Search Publications
The (C III lambda 1909/Si III lambda 1892) Ratio as a Diagnostic for Planetary Nebulae and Symbiotic Stars
Feibelman, Walter A.; Aller, Lawrence H.
Suitable IUE archival material on planetary nebulae has been examined to determine the log R /F(lambda 1909 C III)/F(lambda 1892 Si III)/ as a discriminant for distinguishing planetary nebulae from symbiotic stars and related objects. The mean value of log R for 73 galactic planetaries is 1.4, while that of extragalactic planetaries appears to be …
Deterministic Chaos in Accreting Systems: Analysis of the X-Ray Variability of Herculis X-1
Voges, W.; Atmanspacher, H.; Scheingraber, H.
The irregular X-ray variability of Her X-1 has been investigated in different phases of the 1.7 day orbital period of the binary system Her X-1/HZ Her. The analyzed data have been sampled by the Exosat satellite during two main-on states of the 35 day cycle of the system. Using new system theoretical methods, the attractors of different processes …
The Fading of the Narrow-Line Region in 3C 390.3
Clavel, J.; Wamsteker, W.
IUE spectra of 3C 390.3 obtained at 17 different epochs from 1978 to 1986 show that the flux in the narrow core of the Ly-alpha 1216 A and C IV 1550 A emission lines steadily declined by a factor of 1.7 and 3.2, respectively. Lloyd's optical monitoring reported in 1984 shows that the continuum intensity decreased by 2 mag over the years 1968-1980.…
A New Soft X-Ray Mode in the AM Herculis Object E2003+225
Mukai, Koji; Treves, Aldo; Maraschi, Laura +3 more
Exosat observations of the AM Her object E2003 + 225 made in June and September 1985, are presented together with optical and ultraviolet observations. The averages of soft X-ray count rate doubled between October 1983 and June 1985; the simultaneously measured V band intensity fell by a factor of 3 and the UV flux by 20 percent. The medium-energy…
The Local Interstellar Medium. VII. The Local Interstellar Wind and Interstellar Material in Front of the Nearby Star alpha Ophiuchi
Frisch, P. C.; York, D. G.; Fowler, J. R.
IUE observations of Mg I λ2852.127 are used to search for warm interstellar gas in the direction of α Oph. Mg I should be a sensitive tracer of warm gas because of dielectronic recombination. However, the authors show that the observed Mg I absorption feature is dominated by material associated with a wisp of relatively cool H I found at the posit…
Mass Distribution and Evolutionary Scheme for Central Stars of Planetary Nebulae
Heap, Sara R.; Augensen, Harry J.
The authors report on a study to determine the mass distribution and evolutionary scheme for planetary nuclei. First, absolute magnitudes were derived from ultraviolet stellar magnitudes for 68 galactic planetaries and three planetaries in the Magellanic Clouds. By comparing the luminosities and ages since the formation of the nebula with evolutio…
Extinction and Abundance Properties of Alpha Scorpii Circumstellar Grains
Buss, Richard H., Jr.; Snow, Theodore P., Jr.; Gilra, D. P. +1 more
The authors have investigated the ultraviolet extinction and element depletions in the circumstellar envelope of the M supergiant binary system, α Sco, by using IUE, Copernicus, and ANS data of the B dwarf companion, α Sco B, which can be seen in absorption through the cool-star envelope. After assessing the interstellar, circumstellar, and atmosp…
The Ultraviolet Spectra of Intermediate-Redshift Quasars. II.
Huggins, P. J.; Kinney, A. L.; Bregman, J. N. +1 more
This paper completes the analysis of an IUE survey of intermediate-redshift QSOs for which the results on Ly-alpha and continuum properties were given previously. The weaker lines were measured and are discussed in the context of an extended sample including Seyfert galaxies and high-redshift QSOs. The EW(C IV) anticorrelates with the luminosity o…
Studies of Hot B Subdwarfs. V. Continuing Investigation of the C, N, and SI Abundance Patterns in the Atmospheres of sdB Stars
Fontaine, G.; Wesemael, F.; Lamontagne, R.
High-dispersion ultraviolet observations of two hot, hydrogen-rich subdwarfs have been obtained with the IUE observatory and are presented. These data are analyzed with model atmosphere techniques, and element abundances for C, N, and Si are derived. Both PG 0342 + 026 (Te = 21,800 K) and PG 1104 + 243 (Te = 27,200 K) display abundances of these i…
The Low-Luminosity X-Ray Sources in Omega Centauri
Bolte, Michael; Margon, Bruce
The authors report multicolor CCD photometry of the fields of three X-ray sources in ω Centauri; two have very accurate (10arcsec) EXOSAT X-ray positions, in addition to observations from the Einstein Observatory. The crowding in these X-ray fields is moderate and does not preclude accurate photometry of individual objects. Although the data in th…