generalization of Einstein's general relativity. We assume a universe topologically consisting of a two-dimensional Lorentzian manifold crossed with the sphere, crossed again with the circle. We model the formation of a uniform black …

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Novel Neutron Detector For N-N Scattering Length Measurement, Eva Wilcox Jul 2005

Novel Neutron Detector For N-N Scattering Length Measurement, Eva Wilcox

Theses and Dissertations

The neutron-neutron (n-n) scattering length is a fundamental parameter in nuclear physics; however, measurements are plagued with large uncertainties caused by neutron detector cross talk. Many experimentalists also rely upon computer code to calibrate their neutron detectors. Experiments give one of two different numbers but there is still no adequate explanation for this discrepancy. We have developed a new neutron detector expressly for the purpose of improving the n-n scattering length measurement. It offers two important advantages: 1) minimal cross talk and 2) high counting efficiency. We calibrated the detector from 1 MeV to 6 MeV at 1 MeV increments. …

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Phase-Matching Optimization Of Laser High-Order Harmonics Generated In A Gas Cell, Julia Robin Miller Sutherland Jul 2005

Phase-Matching Optimization Of Laser High-Order Harmonics Generated In A Gas Cell, Julia Robin Miller Sutherland

Theses and Dissertations

Ten-millijoule, thirty-five femtosecond, 800 nm (~40 nm bandwidth) laser pulses are used to study high-order harmonic generation in helium- and neon-filled gas cells of various lengths. Harmonic orders in the range of 50 to 100 are investigated. A semi-infinite cell geometry produces brighter harmonics than cells of sub-centimeter length. In the semi-infinite geometry, the gas occupies the region from the focusing lens to a thin exit foil near the laser focus. Counter-propagating light is used to directly probe where the high harmonics are generated within the laser focus and to investigate phase matching. The phase matching under optimized harmonic generation …

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The Webt Campaign To Observe Ao 0235+16 In The 2003-2004 Observing Season - Results From Radio-To-Optical Monitoring And Xmm-Newton Observations, Niall Smith, Et. Al. Jul 2005

The Webt Campaign To Observe Ao 0235+16 In The 2003-2004 Observing Season - Results From Radio-To-Optical Monitoring And Xmm-Newton Observations, Niall Smith, Et. Al.

Blackrock Castle Observatory Publications

A multiwavelength campaign to observe the BL Lac object AO 0235+16 () was set up by the Whole Earth Blazar Telescope (WEBT) collaboration during the observing seasons 2003–2004 and 2004–2005, involving radio, near-IR and optical photometric monitoring, VLBA monitoring, optical spectral monitoring, and three pointings by the XMM-Newton satellite. Here we report on the results of the first season, which involved the participation of 24 optical and near-IR telescopes and 4 radio telescopes, as well as the first XMM-Newton pointing, which occurred on January 18–19, 2004. Unpublished data from previous epochs were also collected (from 5 optical-NIR and 3 radio …

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Optical Photometry And Spectroscopy Of The Suspected "Cool Algol" Av Delphini: Determination Of The Physical Properties, Jeff A. Mader, Laurence A. Marschall, Guillermo Torres, Akbar H. Rizvi Jul 2005

Optical Photometry And Spectroscopy Of The Suspected "Cool Algol" Av Delphini: Determination Of The Physical Properties, Jeff A. Mader, Laurence A. Marschall, Guillermo Torres, Akbar H. Rizvi

Physics and Astronomy Faculty Publications

We present new spectroscopic and BVRI photometric observations of the double-lined eclipsing binary AV Del ( period = 3:85 days) conducted over six observing seasons. A detailed radial velocity and light-curve analysis of the optical data shows the system to be most likely semidetached, with the less massive and cooler star filling its Roche lobe. The system is probably a member of the rare class of ‘‘cool Algol’’ systems, which are distinguished from the ‘‘classical’’ Algol systems in that the mass-gaining component is also a late-type star rather than a B- or A-type star. By combining the spectroscopic and photometric …

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The Model Dependence Of Solar Energetic Particle Mean Free Paths Under Weak Scattering, Gang Qin, Joseph R. Dwyer, Hamid K. Rassoul, Glenn M. Mason Jul 2005

The Model Dependence Of Solar Energetic Particle Mean Free Paths Under Weak Scattering, Gang Qin, Joseph R. Dwyer, Hamid K. Rassoul, Glenn M. Mason

Aerospace, Physics, and Space Science Faculty Publications

The mean free path is widely used to measure the level of solar energetic particles' diffusive transport. We model a solar energetic particle event observed by Wind STEP at 0.31-0.62 MeV nucleonˉ¹, by solving the focused transport equation using the Markov stochastic process theory. With different functions of the pitch angle diffusion coefficient D μμ, we obtain different parallel mean free paths for the same event. We show that the different values of the mean free path are due to the high anisotropy of the solar energetic particles. This makes it problematic to use just the mean free path to …

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A Multi-Instrument Study Of The Helix Nebula Knots With The Hubble Space Telescope, C. R. O'Dell, W. J. Henney, Gary J. Ferland Jul 2005

A Multi-Instrument Study Of The Helix Nebula Knots With The Hubble Space Telescope, C. R. O'Dell, W. J. Henney, Gary J. Ferland

Physics and Astronomy Faculty Publications

We have conducted a combined observational and theoretical investigation of the ubiquitous knots in the Helix Nebula (NGC 7293). We have constructed a combined hydrodynamic + radiation model for the ionized portion of these knots and have accurately calculated a static model for their molecular regions. Imaging observations in optical emission lines were made with the Hubble Space Telescope's STIS, operating in a "slitless" mode, complemented by WFPC2 images in several of the same lines. The NICMOS camera was used to image the knots in H2. These observations, when combined with other studies of H2 and …

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Dynamo Regimes With A Nonhelical Forcing, Pablo D. Mininni, Yannick Ponty, David C. Montgomery, Jean-Francois Pinton Jun 2005

Dynamo Regimes With A Nonhelical Forcing, Pablo D. Mininni, Yannick Ponty, David C. Montgomery, Jean-Francois Pinton

Dartmouth Scholarship

A three-dimensional numerical computation of magnetohydrodynamic dynamo behavior is described. The dynamo is mechanically forced with a driving term of the Taylor-Green type. The magnetic field development is followed from negligibly small levels to saturated values that occur at magnetic energies comparable to the kinetic energies. Although there is locally a nonzero helicity density, there is no overall integrated helicity in the system. Persistent oscillations are observed in the saturated state for not-too-large mechanical Reynolds numbers, oscillations in which the kinetic and magnetic energies vary out of phase but with no reversal of the magnetic field. The flow pattern exhibits …

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Late‐Time X‐Ray, Uv, And Optical Monitoring Of Supernova 1979c, Stefan Immler, Robert A. Fesen, Schuyler D. Van Dyk, Kurt W. Weiler, Robert Petre, Walter H.G Lewin, David Pooley, Wolfgang Pietsch, Bernd Aschenbach, Molly C. Hammell, Gwen C. Rudie Jun 2005

Late‐Time X‐Ray, Uv, And Optical Monitoring Of Supernova 1979c, Stefan Immler, Robert A. Fesen, Schuyler D. Van Dyk, Kurt W. Weiler, Robert Petre, Walter H.G Lewin, David Pooley, Wolfgang Pietsch, Bernd Aschenbach, Molly C. Hammell, Gwen C. Rudie

Dartmouth Scholarship

We present results from observations of supernova (SN) 1979C with the Newton X-Ray Multi-Mirror (XMM-Newton) mission in X-rays and in UV, archival X-ray, and Hubble Space Telescope (HST) data, and follow-up ground-based optical imaging. The XMM-Newton MOS spectrum shows the best-fit two-temperature thermal plasma emission characteristics of both the forward (kThigh = 4.1 keV) and reverse shock (kTlow = 0.79 keV) with no intrinsic absorption. The long-term X-ray light curve, constructed from all X-ray data available, reveals that SN 1979C is still radiating at a flux level similar to that detected by …

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Commutation Relations For Functions Of Operators, Mark K. Transtrum, Jean-Francois S. Van Huele Jun 2005

Commutation Relations For Functions Of Operators, Mark K. Transtrum, Jean-Francois S. Van Huele

Faculty Publications

We derive an expression for the commutator of functions of operators with constant commutations relations in terms of the partial derivatives of these functions. This result extends the well-known commutation relation between one operator and a function of another operator. We discuss the range of applicability of the formula with examples in quantum mechanics

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Eleven New Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry Jun 2005

Eleven New Γ Doradus Stars, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry

Information Systems and Engineering Management Research Publications

We present new high-dispersion spectroscopic and precise photometric observations to identify 11 new γ Doradus variables. Seven of these new γ Doradus stars appear to be single, three are primaries of single-lined binaries, and one has two distant visual companions; none are double-lined or close visual binaries. Several of the stars show spectroscopic line-profile and low-amplitude radial velocity variability indicative of pulsation. All 11 stars are photometrically variable with amplitudes between 8 and 93 mmag in Johnson B and periods between 0.398 and 2.454 days. One star is monoperiodic; the rest have between two and five independent periods. The variability …

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Co Line Emission And Absorption From The Hl Tauri Disk-Where Is All The Dust?, Sean D. Brittain, Terrence W. Rettig, Theodore Simon, Craig Kulesa Jun 2005

Co Line Emission And Absorption From The Hl Tauri Disk-Where Is All The Dust?, Sean D. Brittain, Terrence W. Rettig, Theodore Simon, Craig Kulesa

Publications

We present high-resolution infrared spectra of HL Tau, a heavily embedded young star. The spectra exhibit broad emission lines of 12CO gas-phase molecules, as well as narrow absorption lines of 12CO, 13CO, and C18O. The broad emission lines of vibrationally excited 12CO are dominated by the hot (T ~ 1500 K) inner disk. The narrow absorption lines of CO are found to originate from the circumstellar gas at a temperature of ~100 K. The 12CO column density for this cooler material [(7.5 ± 0.2) × 1018 cm-2] indicates a large column of absorbing gas along the line of sight. In …

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Evidence Of A Weak Galactic Center Magnetic Field From Diffuse Low-Frequency Nonthermal Radio Emission, Ted La Rosa, Crystal L. Brogan, Steven N. Shore, T. Joseph Lazio, Namir E. Kassim, Michael E. Nord Jun 2005

Evidence Of A Weak Galactic Center Magnetic Field From Diffuse Low-Frequency Nonthermal Radio Emission, Ted La Rosa, Crystal L. Brogan, Steven N. Shore, T. Joseph Lazio, Namir E. Kassim, Michael E. Nord

Faculty Articles

New low-frequency 74 and 330 MHz observations of the Galactic center (GC) region reveal the presence of a large-scale (6° × 2°) diffuse source of nonthermal synchrotron emission. A minimum-energy analysis of this emission yields a total energy of ~(phi4/7f3/7) × 1052 ergs and a magnetic field strength of ~6(phi/f)2/7 μG (where phi is the proton to electron energy ratio and f is the filling factor of the synchrotron emitting gas). The equipartition particle energy density is 1.2(phi/f)2/7 eV cm-3, a value consistent with cosmic-ray data. However, the derived magnetic field is several orders of magnitude below the 1 mG …

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Microgravity Studies Of Aggregation In Particulate Clouds, Todd B. Sauke, J. R. Marshall, J. N. Cuzzi Jun 2005

Microgravity Studies Of Aggregation In Particulate Clouds, Todd B. Sauke, J. R. Marshall, J. N. Cuzzi

Faculty Publications

Aggregation in clouds of submillimeter quartz and volcanic ash particles was studied in microgravity. Particle clouds generated by pulses of air immediately formed electrostatic filamentary aggregates upon cessation of air turbulence. Manual agitation of experiment chambers produced cm-size loose grain clusters which voraciously scavenged free-floating material in their vicinity. A dipole model accounts for these observations. Experimental results have ramifications for the behavior of natural cloud systems and primary accretion of solids in the early solar nebula.

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Detecting The Stochastic Gravitational Wave Background Using Pulsar Timing, Fredrick A. Jenet, George B. Hobbs, K. J. Lee, Richard N. Manchester Jun 2005

Detecting The Stochastic Gravitational Wave Background Using Pulsar Timing, Fredrick A. Jenet, George B. Hobbs, K. J. Lee, Richard N. Manchester

Physics & Astronomy Faculty Publications

The direct detection of gravitational waves is a major goal of current astrophysics. We provide details of a new method for detecting a stochastic background of gravitational waves using pulsar timing data. Our results show that regular timing observations of 40 pulsars each with a timing accuracy of 100 ns will be able to make a direct detection of the predicted stochastic background from coalescing black holes within 5 years. With an improved prewhitening algorithm, or if the background is at the upper end of the predicted range, a significant detection should be possible with only 20 pulsars. © 2005. …

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Erratum: Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer May 2005

Erratum: Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

Equation 14 in this paper contains errors.

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