Search Publications
Detection of Neutral Oxygen and Sulfur Emissions near Io Using IUE
Skinner, T. E.; Feldman, P. D.; Moos, H. W. +6 more
Two very long IUE exposures obtained with precise control of the spacecraft pointing show emissions due to neutral oxygen and sulfur near Io. The emitting region is centered on Io and is less than five Io diameters across. The two spectra obtained near eastern and western elongation in 1986 July and October, respectively, are similar, independent …
Ultraviolet Observations of Extensive Variability in the Stellar Wind of ξ Persei
Howarth, Ian D.; Prinja, Raman K.; Henrichs, Huib F.
Fifty-six high-resolution ultraviolet IUE observations of ξ Per [O7.5 III] are presented. The optically thick C IV and N V resonance doublets yield a terminal velocity of v = 2600 km s-1. The spectra reveal dramatic variability in the Si IV P Cygni profiles down to short time scales (≡1 hr). The morphology of the variations is character…
EXOSAT Observations of 4U/MXB 1636-53: On the Relation between the Amount of Accreted Fuel and the Strength of an X-Ray Burst
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +4 more
During EXOSAT observations of 4U/MXB 1636-53 in 1985 August, three bursts were observed in 6 hr and 24 bursts in 79 hr of uninterrupted observing. The persistent X-ray flux varied by about a factor of 2.4, the burst intervals by a factor of 24 (from 35 minutes to 14 hr), and the integrated burst fluxes (the burst fluences), and burst peak fluxes b…
High-Energy Gamma Rays Probing Cosmic-Ray Spectral Differences thoughout the Galaxy
Bloemen, J. B. G. M.
Detailed spectra of the Galactic γ-ray emission (50 MeV-6 GeV) are derived from a combination of all the observations obtained with the COS-B satellite. These spectra indicate that the cosmic-ray (CR) proton spectrum is on average flatter in the outer Galaxy than in the inner Galaxy and locally by approximately ∝ E0.4, and maybe more, s…
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…