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On the Nature of the Symbiotic Binary CI Cygni
Stencel, R. E.; Kenyon, S. J.; Garcia, M. R. +4 more
An analysis of ultraviolet and optical spectroscopy is presented for the symbiotic binary CI Cyg. This system contains an M5 II asymptotic branch giant Mg of about 1.5 solar mass, transfering material at a few times 0.00001 solar mass/yr into a large accretion disk surrounding a main-sequence star with Mh of about 0.5 solar mass. A boundary layer …
The Postcollapse Core of M15 Imaged with the HST Planetary Camera
Schneider, Donald P.; Lauer, Tod R.; Faber, S. M. +12 more
It is shown here that, despite the severe spherical aberration present in the HST, the Wide Field/Planetary Camera (WFPC) images still present useful high-resolution information on M15, the classic candidate for a cluster with a collapsed core. The stars in M15 have been resolved down to the main-sequence turnoff and have been subtracted from the …
Empirical velocity laws for cool giants. I. The symbiotic binary EG Andromedae.
Vogel, M.
An empirical velocity law is presented for the wind of a cool giant. The analysis is performed for the symbiotic binary EG And. The system consists of an M2.4 III giant and a hot subdwarf. The UV radiation of the compact hot component is Rayleigh-scattered in the wind of the cool giant. The column density for Rayleigh scattering varies with the or…
First Results from the Goddard High-Resolution Spectrograph: High-Resolution Observations of the 1942 Angstrom Resonance Line of HG II in the Chemically Peculiar B Star, chi LUPI
Wahlgren, Glenn M.; Leckrone, David S.; Johansson, Sveneric G.
The Goddard High-Resolution Spectrograph on the HST has been used to obtain high S/N observations of the sharp-lined, Hg- and Pt-rich B-type star, Chi Lupi, with a resolving power of 87,000. The observations reveal a level of spectroscopic detail never before observed at ultraviolet wavelengths for any star other than the sun. Concentrating on the…
Observations of Scorpius X-1 with IUE: Ultraviolet Results from a Multiwavelength Campaign
Raymond, J. C.; Lewin, W. H. G.; Mitsuda, K. +5 more
IUE UV results are presented for the low-mass X-ray binary Sco X-1. Models that predict UV continuum emission from the X-ray-heated surface from the companion star and from an X-ray illuminated accretion disk are adjusted for parameters intrinsic to Sco X-1, and fitted to the data. X-ray heating is found to be the dominant source of UV emission; t…
The Core of the Nearby S0 Galaxy NGC 7457 Imaged with the HST Planetary Camera
Lauer, Tod R.; Faber, S. M.; Currie, Douglas G. +12 more
We have observed the nearby S0 galaxy NGC 7457 with the Planetary Camera of the Hubble Space Telescope. Spatial structure is observable at the diffraction-limited resolution of the 2.4 m HST primary despite the effects of spherical aberration. The central distribution of starlight appears consistent with a γ ~ -1.0 power law for r < 600 pc, plu…
Variability of the post-AGB star HR 4049 : dust obscuration in a binary system.
Waters, L. B. F. M.; Ferlet, R.; Vidal-Madjar, A. +5 more
Results obtained from a large number of coordinated photometric and spectroscopic observations lead to the conclusion that HR 4049 is a binary with an orbital period near 434 days and a companion of similar mass which either is a white dwarf or a main-sequence star, more likely the second. The H-alpha line is in emission with either a P Cygni prof…
The Onset of Chromospheric Activity among the A and F Stars
Simon, Theodore; Landsman, Wayne
Results are reported from a search for an upper boundary for the onset of main-sequence star activity based on a quest for high-temperature UV line emission in a large collection of IUE spectra. It is shown that strong chromospheric emission is common among early F dwarf and subgiant stars. At its brightest, the emission is equal to that of the mo…
Shot Model Parameters for Cygnus X-1 through Phase Portrait Fitting
Swank, J. H.; Szymkowiak, A. E.; Lochner, James C.
Shot models for systems having about 1/f power density spectrum are developed by utilizing a distribution of shot durations. Parameters of the distribution are determined by fitting the power spectrum either with analytic forms for the spectrum of a shot model with a given shot profile, or with the spectrum derived from numerical realizations of t…
Absolute Extinction and the Influence of Environment: Dark Cloud Sight Lines Toward VCT 10, 30, and Walker 67
Clayton, Geoffrey C.; Cardelli, Jason A.
The range of validity of the average absolute extinction law (AAEL) proposed by Cardelli et al. (1988 and 1989) is investigated, combining published visible and NIR data with IUE UV observations for three lines of sight through dense dark cloud environments with high values of total-to-selective extinction. The characteristics of the data sets and…