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The Properties of OB Supergiants in the Large Magellanic Cloud. I. Energy Distributions of 10 B Supergiants
Fitzpatrick, Edward L.
It is demonstrated here that line-blanketed, LTE plane-parallel model atmosphere calculations provide excellent fits to the energy distributions from the ultraviolet through the visual ranges of B supergiants in the LMC. The models are computed using the atmosphere program of Kurucz (1979) but have been constructed with lower gravities than were c…
Simultaneous Multifrequency Observations of Markarian 421
Brodie, Jean; Bowyer, Stuart; Tennant, Allyn
The highly variable BL Lacertae object Mrk 421 has been observed simultaneously in the radio, optical, ultraviolet, and X-ray bands over a period of 4 days in early 1984 December and once again in early 1985 January. Using the EXOSAT observatory, the authors found that during this time the 2 - 10 keV flux dropped by a factor of 8, whereas the 0.1 …
Spectropscopic Observations of the Symbiotic Binary RW Hydrae
Fernandez-Castro, Telmo; Kenyon, Scott J.
Ultraviolet/optical spectrophotometry and infrared photometry show that the symbiotic binary RW Hya is comprised of an M giant (with L of about 1000 solar luminosities) and a compact object (with L of about 200 solar luminosities) which resembles the central star of a planetary nebula. The luminosity of the hot component is produced by a nuclear s…
EXOSAT and Einstein Observations of the X-Ray Pulsar 4U 1145-619
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +1 more
Results are presented of several Einstein and Exosat X-ray observations of 4U 1145 - 619, an X-ray pulsar orbiting the Be star HD 102567/Hen 715 with marked transient behavior. Pulse-timing analysis of data from imaging instruments on both missions was performed using a period-folding technique, which showed an interesting variation of the light c…
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-…