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X-ray emission from the planetary nebula NGC 1360
Jansen, F. A.; McKechnie, S. P.; de Korte, P. A. J. +1 more
The EXOSAT observatory has detected the nucleus of NGC 1360 in four photometric energy bands. The data rules out that the emission is from blackbody origin. Initial fits made with LTE model atmosphere spectra require the presence of highly ionized Oxygen and Neon in the stellar atmosphere.
The in-orbit performance of the Exosat gas scintillation proportional counter
Manzo, G.; Taylor, B. G.; Peacock, A. +2 more
The European X-ray observatory satellite Exosat, launched in May 1983, carries a scientific payload of four instruments designed to study the properties of cosmic X-ray sources. The present investigation is concerned with one of these instruments, taking into account the gas scintillation proportional counter (GSPC) spectrometer. Attention is give…
The Lyman alpha emission in W Ursae Majoris.
Whelan, J. A. J.; Vilhu, O.; Rucinski, S. M.
The paper presents results of reductions of six low resolution IUE-SWP spectra properly exposed at Ly-alpha during one orbital revolution of WUMa, the prototype for late-type contact binaries. Two different methods have been used to eliminate the geocoronal contribution to the emission line. The effect of the interstellar H I absorption has been m…
The ultraviolet variability of the BL Lacertae object OJ 287.
Coe, M. J.; Hanson, C. G.
The International Ultraviolet Explorer (IUE) satellite has been used to observe the BL Lacertae object, OJ287, at 26 epochs between 1978 May and 1984 May. These observations how large and often rapid variations in both the intensity and the spectral slope of the UV continuum. In general, the changes in intensity show little or no correlation with …
Ultraviolet studies of stars in the populous cluster NGC 2100 in the Large Magellanic Cloud.
Bohm-Vitense, E.; Proffitt, C.; Hodge, P.
The authors have studied the ultraviolet energy distributions of the B stars in the LMC cluster NGC 2100. The ultraviolet extinction law was studied for the LMC cluster. The Teff-luminosity diagrams were determined. The brightest stars in the clusters are evolved stars on the "horizontal" supergiant branch. No P Cygni profiles indicatin…
Hard X-Ray Observations of the Eclipsing Binary Ex-Hydrae
Beuermann, K.; Osborne, J.
The authors present light curves of EX Hydrae in the 1 - 10 keV range obtained with the medium energy experiment of EXOSAT. The 67-min modulation was observed with a peak-to-peak amplitude of 36% in the 1 - 4 keV range and of 24% in the 4 - 9 keV range. Newly discovered was a partial X-ray eclipse of ≡3 min full width which coincides with the opti…
X-ray luminosity and the hydrogen-line ratios of quasars and Seyfert galaxies.
Kriss, G. A.
New observations of the Ly-alpha/H-alpha ratio in a set of X-ray-selected active galactic nuclei and an archival study of International Ultraviolet Explorer (IUE) observations of Ly-alpha in low-redshift quasars and Seyfert galaxies have been used to form a large sample (49 objects) for studying the influence of soft X-rays on the enhancement of B…
Two-phase ultraviolet spectrophotometry of the pulsating white dwarf ZZ Piscium.
Holm, A. V.; Bond, H. E.; Panek, R. J. +3 more
Spectra of the pulsating white dwarf ZZ Psc (= G29-38) were obtained using the International Ultraviolet Explorer. By using a multiple-exposure technique in conjunction with simultaneous ground-based exposure-metering photometry, it was possible to obtain mean on-pulse and off-pulse spectra in the 1950-1310 A wavelength range. The ratio of the tim…
Variable, optically thick plasma in the interacting binaries R Arae and HD 207739.
Kondo, Y.; Parsons, S. B.; McCluskey, G. E., Jr.
Two close binaries observed with the IUE, R Ara and HD 207739, exhibit strong variations of spectral energy distribution that indicate the presence of variable, optically thick extrastellar gas. The deepening of the secondary (eclipse-like) minimum toward shorter wavelengths observed in the ultraviolet light curves of R Ara also provides additiona…
C IV and SI IV in the interstellar medium.
de Jong, T.; de Kool, M.
Column-densities are presented of C IV and Si IV along the line of sight to 49 galactic O-stars, derived from IUE spectra. Since these column-densities appear to be uncorrelated with the distance to the background star a truly interstellar origin of these lines can be ruled out. The fact that large column-densities are preferentially observed towa…