Search Publications
The Accretion Disk and White Dwarf during the Quiescence of the Dwarf Novae VW Vulpeculae and χ Leonis
Sion, Edward M.; Henry, Colleen K.
We have carried out an International Ultraviolet Explorer archival comparative study of the two U Geminorum type dwarf novae VW Vulpeculae and χ Leonis. The spectrum of χ Leo does not show any C IV, a feature normally seen in the vast majority of other dwarf novae. For VW Vul, a single-temperature high-gravity photosphere does not produce a consis…
The Orbit and Spectral Line Variations of the Massive Binary HD 163181 (V453 Scorpii)
Wang, Z.; Gies, D. R.; Bagnuolo, W. G., Jr. +3 more
We present revised orbital elements for the massive interacting binary HD 163181, and we offer the first evidence of apsidal motion in the orbit (apsidal period U=510+/-100 yr). We searched for but found no obvious evidence of the secondary's spectral lines in our optical spectra. We do observe, however, systematic profile variations with orbital …
The Confusion Limit on Astrometry with the Space Interferometry Mission
Böker, Torsten; Allen, Ronald J.; Rajagopal, Jayadev
An important requirement for the Space Interferometry Mission (SIM) is to carry out precision astrometry in crowded fields. This capability is crucial, for example, to accurately measure proper motions of bright stars in nearby galaxies. From such measurements, one can obtain distance estimates, explore the dynamics of these systems, and measure t…
The 3-D Heliosphere at Solar Maximum
Marsden, Richard G.
Conference was held in Noordwijk, Netherlands, in 2000 October. Proceedings will be edited by R. G. Marsden and published in Space Science Reviews.
A Study of the Wavelength Calibration of NEWSIPS High-Dispersion Spectra
Smith, Myron A.
In this study we cross-correlate many IUE echellograms of a variety of well-observed stars to evaluate systematic error sources in the wavelength zero points (velocities) of all three cameras. We first evaluate differences between the final archived (``NEWSIPS'') and the originally processed (``IUESIPS'') echellograms. These show a marked time dep…
The Underlying White Dwarf Accretor in the Dwarf Nova UU Aquilae
Sion, Edward M.; Stump, Michael
We present a high-gravity, solar composition model atmosphere and model accretion disk study of the U Gem type dwarf nova UU Aql. We have identified the far-UV signature of the underlying white dwarf for the first time. Our best-fit model atmosphere to the observed far-UV spectrum in quiescence is 27,000+/-1000 K. The solar abundance high-gravity …
A Large Spectral Class Dependence of the Wilson-Bappu Effect among Luminous Stars
Parsons, Sidney B.
The striking correlation between Ca II K-line emission width and absolute visual magnitude has not previously been well calibrated for stars more luminous than giants. From a sample of binary systems fit to isochrones, we find deviations of more than 2 mag, correlated with spectral class, between these binarity Mv values and the Wilson-…
Properties of PACE-I HgCdTe Detectors in Space: The NICMOS Warm-Up Monitoring Program
Nota, A.; Calzetti, D.; Böker, T. +13 more
We summarize the results of a monitoring program which was executed following the cryogen exhaustion of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on board the Hubble Space Telescope. During the subsequent warm-up, detector parameters such as detective quantum efficiency, dark current, bias offsets, and saturation levels have …
WFPC2 Stellar Photometry with HSTPHOT
Dolphin, Andrew E.
HSTphot, a photometry package designed to handle the undersampled point-spread functions (PSFs) found in WFPC2 images, is introduced and described, as well as some of the considerations that have to be made in order to obtain accurate PSF-fitting stellar photometry with WFPC2 data. Tests of HSTphot's internal reliability are made using multiple ob…
Toward High-Precision Astrometry with WFPC2. I. Deriving an Accurate Point-Spread Function
Anderson, Jay; King, Ivan R.
The first step toward doing high-precision astrometry is the measurement of individual stars in individual images, a step that is fraught with dangers when the images are undersampled. The key to avoiding systematic positional error in undersampled images is to determine an extremely accurate point-spread function (PSF). We apply the concept of th…