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A White Dwarf Companion to the Main-Sequence Star 4 O 1 Orionis and the Binary Hypothesis for the Origin of Peculiar Red Giants
Johnson, Hollis R.; Ake, Thomas B.
In the course of an investigation with the IUE satellite of the ultraviolet spectra of peculiar red giants, the authors have discovered a white dwarf companion to the MS star 4 ο1Ori. They discuss the reductions performed for the ο1Ori IUE observations, and compare these with field white dwarfs to derive parameters of the whi…
The High-Resolution Soft X-Ray Spectrum of HZ 43. II. Bolometric X-Ray Flux, Effective Temperature, and Radius
Heise, J.; Bleeker, J. A. M.; Brinkman, A. C. +1 more
The authors present a reanalysis of the high-resolution soft X-ray spectrum of HZ 43, obtained with the 500 lines mm-1 transmission grating spectrometer on EXOSAT. They show here that the estimates of Te and log g from the shape of the X-ray spectrum depend critically on the code used to generate the model spectra, but that t…
The Outer Atmospheres of the Coolest M Giants: Ultraviolet Spectra of rho Persei, 2 Centauri, G Herculis, theta Apodis, and R Lyrae
Johnson, Hollis R.; Eaton, Joel A.
High-dispersion IUE spectra of five M giants (spectral type M4 - M7) are discussed. Most of the emission lines and stronger absorption lines are identified for ρ Per in the wavelength range λλ2320 - 3030. The chromospheric spectra of ρ Per, R Lyr, 2 Cen, and g Her are remarkably similar, both among themselves and with respect to stars of earlier s…
Observations of the Late Superhump in VW Hydri
Motch, C.; Beuermann, K.; van Paradijs, J. +2 more
This paper presents the results of simultaneous optical and near-IR photometry, optical fast spectroscopy, and Exosat X-ray observations of the dwarf nova VW Hyi, obtained simultaneously during three consecutive orbital cycles, approximately two days after the 1983 November superoutburst terminated. The optical data show clear evidence for a 'late…
Eight Years of Ultraviolet Spectra of the Variable BL Lacertae Object PKS 2155-305
Kondo, Y.; Urry, C. M.; Hackney, K. R. H. +1 more
The brightest known BL Lacertae object at ultraviolet wavelengths is PKS 2155-304, which was discovered as a result of its strong X-ray emission. Since 1979, 64 ultraviolet spectra of this object have been obtained with the International Ultraviolet Explorer (IUE) satellite. These have been analyzed in a consistent fashion using Gaussian extractio…
The C IV Doublet Ratio Intensity Effect in Symbiotic Stars
Altamore, A.; Kafatos, M.; Michalitsianos, A. G. +3 more
High-resolution UV spectra in the 1200-2000 wavelength range of the symbiotic variable R Aqr and its nebular jet were obtained in July 1987 with the IUE. The line profile structure of the C IV 1548, 1550 doublet in the jet indicates multicomponent velocity structure from an optically thin emitting gas. The C IV doublet profiles in the compact H II…
The High-Resolution Photospheric Soft X-Ray Spectrum of Sirius B
Heise, J.; Bleeker, J. A. M.; Brinkman, A. C. +1 more
The authors present the high-resolution soft X-ray spectrum of the hot white dwarf Sirius B, as measured with the 500 lines mm-1 transmission grating spectrometer on EXOSAT. The X-rays are of purely photospheric origin. Using a large grid of model atmospheres, the authors determine the effective temperature of Sirius B with high accurac…
Simultaneous EXOSAT and VLA Observations of the Contact Binaries VW Cephei and XY Leonis: Quiescent Emission and a Flare on VW Cephei
Heise, John; Vilhu, Osmi; Caillault, Jean-Pierre
Two W UMa-type contact binaries, XY Leo and VW Cep, were observed simultaneously with Exosat, the VLA, and, in the case of XY Leo, optically. The temporal coverage of each star was sufficient to monitor them throughout two orbital revolutions (P about 0.27 days); however, no orbital modulation of either the X-ray or 6 cm data was seen for either s…
EXOSAT Observations of the TYCHO Supernova Remnant
Robba, N. R.; Taylor, B. G.; Smith, A. +3 more
The Gas Scintillation Proportional Counter and the Medium Energy Instruments on board EXOSAT were used to measure the X-ray spectrum of the Tycho supernova remnant over the range 1.5 - 10 keV. The emission lines due to S, Ar, Ca, and Fe (≡6.48 keV) are clearly resolved from the underlying continuum which is measured to have a temperature of 6.5±0.…
Indirect IUE Observations of O VI from Photoexcited Fluorescence Lines of Fe ii, Present in the Spectrum of RR Telescopii
Johansson, Sveneric
A new, highly excited level of Fe II at 13.7 eV has been established by means of six lines in the laboratory spectrum below 2000 Å. Confirming transitions appear in the infrared region. Four of the ultraviolet lines coincide with previously unidentified lines in the IUE spectrum of RR Tel reported by Penston et al. (1983). One of the remaining UV …