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Aerospace, Physics, and Space Science Faculty Publications

Articles 271 - 282 of 282

Full-Text Articles in Astrophysics and Astronomy

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xii. Ground-Based Monitoring Of 3c 390.3, Matthias Dietrich, T. D. Oswalt, Jun Tao Jan 1998

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xii. Ground-Based Monitoring Of 3c 390.3, Matthias Dietrich, T. D. Oswalt, Jun Tao

Aerospace, Physics, and Space Science Faculty Publications

Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux Fλ(5177 Å), and the integrated emission-line fluxes of Hα, Hβ, Hγ, He II λ15876, and He II A4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000 Å). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the cross-correlation functions, typically around 5 days, but with uncertainties …

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White Dwarfs In Globular Clusters: Hubble Space Telescope Observations Of M4, Harvey B. Richer, Matt A. Wood Aug 1997

White Dwarfs In Globular Clusters: Hubble Space Telescope Observations Of M4, Harvey B. Richer, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

Using WFPC2 on the Hubble Space Telescope, we have isolated a sample of 258 white dwarfs (WDs) in the Galactic globular cluster M4. Fields at three radial distances from the cluster center were observed, and sizable WD populations were found in all three. The location of these WDs in the color-magnitude diagram, their mean mass of 0.51(±0.03) M⊙, and their luminosity function confirm basic tenets of stellar evolution theory and support the results from current WD cooling theory. The WDs are used to extend the cluster main-sequence mass function upward to stars that have already completed their nuclear evolution. The …

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Whole Earth Telescope Observations Of The Helium Interacting Binary Pg 1346+082 (Cr Bootis), Judith L. Provençal, Matt A. Wood May 1997

Whole Earth Telescope Observations Of The Helium Interacting Binary Pg 1346+082 (Cr Bootis), Judith L. Provençal, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

We present our analysis of 240 hr of white-light, high-speed photometry of the dwarf nova-like helium variable PG 1346+082 (CR Boo). We identify two frequencies in the low-state power spectrum, at 679.670 ± 0.004 μHz and 669.887 ± 0.008 μHz. The 679.670 μHz variation is coherent over at least a 2 week time span, the first demonstration of a phase-coherent photometric variation in any dwarf nova-like interacting binary white dwarf system. The high-state power spectrum contains a complex fundamental with a frequency similar, but not identical, to the low-state spectrum, and a series of harmonics not detected in low state. …

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Design Considerations For A Small Ultraviolet-Visible Space Telescope For Amateur And Professional Use, Donald Platt Jan 1997

Design Considerations For A Small Ultraviolet-Visible Space Telescope For Amateur And Professional Use, Donald Platt

Aerospace, Physics, and Space Science Faculty Publications

Presented is a preliminary design for a small ultraviolet- visible (uv-vis) sensitive space telescope. Included will be optical, sensor, and spacecraft subsystem design considerations. With recent advances in charge coupled device (CCD) technology it is now possible to build a space telescope system with wavelength sensitivity from 200 to 1000 nm. A main objective of this design is to keep costs to a minimum and use commercial off the shelf (COTS) components wherever possible. Such a low-cost system could provide a platform for studying such untested techniques as small space-based optical interferometry. The observatory could be open to a guest …

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The Δ Scuti Star Fg Virginis Ii. A Search For High Pulsation Frequencies, Michel Breger, Matt A. Wood Jan 1996

The Δ Scuti Star Fg Virginis Ii. A Search For High Pulsation Frequencies, Michel Breger, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

Although the δ Scuti and roAp variables occupy similar positions on and near the main sequence, δ Scuti variables pulsate with lower radial and nonradial overtones and lower frequencies. To test whether high frequencies (as found in the roAp stars) are also present in δ Scuti stars, a multisite campaign with the Whole Earth Telescope (WET) was carried out for the star FG Vir. The 96.7 hours of WET photometry were supplemented by measurements made with the Delta Scuti Network (DSN), because the DSN technique includes regular measurements of comparison stars and is better suited to monitoring the low frequencies …

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Hubble Space Telescope Observations Of Cool White Dwarf Stars: Detection Of New Species Of Heavy Elements, Harry Shipman, Terry D. Oswalt Mar 1995

Hubble Space Telescope Observations Of Cool White Dwarf Stars: Detection Of New Species Of Heavy Elements, Harry Shipman, Terry D. Oswalt

Aerospace, Physics, and Space Science Faculty Publications

Observations of cool white dwarf stars with the Hubble Space Telescope has uncovered a number of spectral features from previously unobserved species. In this paper we present the data on four cool white dwarfs. We present line identifications, equivalent width measurements, and brief summaries of the significance of our findings. The four stars observed are GD 40 (DBZ3), G 74-7 (DAZ), L 745-46A (DZ), and LDS 749 B (DBA). Many additional species of heavy elements were detected in GD 40 and G 74-7. In L 745-46A,while the detections are limited to Fe I, Fe II, and Mg II, the quality …

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Effects Of Aberrations On Spatially Modulated Fourier Transform Spectrometers, R Glenn Sellar, James Bruce Rafert Sep 1994

Effects Of Aberrations On Spatially Modulated Fourier Transform Spectrometers, R Glenn Sellar, James Bruce Rafert

Aerospace, Physics, and Space Science Faculty Publications

Spatially modulated Fourier transform spectrometers (FTS) have a throughput advantage over dispersive spectrometers, since an FTS does not require a slit in order to achieve spectral resolution. The traditional implementation of FTSs employs a scanning Michelson interferometer, but since this interferometer is temporally modulated, it is difficult or impossible to use with a target whose spatial and/or spectral signature is changing rapidly. The less common spatially modulated approach to FTS allows all spectral channels to be acquired simultaneously, but cylindrical optics are required to create an imaging version a FTS (IFTS). This combination of cylindrical and spherical optics, used to …

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Simultaneous Light And Radial Velocity Curve Solutions For U Cephei, James Bruce Rafert, N L. Markworth Aug 1991

Simultaneous Light And Radial Velocity Curve Solutions For U Cephei, James Bruce Rafert, N L. Markworth

Aerospace, Physics, and Space Science Faculty Publications

The light-curve synthesis approach of Wilson & Devinney has been used to solve simultaneously light and radial velocity curves of the Algol-type eclipsing binary star U Cephei. We have performed eight new differential corrections solutions using the photometric data of Markworth and the radial velocity data of Batten to obtain a consistent set of orbital and astrophysical parameters for the light and velocity curves of this famous system. We find U Cephei to be best modeled using the semidetached (mode 5) system geometry of the Wilson & Devinney program, with a primary rotating at about 5.2 times its synchronous rate, …

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The Physical Properties Of Double Degenerate Common Proper Motion Binaries, Edward M. Sion, Terry D. Oswalt, James Liebert, Paul Hintsen Apr 1991

The Physical Properties Of Double Degenerate Common Proper Motion Binaries, Edward M. Sion, Terry D. Oswalt, James Liebert, Paul Hintsen

Aerospace, Physics, and Space Science Faculty Publications

We present spectral types and spectrophotometry for 21 double degenerate (DD) common proper motion binaries and provide estimates of their colors, absolute visual and bolometric magnitudes, and cooling ages. The most typical double degenerate pair contains stars of similar color and spectral type, with an average Mv = 14.20, and average cooling age of ≈3×10⁹ yr, thus typically belonging to the extremely old disk population subcomponent. The oldest pairs in the sample are 9 × 10⁹ yr. The differential cooling ages, Δ log τc, range between 0.01 and 0.84, with the most typical pair having Δ log τc = 0.30, …

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Uv Observations Of The Cool Dbqa5 White Dwarf Lds 678a: Limits On The Atmospheric Composition, Pressure Shift, And Gravitational Redshift Derived From C I 2479, Terry D. Oswalt, Edward M. Sion, Gordon Hammond, James W. Liebert, Gary Wegner, Detlev Koester, Pamela M. Marcum Feb 1991

Uv Observations Of The Cool Dbqa5 White Dwarf Lds 678a: Limits On The Atmospheric Composition, Pressure Shift, And Gravitational Redshift Derived From C I 2479, Terry D. Oswalt, Edward M. Sion, Gordon Hammond, James W. Liebert, Gary Wegner, Detlev Koester, Pamela M. Marcum

Aerospace, Physics, and Space Science Faculty Publications

We present a high-resolution ultraviolet spectrum of the helium-rich degenerate LDS 678A, obtained with the International Ultraviolet Explorer (IUE) satellite. LDS 678A is the coolest metallic line degenerate (DQ or DZ) yet observed with the IUE echelle. These observations provide a detailed line profile of the strong C I 2479 absorption line and equivalent width W₂₄₇₉ = 2.35 ± 0.06 Å from which theoretical profile fits yield a carbon abundance of log C/He = (-6.7 ± 0.2). The presence of carbon in a Herich atmosphere lends credence to the notion that LDS 678A is a transitional case between the DB …

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Four Short-Period Algols, James Bruce Rafert Oct 1990

Four Short-Period Algols, James Bruce Rafert

Aerospace, Physics, and Space Science Faculty Publications

We have analyzed the light curves of four close binary star systems (BV 267, RU UMi, XZ CMi, and VV UMa) using the Wilson-Devinney differential corrections model. The present system geometries of these binaries is that of short-period, semi-detached systems with Roche lobe filling secondaries and main-sequence primaries. Differential coordinates in the mass-luminosity and mass-radius diagrams indicate that the secondary components lie near the main sequence, except in the case of BV 267. It is suggested that these systems are binaries with slightly overluminous and over-sized secondaries which have undergone case A mass transfer. This contention is supported by timing …

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One-Dimensional Three-Body Scattering Problem Used As A Testing Ground For The K-Matrix Method For Scattering Reactions Of Complex Systems, D. Rodjak, William Tobocman, Gaurav K. Tandon Oct 1972

One-Dimensional Three-Body Scattering Problem Used As A Testing Ground For The K-Matrix Method For Scattering Reactions Of Complex Systems, D. Rodjak, William Tobocman, Gaurav K. Tandon

Aerospace, Physics, and Space Science Faculty Publications

The scattering reactions of three equal-mass particles constrained to move in a straight line and interacting with each other via zero-range potentials have been analyzed on the basis of the extended R-matrix theory. The simplicity of the model facilitates an exposition of the complexities that result from the existence of rearrangement channels and from the possibility for breakup into three-body channels. The conventional expressions for the K matrix and the T matrix are derived on a rigorous basis. A practical method for approximating the continuum of three-body breakup channels by a discrete set is used to carry out a distorted-wave …

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