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Astrophysics and Astronomy

2004

Series

Embry-Riddle Aeronautical University

Articles 1 - 19 of 19

Full-Text Articles in Physical Sciences and Mathematics

The Initial-Final Mass Relationship: Spectroscopy Of White Dwarfs In Ngc 2099 (M37), Jasonjot Singh Kalirai, Ted Von Hippel, Et Al. Dec 2004

The Initial-Final Mass Relationship: Spectroscopy Of White Dwarfs In Ngc 2099 (M37), Jasonjot Singh Kalirai, Ted Von Hippel, Et Al.

Publications

We present new observations of very faint white dwarfs (WDs) in the rich open star cluster NGC 2099 (M37). Following deep, wide-field imaging of the cluster using the Canada-France-Hawaii Telescope, we have now obtained spectroscopic observations of candidate WDs using both the Gemini Multi-Object Spectrograph on Gemini North and the Low-Resolution Imaging Spectrometer on Keck. Of our 24 WD candidates (all fainter than V = 22.4), 21 are spectroscopically confirmed to be bona fide WDs, four or five of which are most likely field objects. Fitting 18 of the 21 WD spectra with model atmospheres, we find that most WDs …

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Coordinate Conditions For A Uniformly Accelerated Or Static Plane Symmetric Metric, Preston Jones, Lucas Wanex Dec 2004

Coordinate Conditions For A Uniformly Accelerated Or Static Plane Symmetric Metric, Preston Jones, Lucas Wanex

Publications

The coordinate conditions for three exact solutions for the metric components of a coordinate system with constant acceleration or of a static plane symmetric gravitational field are presented. First, the coordinate condition that the acceleration of light is constant is applied to the field equations to derive the metric of a coordinate system of constant acceleration. Second, the coordinate conditions required to produce the metrics of Rindler and Lass are applied to the field equations to calculate the components of these two metrics and the coordinate velocities and coordinate accelerations for light of these two metrics are compared to the …

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Geocoronal Hydrogen Studies Using Fabry-Perot Interferometers, S. M. Nossal, E. J. Mierkiewicz, F. L. Roesler, J. Bishop, R. J. Reynolds Nov 2004

Geocoronal Hydrogen Studies Using Fabry-Perot Interferometers, S. M. Nossal, E. J. Mierkiewicz, F. L. Roesler, J. Bishop, R. J. Reynolds

Publications

Ground based Fabry-Perot observations of solar excited geocoronal hydrogen fluorescence emissions are one of the primary means of studying the neutral upper atmosphere [Atreya et al., 1975; Meriwether et al., 1980; Yelle and Roesler, 1985; Shih et al., 1985; Kerr et al., 2001a,b; He et al., 1993; Nossal et al., 1993, 1998, 2004; Bishop et al., 2001; Mierkiewicz, 2002; and references therein]. Excellent reviews of early ground-based geocoronal Balmer α observations are found in: Krassovsky et al. [1966], Krassovsky [1971], Donahue [1964, 1966], Tinsley [1974], Fahr and Shizgal [1983] and Kerr et al. [2001a]. Instruments onboard satellites and rockets also …

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The White Dwarf Luminosity Function: The Shape Of Things To Come, Ted Von Hippel, M. Kilie, J. Munn, K. Williams, J. Libert, D. E. Winget, T. S. Metcalfe, Et Al. Oct 2004

The White Dwarf Luminosity Function: The Shape Of Things To Come, Ted Von Hippel, M. Kilie, J. Munn, K. Williams, J. Libert, D. E. Winget, T. S. Metcalfe, Et Al.

Publications

We describe a new survey for cool white dwarfs that supplements Sloan Digital Sky Survey photometry with USNO proper motions and followup spectroscopy. To date we have discovered and spectroscopically confirmed 80 new moderate temperature and cool white dwarfs. We have also found a handful of high-velocity white dwarfs and we expect a sizable fraction of these to be thick disk or possibly halo objects. Our survey is designed to find 104 new white dwarfs, although only 60 will be among the faintest white dwarfs (MV 16), where most of the age-sensitivity resides. We discuss an extension of our survey …

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Photometric Identification Of Cool White Dwarfs, M. Kilic, D. E. Winget, Ted Von Hippel, C. F. Claver Oct 2004

Photometric Identification Of Cool White Dwarfs, M. Kilic, D. E. Winget, Ted Von Hippel, C. F. Claver

Publications

We investigate the use of a narrowband DDO51 filter for photometric identification of cool white dwarfs. We report photometric observations of 30 known cool white dwarfs with temperatures ranging from 10,000 K down to very cool temperatures (3500 K). Follow-up spectroscopic observations of a sample of objects selected using this filter and our photometric observations show that DDO51 filter photometry can help select cool white dwarf candidates for follow-up multiobject spectroscopy by rejecting 65% of main-sequence stars with the same broadband colors as the cool white dwarfs. This technique is not selective enough to efficiently feed single-object spectrographs. We present …

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Redefining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, Et Al. Sep 2004

Redefining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, Et Al.

Publications

We use the new ZZ Ceti stars (hydrogen-atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to redefine the empirical ZZ Ceti instability strip. This is the first time since the discovery of white dwarf variables in 1968 that we have a homogeneous set of spectra acquired using the same instrument on the same telescope, and with consistent data reductions, for a statistically significant sample of ZZ Ceti stars. The homogeneity of the spectra reduces the scatter in the spectroscopic temperatures, and we find a narrow instability strip of width ~950 K, from …

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Book Review: Sky Vistas: Astronomy For Binoculars And Richestfield Telescopes, T. D. Oswalt Sep 2004

Book Review: Sky Vistas: Astronomy For Binoculars And Richestfield Telescopes, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Sky Vistas : Astronomy for Binoculars and Richestfield Telescopes by Craig Crossen and Gerald Rhemann Springer, 2004 279p, 3211008519 $69.95

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Lorentz-Violating Electromagnetostatics, Quentin G. Bailey Aug 2004

Lorentz-Violating Electromagnetostatics, Quentin G. Bailey

Publications

In this talk, the stationary limit of Lorentz-violating electrodynamics is discussed. As illustrated by some simple examples, the general solution includes unconventional mixing of electrostatic and magnetostatic effects. I discuss a high-sensitivity null-type measurement, exploiting Lorentz-violating electromagnetostatic effects, that could improve existing limits on parity-odd coefficients for Lorentz violation in the photon sector.

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Proper Motion Objects In The Hubble Deep Field, M. Kilic, Ted Von Hippel, Et Al. Jul 2004

Proper Motion Objects In The Hubble Deep Field, M. Kilic, Ted Von Hippel, Et Al.

Publications

Using the deepest and finest resolution images of the universe acquired with the Hubble Space Telescope and a similar image taken 7 yr later for the Great Observatories Origins Deep Survey, we have derived proper motions for the point sources in the Hubble Deep Field–North. Two faint blue objects, HDF 2234 and HDF 3072, are found to display significant proper motion, 10:0 ± 2:5 and 15:5 ± 3:8 mas yr¯1. Photometric distances and tangential velocities for these stars are consistent with disk white dwarfs located at ~500 pc. The faint blue objects analyzed by Ibata et al. and Mendez & …

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Cluster Observations Of Magnetic Field Fluctuations In The High-Altitude Cusp, K. Nykyri, P. J. Cargill, E. Lucek, T. Horbury, B. Lavraud, A. Balogh, M. W. Dunlop, Et Al. Jul 2004

Cluster Observations Of Magnetic Field Fluctuations In The High-Altitude Cusp, K. Nykyri, P. J. Cargill, E. Lucek, T. Horbury, B. Lavraud, A. Balogh, M. W. Dunlop, Et Al.

Publications

High-resolution (22 vector/s) magnetic field data from Cluster FGM instrument are presented for the highaltitude cusp crossing on 17 March 2001. Despite the quiet solar wind conditions, the cusp was filled with magnetic field turbulence for much of the crossing. Large-scale fluctuations show some correlation between spacecraft but the higher frequency fluctuations show no correlation, indicating that the length scales of these waves are smaller than the spacecraft separation (500 km). In many intervals, there are clear peaks in the wave power around the ion cyclotron frequency (~1 Hz), and there is some evidence for waves at the first harmonic …

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Thirty-Five New Pulsating Da White Dwarf Stars, Anjum S. Mukadam, Ted Von Hippel, Et Al. Jun 2004

Thirty-Five New Pulsating Da White Dwarf Stars, Anjum S. Mukadam, Ted Von Hippel, Et Al.

Publications

We present 35 new pulsating DA (hydrogen atmosphere) white dwarf stars discovered from the Sloan Digital Sky Survey (SDSS) and the Hamburg Quasar Survey (HQS). We have acquired high-speed time series photometry of preselected DA white dwarfs with a prime focus CCD photometer on the 2.1 m telescope at McDonald Observatory over 15 months. We selected these stars on the basis of prior photometric and spectroscopic observations by the SDSS and HQS. For the homogeneous SDSS sample, we achieve a success rate of 80% for finding new variables at a detection threshold of 0.1%-0.3%. With 35 newly discovered DA variable …

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Book Review: The Edge Of Infinity: Supermassive Black Holes In The Universe, T. D. Oswalt Jun 2004

Book Review: The Edge Of Infinity: Supermassive Black Holes In The Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Edge of Infinity : Supermassive Black Holes in the Universe by Fulvio Melia. Cambridge, 2003 148p, 0-521-81405-7 $30.00.

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Re-Defining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, D. E. Winget,, M. H. Montgomery May 2004

Re-Defining The Empirical Zz Ceti Instability Strip, Anjum S. Mukadam, Ted Von Hippel, D. E. Winget,, M. H. Montgomery

Publications

We use the new ZZ Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to re-define the empirical ZZ Ceti instability strip. This is the first time since the discovery of white dwarf variables in 1968 that we have a homogeneous set of spectra acquired using the same instrument on the same telescope, and with con- sistent data reductions, for a statistically significant sample of ZZ Ceti stars. The homogeneity of the spectra reduces the scatter in the spectroscopic temperatures and we find a narrow instability strip of width ∼ …

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Data-Model Comparison Search Analysis Of Coincident Pbo Balmer Α, Eurd Lyman Β Geocoronal Measurements From March 2000, J. Bishop, E. J. Mierkiewicz, F. L. Roesler, J. F. Gómez, C. Morales May 2004

Data-Model Comparison Search Analysis Of Coincident Pbo Balmer Α, Eurd Lyman Β Geocoronal Measurements From March 2000, J. Bishop, E. J. Mierkiewicz, F. L. Roesler, J. F. Gómez, C. Morales

Publications

Recent Lyman series and Balmer series airglow measurements provide a fresh opportunity to investigate the density distribution and variability of atomic hydrogen in the upper atmosphere. Dedicated nightside Balmer α Fabry-Perot spectrometer measurements at the Pine Bluff Observatory (PBO), University of Wisconsin-Madison, have been acquired since late 1999 taking advantage of several technological advances. Extreme ultraviolet spectral radiance measurements by the Espectrógrafo Ultravioleta extremo para la Radiación Difusa (EURD) instrument on the Spanish MINISAT-1 satellite from October 1997 to December 2001 provide extensive sets of geocoronal Lyman β, Lyman γ and He 584 Å emission intensities. In this paper, coincident …

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Spectroscopic And Photometric Analysis Of Hs 1136+6646: A Hot Young Dao+K7 V Post-Common-Envelope, Pre-Cataclysmic Variable Binary, D. K. Sing, Terry D. Oswalt, J. B. Holberg, M. R. Burleigh, S. A. Good, Et Al. May 2004

Spectroscopic And Photometric Analysis Of Hs 1136+6646: A Hot Young Dao+K7 V Post-Common-Envelope, Pre-Cataclysmic Variable Binary, D. K. Sing, Terry D. Oswalt, J. B. Holberg, M. R. Burleigh, S. A. Good, Et Al.

Publications

Extensive photometric and spectroscopic observations have been obtained for HS 1136+6646. The observations reveal a newly formed post–common-envelope binary system containing a hot ~DAO.5 primary and a highly irradiated secondary. HS 1136+6646 is the most extreme example yet of a class of short-period hot H-rich white dwarfs with K–M companion systems such as V471 Tau and Feige 24. HS 1136+6646 is a double-line spectroscopic binary showing emission lines of H i, He ii, C ii, Ca ii, and Mg ii, due in part to irradiation of the K7 V secondary by the hot white dwarf. Echelle spectra reveal the hydrogen …

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Cluster Encounters With The High Altitude Cusp: Boundary Structure And Magnetic Field Depletions, P. J. Cargill, M. W. Dunlop, B. Lavraud, R. C. Elphic, D. L. Holland, K. Nykyri, A. Balogh, I. Dandouras Apr 2004

Cluster Encounters With The High Altitude Cusp: Boundary Structure And Magnetic Field Depletions, P. J. Cargill, M. W. Dunlop, B. Lavraud, R. C. Elphic, D. L. Holland, K. Nykyri, A. Balogh, I. Dandouras

Publications

Data from the four spacecraft Cluster mission during a high altitude cusp crossing on 13 February 2001 are presented. The spacecraft configuration has one leading spacecraft, with the three trailing spacecraft lying in a plane that corresponds roughly to the nominal magnetopause surface. The typical spacecraft separation is approximately 600 km. The encounter occurs under conditions of strong and steady southward Interplanetary Magnetic Field (IMF). The cusp is identified as a seven-minute long depression in the magnetic field, associated with ion heating and a high abundance of He+. Cusp entry involves passage through a magnetopause boundary that has undergone very …

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Observations Of Solar Cyclical Variations In Geocoronal Hα Column Emission Intensities, S. M. Nossal, F. L. Roesler, E. J. Mierkiewicz, R. J. Reynolds Mar 2004

Observations Of Solar Cyclical Variations In Geocoronal Hα Column Emission Intensities, S. M. Nossal, F. L. Roesler, E. J. Mierkiewicz, R. J. Reynolds

Physical Sciences - Daytona Beach

Observations of thermospheric + exospheric Hα column emissions by the Wisconsin Hα Mapper (WHAM) Fabry-Perot (Kitt Peak, Arizona) over the 1997–2001 rise in solar cycle 23 show a statistically significant solar cyclical variation. The higher signal-to-noise WHAM observations corroborate suggestions of a solar cycle trend in the Hα emissions seen in Wisconsin observations over solar cycle 22. Here we compare WHAM 1997 and 2000–2001 winter solstice geocoronal Hα observations toward regions of the sky with low galactic emission. The observed variation in geocoronal hydrogen column emission intensities over the solar cycle is small compared with variations in hydrogen exobase densities. …

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Book Review: The Big Bang: A View From The 21st Century, T. D. Oswalt Feb 2004

Book Review: The Big Bang: A View From The 21st Century, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Big Bang : a View from the 21st Century by David M. Harland. Springer/Praxis, 2003 262p, 1-85233-713-3 $39.95.

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Influence Of The Hall Term On Kh Instability And Reconnection Inside Kh Vortices, K. Nykyri, A. Otto Feb 2004

Influence Of The Hall Term On Kh Instability And Reconnection Inside Kh Vortices, K. Nykyri, A. Otto

Publications

The Kelvin-Helmholtz instability (KHI) in its nonlinear stage can develop small-scale filamentary field and current structures at the flank boundaries of the magnetosphere. It has been shown previously with MHD simulations that magnetic reconnection can occur inside these narrow current layers, resulting in plasma transport from the solar wind into the magnetosphere. During periods of northward IMF, this transport is sufficient to generate a cold, dense plasma sheet on time scales consistent with satellite observations. However, when the length scales of these narrow current layers approach the ion inertia scale, the MHD approximation is not valid anymore and the Hall …

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