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2003

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Articles 31 - 60 of 135

Full-Text Articles in Astrophysics and Astronomy

Phantom Energy: Dark Energy With W < − 1 Causes A Cosmic Doomsday, Robert R. Caldwell, Marc Kamionkowski, Nevin N. Weinberg Aug 2003

Phantom Energy: Dark Energy With W < − 1 Causes A Cosmic Doomsday, Robert R. Caldwell, Marc Kamionkowski, Nevin N. Weinberg

Dartmouth Scholarship

We explore the consequences that follow if the dark energy is phantom energy, in which the sum of the pressure and energy density is negative. The positive phantom-energy density becomes infinite in finite time, overcoming all other forms of matter, such that the gravitational repulsion rapidly brings our brief epoch of cosmic structure to a close. The phantom energy rips apart the Milky Way, solar system, Earth, and ultimately the molecules, atoms, nuclei, and nucleons of which we are composed, before the death of the Universe in a “big rip.”

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Mechanisms For The Origin Of Turbulence In Non-Star-Forming Clouds: The Translucent Cloud Mbm 40, Steven N. Shore, Loris Magnani, Ted La Rosa, Meredith N. Mccarthy Aug 2003

Mechanisms For The Origin Of Turbulence In Non-Star-Forming Clouds: The Translucent Cloud Mbm 40, Steven N. Shore, Loris Magnani, Ted La Rosa, Meredith N. Mccarthy

Faculty Articles

We present a multiline, high spatial and velocity resolution CO, H I, and IRAS 100 μm study of the high-latitude, low-mass, non-star-forming, translucent molecular cloud MBM 40. The cloud mass is distributed into two ridges, or filaments, that form a hairpin structure. Velocity channel maps indicate a highly ordered flow in the molecular gas, with the northeastern part of the filament moving away from and the southwestern filament moving toward the observer relative to the mean cloud radial velocity. Significant changes in emissivity occur over 0.03 pc, indicating large transverse density gradients along the ridges. However, the velocity field appears …

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A Search For Pure Disk Galaxies, Stefan Kautsch, Eva K. Grebel Aug 2003

A Search For Pure Disk Galaxies, Stefan Kautsch, Eva K. Grebel

Chemistry and Physics Faculty Proceedings, Presentations, Speeches, Lectures

Flat (or superthin) galaxies are late-type edge-on spiral galaxies that exhibit large axial ratios, small stellar disk scale heights and no distinct spheroidal bulge component. This type of galaxies appears to be a pure disk system with an extended blue stellar disk embedded in a red thick layer. Flat galaxies are very common objects with low star formation rates, low metallicities, low optical surface brightness but high neutral gas fractions. Their rotation curves resemble those of dwarf and irregular galaxies. These simple disk systems offer the unique opportunity to constrain galaxy disk evolution in underevolved galaxies in the nearby Universe. …

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X-Ray Emission-Line Profile Modeling Of O Stars: Fitting A Spherically Symmetric Analytic Wind-Shock Model To The Chandra Spectrum Of Zeta Puppis, Roban Hultman Kramer , '03, David H. Cohen, S. P. Owocki Jul 2003

X-Ray Emission-Line Profile Modeling Of O Stars: Fitting A Spherically Symmetric Analytic Wind-Shock Model To The Chandra Spectrum Of Zeta Puppis, Roban Hultman Kramer , '03, David H. Cohen, S. P. Owocki

Physics & Astronomy Faculty Works

X-ray emission-line profiles provide the most direct insight into the dynamics and spatial distribution of the hot, X-ray-emitting plasma above the surfaces of OB stars. The O supergiant zeta Puppis shows broad, blueshifted, and asymmetric line profiles, generally consistent with the wind-shock picture of OB star X-ray production. We model the profiles of eight lines in the Chandra HETGS spectrum of this prototypical hot star. The fitted lines indicate that the plasma is distributed throughout the wind starting close to the photosphere, that there is significantly less attenuation of the X-rays by the overlying wind than is generally supposed, and …

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Astrophysical Plasma Diagnostics Through Analysis Of Ar Iine Shape Characteristics, Vladimir Milosavljevic, Stevan Djenize Jul 2003

Astrophysical Plasma Diagnostics Through Analysis Of Ar Iine Shape Characteristics, Vladimir Milosavljevic, Stevan Djenize

Articles

On the basis of five accurately recorded neutral argon ( ) line shapes (in the 4s-5p transition) we have recovered the basic plasma parameters i.e. electron temperature ( T) and electron density ( N) using our new line deconvolution procedure in the case of three different plasmas created in a linear, low-pressure, pulsed arc discharge. The mentioned plasma parameters have also been measured using independent experimental diagnostic techniques. An excellent agreement has been found among the two sets of obtained parameters. This recommends our deconvolution procedure for plasma diagnostic purposes, especially in astrophysics where direct measurements of the …

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Early Quintessence In Light Of Thewilkinson Microwave Anisotropy Probe, Robert R. Caldwell, Michael Doran, Christian M. Mller, Gregor Schfer, Christof Wetterich Jul 2003

Early Quintessence In Light Of Thewilkinson Microwave Anisotropy Probe, Robert R. Caldwell, Michael Doran, Christian M. Mller, Gregor Schfer, Christof Wetterich

Dartmouth Scholarship

We examine the cosmic microwave background (CMB) anisotropy for signatures of early quintessence dark energy—a nonnegligible quintessence energy density during the recombination and structure formation eras. Only very recently does the quintessence overtake the dark matter and push the expansion into overdrive. Because the presence of early quintessence exerts an influence on the clustering of dark matter and the baryon-photon fluid, we may expect to find trace signals in the CMB and the mass fluctuation power spectrum. In detail, we demonstrate that suppressed clustering power on small length scales, as suggested by the combined Wilkinson Microwave Anisotropy Probe/CMB/large-scale structure …

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Multienergetic External-Beam Pixe As A Means Of Stydying The Surface Enrichment Effect In Coins, Scott Evans Perry Jul 2003

Multienergetic External-Beam Pixe As A Means Of Stydying The Surface Enrichment Effect In Coins, Scott Evans Perry

Theses and Dissertations

This thesis paper examines the feasibility of using external-beam PIXE to study the surface enrichment effect in metal artifacts. By varying the energy of the incident proton beam, we penetrated the artifact's surface to different levels and were able to produce a depth profile of the elemental composition of the sample. In this study, the sample set we chose to examine consisted of ancient and modern coins. This paper first describes the surface enrichment effect and theoretically how PIXE can be used to study it. It then details the construction of the components of the external-beam setup. Many of the …

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Rotational Velocities Of B, A, And Early‐F Narrow‐Lined Stars, Francis C. Fekel Jul 2003

Rotational Velocities Of B, A, And Early‐F Narrow‐Lined Stars, Francis C. Fekel

Information Systems and Engineering Management Research Publications

Projected rotational velocities for 58 B, A, and early‐F stars have been determined from high‐resolution spectroscopic observations made at Kitt Peak National Observatory with the coudé feed telescope. All the stars are slowly rotating with vsin i<60 km s−1. Because of their low rotational velocities, 15 of the stars have been observed as prospective, early‐type, radial velocity standards.

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Pks 0736+017: A Striking Optical Flare And Intriguing Microvariability, Sandra D. Clements, A Jenks, Y Torres Jul 2003

Pks 0736+017: A Striking Optical Flare And Intriguing Microvariability, Sandra D. Clements, A Jenks, Y Torres

Aerospace, Physics, and Space Science Faculty Publications

The compact, flat-spectrum radio quasar PKS 0736+017 was monitored for microvariability on 10 nights in early 2002 using the 0.9 m SARA telescope on Kitt Peak in Arizona. On January 14, PKS 0736+017 flared dramatically, brightening by 1.3 R mag in 2 hours. Prior to the flare, PKS 0736+017 exhibited quasi-periodic variations. During and after the flare, more complex oscillations occurred. Impressive variability was displayed on two additional nights in January, while observations during the following 3 months found PKS 0736+017 to be fairly quiescent. PKS 0736+017 was somewhat redder while brighter and fading than when dimmer but flaring. During …

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Observation Of And Model For Nonlinear Mode Conversion In A Non-Neutral Plasma, Grant W. Hart, Bryan G. Peterson, Ross L. Spencer Jul 2003

Observation Of And Model For Nonlinear Mode Conversion In A Non-Neutral Plasma, Grant W. Hart, Bryan G. Peterson, Ross L. Spencer

Faculty Publications

The nonlinear interaction of the two lowest Trivelpiece-Gould modes in a non-neutral plasma has been observed. Because of coupling in the nonlinear terms of the continuity and momentum equations, the two modes can exchange energy and convert one to the other. This can be modeled using the cold fluid equations and the averaging method. Experimentally, this process always stops with the lower frequency mode dominating the final state. Numerical integration of the model suggests that this occurs because the higher frequency mode is more strongly damped than the lower frequency mode.

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Multisite Observations Of The Pms Δ Delta Scuti Star V351 Ori, V. Ripepi, Terry D. Oswalt, M. Marconi, S. Bernabei, Et Al. Jun 2003

Multisite Observations Of The Pms Δ Delta Scuti Star V351 Ori, V. Ripepi, Terry D. Oswalt, M. Marconi, S. Bernabei, Et Al.

Publications

We present the results of multisite observations spanning two years on the pre–main-sequence (PMS) star V351 Ori. A total of around 180 hours of observations over 29 nights have been collected, allowing us to measure five different periodicities, most likely related to the Scuti variability of V351 Ori. Comparison with the predictions of linear nonadiabatic radial pulsation models put stringent constraints on the stellar parameters and indicate that the distance to V351 Ori is intermediate between the lower limit measured by Hipparcos (210 pc) and that of the Orion Nebula (450 pc). However, radial pulsation models are unable to reproduce …

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Iteration Methods For Approximating The Lowest Order Energy Eigenstate Of A Given Symmetry For One- And Two-Dimensional Systems, Chad Everett Junkermeier Jun 2003

Iteration Methods For Approximating The Lowest Order Energy Eigenstate Of A Given Symmetry For One- And Two-Dimensional Systems, Chad Everett Junkermeier

Theses and Dissertations

Using the idea that a quantum mechanical system drops to its ground state as its temperature goes to absolute zero several operators are devised to enable the approximation of the lowest order energy eigenstate of a given symmetry; as well as an approximation to the energy eigenvalue of the same order.

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The Flaring H2o Megamaser And Compact Radio Source In Markarian 348, A. B. Peck, C. Henkel, J. S. Ulvestad, A. Brunthaler, H. Falcke, Moshe Elitzur, K. M. Menten, J. F. Gallimore Jun 2003

The Flaring H2o Megamaser And Compact Radio Source In Markarian 348, A. B. Peck, C. Henkel, J. S. Ulvestad, A. Brunthaler, H. Falcke, Moshe Elitzur, K. M. Menten, J. F. Gallimore

Physics and Astronomy Faculty Publications

We report on single-dish monitoring and extremely high angular resolution observations of the flaring H2O megamaser in the Seyfert 2 galaxy Mrk 348. The H2O line is redshifted by ~130 km s-1 with respect to the systemic velocity, is very broad, with an FWHM of 130 km s-1, and has no detectable high-velocity components within 1500 km s-1 on either side of the strong line. Monitoring observations made with the Effelsberg 100 m telescope show that the maser varies significantly on timescales as short as 1 day and that the integrated line …

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Nonlinear Collisionless Perpendicular Diffusion Of Charged Particles, William H. Matthaeus, Gang Qin, John William Bieber, Gary Paul Zank Jun 2003

Nonlinear Collisionless Perpendicular Diffusion Of Charged Particles, William H. Matthaeus, Gang Qin, John William Bieber, Gary Paul Zank

Aerospace, Physics, and Space Science Faculty Publications

A nonlinear theory of the perpendicular diffusion of charged particles is presented, including the influence of parallel scattering and dynamical turbulence. The theory shows encouraging agreement with numerical simulations.

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Grb 021004: A Possible Shell Nebula Around A Wolf‐Rayet Star Gamma‐Ray Burst Progenitor, N. Mirabal, J. P. Halpern, Ryan Chornock, Alexei V. Filippenko, D. M. Terndrup, E. Armstrong, J. Kemp, J. R. Thorstensen, M. Tavarez, C. Espaillat Jun 2003

Grb 021004: A Possible Shell Nebula Around A Wolf‐Rayet Star Gamma‐Ray Burst Progenitor, N. Mirabal, J. P. Halpern, Ryan Chornock, Alexei V. Filippenko, D. M. Terndrup, E. Armstrong, J. Kemp, J. R. Thorstensen, M. Tavarez, C. Espaillat

Dartmouth Scholarship

The rapid localization of GRB 021004 by the HETE-2 satellite allowed nearly continuous monitoring of its early optical afterglow decay, as well as high-quality optical spectra that determined a redshift of z3 = 2.328 for its host galaxy, an active starburst galaxy with strong Ly emission and several absorption lines. Spectral observations show multiple absorbers at z3A = 2.323, z3B= 2.317, and z3C = 2.293 blueshifted by ~450, ~990, and ~3155 km s-1, respectively, relative to the host galaxy Lyα emission. We argue that these correspond to a fragmented shell nebula that has …

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Optical Photometry And X-Ray Monitoring Of The "Cool Algol" Bd+05˚706: Determination Of The Physical Properties, Guillermo Torres, Jeff A. Mader, Laurence A. Marschall, Ralph Neuhauser, Alaine S. Duffy Jun 2003

Optical Photometry And X-Ray Monitoring Of The "Cool Algol" Bd+05˚706: Determination Of The Physical Properties, Guillermo Torres, Jeff A. Mader, Laurence A. Marschall, Ralph Neuhauser, Alaine S. Duffy

Physics and Astronomy Faculty Publications

We present new photometric observations in the BVRI bands of the double-lined eclipsing binary BD +05706 conducted over three observing seasons, as well as new X-ray observations obtained with ROSAT covering a full orbital cycle (P = 18.9 days). A detailed light-curve analysis of the optical data shows the system to be semidetached, confirming indications from an earlier analysis by Torres et al. (published in 1998), with the less massive and cooler star filling its Roche lobe. The system is a member of the rare class of cool Algol systems, which are different from the ‘‘ classical ’’ Algol systems …

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Morphological Biosignatures And The Search For Life On Mars, Sherry L. Cady, Jack D. Farmer, John P. Grotzinger, J. William Schopf, Andrew Steele Jun 2003

Morphological Biosignatures And The Search For Life On Mars, Sherry L. Cady, Jack D. Farmer, John P. Grotzinger, J. William Schopf, Andrew Steele

Geology Faculty Publications and Presentations

This report provides a rationale for the advances in instrumentation and understanding needed to assess claims of ancient and extraterrestrial life made on the basis of morphological biosignatures. Morphological biosignatures consist of bona fide microbial fossils as well as microbially influenced sedimentary structures. To be recognized as evidence of life, microbial fossils must contain chemical and structural attributes uniquely indicative of microbial cells or cellular or extracellular processes. When combined with various research strategies, high-resolution instruments can reveal such attributes and elucidate how morphological fossils form and become altered, thereby improving the ability to recognize them in the geological record …

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Black Hole Attractor Varieties And Complex Multiplication, Monika Lynker, Vipul Periwal, Rolf Schimmrigk Jun 2003

Black Hole Attractor Varieties And Complex Multiplication, Monika Lynker, Vipul Periwal, Rolf Schimmrigk

Faculty Articles

Black holes in string theory compactified on Calabi-Yau varieties a priori might be expected to have moduli dependent features. For example the entropy of the black hole might be expected to depend on the complex structure of the manifold. This would be inconsistent with known properties of black holes. Supersymmetric black holes appear to evade this inconsistency by having moduli fields that flow to fixed points in the moduli space that depend only on the charges of the black hole. Moore observed in the case of compactifications with elliptic curve factors that these fixed points are arithmetic, corresponding to curves …

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Spatially Resolved Spectroscopy Of Coma Cluster Early-Type Galaxies - Iii. The Stellar Population Gradients, D. Mehlert, D. Thomas, R. P. Saglia, R. Bender, G Wegner May 2003

Spatially Resolved Spectroscopy Of Coma Cluster Early-Type Galaxies - Iii. The Stellar Population Gradients, D. Mehlert, D. Thomas, R. P. Saglia, R. Bender, G Wegner

Dartmouth Scholarship

Based on Paper I of this series (Mehlert et al. 2000), we derive central values and logarithmic gradients for the Hβ, Mg and Fe indices of 35 early-type galaxies in the Coma cluster. We find that pure elliptical galaxies have on average slightly higher velocity dispersions, lower Hβ, and higher metallic line-strengths than galaxies with disks (S0). The latter form two families, one comparable to the ellipticals and a second one with significantly higher Hβ, and weaker metallic lines. Our measured logarithmic gradients within the effective radius are ⟨△Mg b⟩ ≈ −0.037, ⟨△⟨Fe⟩⟩ ≈ −0.029, ⟨△Hβ⟩ ≈ +0.017 and ⟨△σ⟩ …

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Effects Of The Sound Speed Of Quintessence On The Microwave Background And Large Scale Structure, Simon Dedeo, R. R. Caldwell, Paul J. Steinhardt May 2003

Effects Of The Sound Speed Of Quintessence On The Microwave Background And Large Scale Structure, Simon Dedeo, R. R. Caldwell, Paul J. Steinhardt

Dartmouth Scholarship

We consider how quintessence models in which the sound speed differs from the speed of light and varies with time affect the cosmic microwave background and the fluctuation power spectrum. Significant modifications occur on length scales related to the Hubble radius during epochs in which the sound speed is near zero and the quintessence contributes a non-negligible fraction of the total energy density. For the microwave background, we find that the usual enhancement of the lowest multipole moments by the integrated Sachs-Wolfe effect can be modified, resulting in suppression or bumps instead. Also, the sound speed can produce oscillations and …

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Evidence For A Suprathermal Seed Population Of Heavy Ions Accelerated By Interplanetary Shocks Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Charles W. Smith, Ruth M. Skoug May 2003

Evidence For A Suprathermal Seed Population Of Heavy Ions Accelerated By Interplanetary Shocks Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Charles W. Smith, Ruth M. Skoug

Aerospace, Physics, and Space Science Faculty Publications

We have surveyed the 0.1-10 MeV nucleonˉ¹ elemental abundances at 72 interplanetary (IP) shocks observed by the Ultra-Low-Energy Isotope Spectrometer on board the Advanced Composition Explorer from 1997 October through 2002 September. We find the following: (1) The C/O ratios in IP shocks were substantially depleted (by more than ∼40%) relative to solar wind values. (2) The IP shock abundances were poorly correlated with those measured in the slow and fast solar wind. (3) Energetic ions above ∼0.1 MeV nucleonˉ¹ from impulsive and gradual solar energetic particle events (SEPs) were present upstream of all the IP shocks in our survey. …

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Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson May 2003

Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson

Pomona Senior Theses

This report details work toward the fabrication of a single-electron transistor created from a single-walled carbon nanotube (SWNT). Specifically discussed is a method for growing carbon nanotubes (CNTs) via carbon vapor deposition (CVD). The growth is catalyzed by a solution of 0.02g Fe(NO3)3·9H2O, 0.005g MoO2(acac)2, and 0.015g of alumina particles in 15mL methanol. SWNT diameter ranges from 0.6 to 3.0 nm. Also discussed is a method to control nanotube growth location by patterning samples with small islands of catalyst. A novel “maskless” photolithographic process is used to focus light from a lightweight commercial digital projector through a microscope. Catalyst islands …

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Maskless Projection Lithography, J. David Musgraves May 2003

Maskless Projection Lithography, J. David Musgraves

Pomona Senior Theses

Photolithography is a key element of the modem integrated circuit process. It is photolithography, combined with metal deposition, that allows a three dimensional circuit to be built up on a two dimensional surface. Since it is such an important part of the semiconductor manufacturing industry, a massive base of research in this area already exists. The problem with this pre-existing research is that it is geared solely toward industrial purposes, as opposed to more academic research areas. The goal of my research is to move this industrial process into the academic setting of Pomom College.

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Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson May 2003

Steps Toward The Creation Of A Carbon Nanotube Single Electron Transistor, R. Matthew Ferguson

Pomona Senior Theses

This report details work toward the fabrication of a single-electron transistor created from a single-walled carbon nanotube (SWNT). Specifically discussed is a method for growing carbon nanotubes (CNTs) via carbon vapor deposition (CVD). The growth is catalyzed by a solution of 0.02g Fe(NO3)3·9H2O, 0.005g MoO2(acac)2, and 0.015g of alumina particles in 15mL methanol. SWNT diameter ranges from 0.6 to 3.0 nm. Also discussed is a method to control nanotube growth location by patterning samples with small islands of catalyst. A novel “maskless” photolithographic process is used to focus light from a lightweight commercial digital projector through a microscope. Catalyst islands …

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Redshift-Distance Survey Of Early-Type Galaxies: Circular-Aperture Photometry, M. V. Alonso, M. Bernardi, L. N. Da Costa, G. Wegner May 2003

Redshift-Distance Survey Of Early-Type Galaxies: Circular-Aperture Photometry, M. V. Alonso, M. Bernardi, L. N. Da Costa, G. Wegner

Dartmouth Scholarship

We present R -band CCD photometry for 1332 early-type galaxies, observed as part of the ENEAR survey of peculiar motions using early-type galaxies in the nearby universe. Circular apertures are used to trace the surface brightness profiles, which are then fitted by a two-component bulge-disk model. From the fits, we obtain the structural parameters required to estimate galaxy distances using the Dn - and fundamental plane relations. We find that about 12% of the galaxies are well represented by a pure r1/4 law, while 87% are best fitted by a two-component model. There are 356 repeated observations of 257 galaxies …

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Spectroscopy Of Kiss Emission-Line Galaxy Candidates. I. Mdm Observations, Gary Wegner, John J. Salzer, Anna Jangren, Caryl Gronwall, Jason Melbourne May 2003

Spectroscopy Of Kiss Emission-Line Galaxy Candidates. I. Mdm Observations, Gary Wegner, John J. Salzer, Anna Jangren, Caryl Gronwall, Jason Melbourne

Dartmouth Scholarship

Spectroscopic observations for 351 emission-line galaxy candidates from the KPNO International Spectroscopic Survey (KISS) have been obtained using the MDM Observatory 2.4 m telescope on Kitt Peak. KISS is an ongoing wide-field objective-prism survey for extragalactic emission-line objects, which has cataloged over 2200 emission-line galaxy (ELG) candidates to date. Spectroscopic follow-up observations are being carried out to study the characteristics of the survey objects. The observational data presented here include redshifts, reddening estimates, line equivalent widths, Hα line fluxes, and emission-line ratios. The galaxies have been classified based on their emission-line characteristics. The procedure for selecting the ELG candidates in …

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Decay Of Trapped-Particle Asymmetry Modes In Non-Neutral Plasmas In A Malmberg-Penning Trap, Grant W. Mason May 2003

Decay Of Trapped-Particle Asymmetry Modes In Non-Neutral Plasmas In A Malmberg-Penning Trap, Grant W. Mason

Faculty Publications

The mechanism for the strong damping of diocotron-like azimuthal trapped-particle asymmetry modes in a Malmberg-Penning trap is investigated with a detailed three-dimensional particle-in-cell computer simulation. The m = 1,kzis not equal to 0 modes are created by a voltage squeeze from a mid-detector ring followed by a displacement of trapped particles in opposite directions on either side of the ring. The voltage squeeze creates a population of particles confined to half the trap length (trapped) and a population of particles that move longitudinally along the full length of the cylinder (untrapped). The damping of the modes is found to be …

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Optically Oriented And Detected Electron Spin Resonance In A Lightly Doped N-Gaas Layer, John S. Colton, T. A. Kennedy, A. S. Bracker, D. Gammon, J. B. Miller Apr 2003

Optically Oriented And Detected Electron Spin Resonance In A Lightly Doped N-Gaas Layer, John S. Colton, T. A. Kennedy, A. S. Bracker, D. Gammon, J. B. Miller

Faculty Publications

Spin resonance of localized electrons bound to donors in a specially designed n-GaAs layer has been performed at 236 MHz and 41 mT, using circular polarized light to polarize the electrons and photoluminescence to detect the electronic polarization. The polarization was diminished under the resonance condition. The electronic g factor obtained by this measurement is - 0.41 ± 0.01. The resonance linewidth of 2 mT corresponds to a spin lifetime of 28 ns. In order to observe the electronic spin resonance, nuclear effects were eliminated by application of rf fields to simultaneously resonate the nuclear spins.

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Bv Photometry Of Ux Ari In The Period 1987–2002, Vidar Aarum Ulvås, Gregory W. Henry Apr 2003

Bv Photometry Of Ux Ari In The Period 1987–2002, Vidar Aarum Ulvås, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We present 14.3 years of previously unpublished photometric observations of UX Ari. The observations were obtained between 1987.9 and 2002.2 using the T3 0.4-metre Automatic Photoelectric Telescope at Fairborn Observatory and consist of 1228 B band and 1213 V band measurements. The comparison star was 62 Ari. We have analyzed the new data together with previously published photometric observations. The V magnitude shows variations with dominant periods of about 12 and 25 years, where the longest period seems to correspond to an activity cycle. The previously reported anticorrelation between the colour and V magnitude variations is confirmed.

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An Extended Burst Tail From Sgr 1900+14 With A Thermal X-Ray Spectrum, Geoffrey T. Lenters, Peter M. Woods, Johnathan E. Goupell, Chryssa Kouveliotou Apr 2003

An Extended Burst Tail From Sgr 1900+14 With A Thermal X-Ray Spectrum, Geoffrey T. Lenters, Peter M. Woods, Johnathan E. Goupell, Chryssa Kouveliotou

University Faculty Publications and Creative Works

The soft gamma repeater SGR 1900+14 entered a new phase of activity in 2001 April initiated by the intermediate flare recorded on April 18. Ten days following this flare, we discovered an abrupt increase in the source flux between consecutive Rossi X-Ray Timing Explorer (RXTE) orbits. This X-ray flux excess decayed over the next several minutes and was subsequently linked to a high fluence burst from SGR 1900+14 recorded by other spacecraft (Ulysses and Wind/Konus) while the SGR was Earth-occulted for RXTE. We present here spectral and temporal analysis of both the burst of April 28 and the long X-ray …

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