Search Publications
The Unusual Dust-Scattering Properties in the Reflection Nebula CED 201
Bohlin, R. C.; Witt, A. N.; Stecher, T. P. +1 more
Spectrophotometric data available from ground-based and IUE observations of the reflection nebula CED 201 and its illuminating star BD + 69.1231 deg are analyzed to deduce the most likely star-nebula geometry and the wavelength dependence of the scattering characteristics of the nebular grains. The dust albedo is found to decline from 0.72 at V to…
Further Observations of the Peculiar Hot Helium-rich Degenerate KPD 0005+5106
Sion, Edward M.; Holberg, J. B.; Liebert, James +1 more
A variety of new ultraviolet and optical spectroscopic observations of the peculiar, hot, helium-rich degenerate KPD 0005+5106 are presented. While the expected lines of helium appear, the only detected transitions from a heavier element assignable to the stellar photosphere is the N V 1240 Å doublet, from which an atmospheric abundance is derived…
Ultraviolet Doubly Excited Fe II Lines in the Laboratory and in the A-Type Star 21 Pegasi
Johansson, S.; Baschek, B.; Brage, T. +2 more
During a new investigation of the UV hollow-cathode spectrum of iron, some 120 lines were identified, among them strong lines around 1850 A, as transitions from doubly excited levels in Fe II. A combination of selective population by charge-transfer processes in the laboratory source and of a strong configuration interaction is probably the cause …
Low-Energy X-Ray Observations of the Wolf 630 System
Johnson, Hugh M.
The septuplet of M dwarfs is resolved into three components, Wolf 630ABab, Wolf 629ab, and VB 8AB, with the EXOSAT channel multiplier array (CMA). W 630 and VB 8 have previously been observed with the Einstein high resolution imager (HRI). The ratio of CMA to HRI count rates for VB 8 can be produced with an isothermal plasma model temperature T = …
Atmospheric Eclipses in the SMC Wolf-Rayet Eclipsing Binary HD 5980: The Heavy versus the Light Metal Abundance
Koenigsberger, G.; Auer, L. H.; Moffat, A. F. J.
Phase-dependent variations in the IUE spectra of the SMC 19.6-day eclipsing binary system HD 5980 (WN4 + 07I) are discussed. The effects of selective atmospheric eclipses in the N, C, and He lines of HD 5980 are found to be similar to those observed in its Galactic counterpart, while the variations in the 1350-1490 A continuum region are virtually…
Rapid Variability of P Cygni Lines in Massive X-Ray Binaries
Voit, G. Mark; Kallman, Timothy R.; McCray, Richard
In early-type X-ray binaries, the recombination time scales for ions such as C IV, Si IV, and N V in the stellar winds of their massive OB companion stars can be very short compared to typical X-ray pulsation or fluctuation time scales. Thus, the authors predict that the 'bleached zones', in which these ions are removed from the stellar wind by X-…
A Flare Event on the Long-Period RS Canum Venaticorum System IM Pegasi
Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W.
The characteristics of a flare event detected on the long-period RS CVn system IM Pegasi are reported. The low-resolution spectrum show enhancements of up to a factor of five in some emission lines. All of the ultraviolet emission lines normally visible are enhanced significantly more than the normal 30 rotational modulation. Emission fluxes of bo…
An IUE Survey of Activity in Red Giants and Supergiants
Gibson, D. M.; Oznovich, I.
Chromospheric and transition region line activity is examined in apparently single red giants and supergiants using the IUE archives. Low-resolution, large-aperture spectra (mostly short-wavelength) were used to search for variations of emission-line fluxes in time. A series of automatic processing procedures were implemented in order to uniformly…
Identification of Lines in the Satellite Ultraviolet: The Spectrum of Tau Scorpii
Cowley, Charles R.; Merritt, Donald R.
The method of wavelength coincidence statistics (WCS) is applied to the ultraviolet spectra of Tau Sco obtained by the IUE. No identifications of elements heavier than Zn were made. With the exception of Zn IV, all identifications had been previously made in an exhaustive study of Copernicus spectra by Rogerson and Ewell (1985). A comparison of th…
Determination of Photospheric Helium Abundances for the Hot White Dwarfs LB 1663 and CD -38 degrees 10980 from EXOSAT Soft X-Ray Photometry
Heise, J.; Kahn, S. M.; Paerels, F. B. S. +1 more
The photospheric soft X-ray emission of hot (Te> 20,000 K) DA white dwarfs is very sensitive to the composition of the stars' atmospheres. Very small amounts of helium in a hydrogen-dominated atmosphere, amounts which are difficult or impossible to measure at UV and optical wavelengths, can be detected in the soft X-ray band. In this…