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Ultraviolet carbon lines in the spectrum of the white dwarf BPM 11668.
Wegner, G.
The southern hemisphere DC white dwarf BPM 11668 has been found to show strong ultraviolet lines of neutral carbon using observations from the IUE satellite. This star seems typical of the growing number of DC white dwarfs found to be of this type and appears to have a carbon abundance near C:He = 10-5 with Teff = 8500K.
The relationship between soft X-rays and the 1640 A feature fluxes inlate-type stars.
Gonzalez-Riestra, R.; Rego, M.; Fernandez-Figueroa, M. J.
The relationship between the soft X-ray flux and the wavelength 1640 feature in a sample of late-type stars is studied. It is assumed that all the observed feature intensity comes from the helium line and that only the fraction of the He II line due to recombination is directly related to the X-ray flux. A close correlation is found between both f…
Quasi-simultaneous optical and UV observations of OJ 287 during an active period in 1983.
Maraschi, L.; Tanzi, E. G.; Falomo, R. +1 more
Far UV spectra (1200 - 3000 Å) of OJ 287 were taken with IUE on Feb. 15th, 1983. Optical spectrophotometry (4500 - 7800 Å) was obtained three days later with the 1.8 m telescope of the Asiago Observatory. The source was in an intermediate state, mV ≅ 14, between quiescence and the maximum reported in January (mV ≅ 13). A powe…
High rotational velocity of a region around the primary of Algol.
Molaro, P.; Cugier, H.
An analysis of the IUE spectra of Algol near λ2800 Å is performed. For this purpose the observations are compared with the calculated synthetic spectra. Significant differences are found. Near Mg II resonance lines, the observed spectra are situated below the calculated ones at the wavelength range from λ2790 Å to λ2807 Å. This local depression is…
IUE observations of the nucleus of the galactic globular cluster NGC 2808.
Caloi, V.; Castellani, V.
The UV spectrum of the nucleus of the galactic globular cluster NGC 2808 shows two distinct components: a point-like one, probably a supra BHB star of about 40,000K in the phase of rapid crossing of the HR diagram from the red giant tip, and a diffuse one, interpreted as a clump of blue HB stars. The contribution of these HB stars produces a clust…
X-ray observations of bright galactic bulge sources in the vicinity of GX 5-1.
van der Klis, M.; Rappaport, S.
Results are presented for 44 d of pointed COS-B X-ray observations of the galactic center region around GX5-1. It is found that GX5-1 exhibits relatively rapid (≡103 s) intensity transitions as well as flaring events with a typical time scale of ≡104 s. Neither GX5-1, GX3+1 nor GX9+1 shows evidence of periodic intensity modul…
A method to improve the visibility of time-variable gamma-ray sources in structured background
Mayer-Hasselwander, H. A.; Oezel, M. E.
For the investigation of time variable gamma-ray sources (e.g. pulsars) embedded in a spatially structured background emission, the spatial selection of those gamma-ray events which are probable to increase the observed signal is not a trivial task. A method is presented which allows for the optimum event selection without introducing any statisti…
Ultraviolet observations of AR Lacertae.
Kiziloglu, U.; Ogelman, H.; Derman, E. +1 more
Short-wavelength (1150-1950 Å) low-resolution and long-wavelength (2000-3000 Å) high-resolution ultraviolet spectra of the RS CVn type binary system AR Lac obtained by IUE are examined. The surface fluxes of short-wavelength chromospheric and transition region lines show average enhancements of 20-200 times to that of the quiet Sun, respectively. …
IUE spectrophotometry of X Persei (4U 0352+30).
Bianchi, L.; Perryman, M. A. C.; Bernacca, P. L. +1 more
Seven low-resolution ultraviolet spectra of X Per obtained with the IUE satellite between March 20 - 29, 1980 are analysed. If the star is a member of the Per OB 2 association, with an assumed distance d = 340 ± 20 pc, it follows that the absolute visual magnitude is Mv = -2.3 ± 0.2, the radius R = (4.1 ± 0.6) R_sun; and the mass is M =…
Superionization in the AOV star HD 119921.
Franco, M.; Molaro, P.; Morossi, C. +1 more
The IUE high-resolution spectrum of the A0 V star HD 119921 is studied. The anomalous presence of superionized elements (C IV, Si IV) is reported. The authors' analysis excludes classification errors or the presence of a hot companion as the source of the C IV and Si IV lines.