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Abundance analysis from the UV spectrum of the He-w star HR 6000.
Hack, M.; Castelli, F.; Morossi, C. +1 more
A high resolution spectrum of the He-w star HR 6000, covering the SW and LW regions, has been analyzed. A fully line-blanketed model atmosphere with parameters T(e) = 14,000 K, log g = 4, microturbulence xi = 2 km/s has been adopted. This model is in agreement with the photometric data and yields the same abundance for the Fe II and Fe III ions. B…
On the ultraviolet iron spectrum of pre-white dwarfs.
Drilling, J. S.; Schoenberner, D.
The authors have detected numerous lines of Fe V, Fe VI, and Fe VII in high-resolution IUE spectra of two central stars and a number of very hot subdwarfs. The strengths of these lines vary widely from star to star, suggesting that the abundance of iron in the atmospheres of the immediate progenitors of white dwarfs in strongly variable. A possibl…
KPD 0005+5106 : a post-PG 1159 type object ?
Margon, B.; Downes, R. A.; Liebert, J.
In a survey for galactic plane UV-excess objects, a very hot (T about 100,000 K) helium-rich white dwarf is discovered. The object is spectroscopically similar to the pulsating PG 1159 class of stars, with narrow emission lines of He II, probably C IV, and possibly C III/N III, although there is no trace of carbon absorptions. Not all features hav…
A search for diffuse interstellar bands in the ultraviolet.
Snow, T. P., Jr.; Seab, C. G.
The International Ultraviolet Explorer (IUE) Satellite was used to collect interstellar extinction curves for 58 moderately reddened lines of sight. Spectral types of the background stars ranged from O7 to A0. All luminosity classes are represented, but early B main-sequence stars predominate. E(B-V) reddening values ranged from 0.14 to 1.13 mag, …
IUE and optical spectral scans of U Sagittae : an analysis and comparison with U Cephei.
Plavec, M. J.; Dobias, J. J.
Recent optical and ultraviolet observations of U Sge are presented, and the results are compared with observations of U Cephei. The observations were carried out with: the International Ultraviolet Explorer (IUE) satellite; with the ITS scanner of the Lick Observatory; and with a Varo image-tube camera attached to a coude spectrograph. Comparison …
X-Ray Spectral Variability of 3C273
Molteni, D.; Staubert, R.; Turner, M. J. L. +2 more
3C273 has been monitored by EXOSAT over the period December 1983 to June 1984 in 4 observations. In the December observation the flux was high and the spectrum showed a power law index of 1.5 changing to 0.9 at∼8 keV. In subsequent observations the flux dropped to∼40% of its original value and the hard tail disappeared. In the last observation the…
IUE results on the AM Herculis stars CW 1103, E 1114 and PG 1550.
Szkody, P.; Panek, R. J.; Liebert, J.
IUE data are presented on three AM Her stars (CW 1103 + 254, E1114 + 182, and PG 1550 + 191) which are used in conjunction with optical and IR fluxes to study the accretion characteristics of these systems in relation to other polars.The time-resolved IUE spectra of CW 1103 show that the column contributes little to the UV, while the white dwarf, …
The galactic gamma-ray distribution - Implications for galactic structure and the radial cosmic-ray gradient
Harding, A. K.; Stecker, F. W.
The radial distribution of gamma ray emissivity in the Galaxy was derived from flux longitude profiles, using both the final SAS-2 results and the recently corrected COS-B results and analyzing the northern and southern galactic regions separately. The recent CO surveys of the Southern Hemisphere were used in conjunction with the Northern Hemisphe…
Analysis of ultraviolet atmospheric eclipses in the Wolf-Rayet binaryCV Serpentis.
Cherepashchuk, A. M.; Eaton, J. A.; Khaliullin, Kh. F.
The authors have obtained ultraviolet spectra covering one-half of an orbital cycle of CV Ser. Marked phase effects have been detected in which ultraviolet absorption lines are greatly strengthened when the W-R star is in front. No eclipses are seen longward of 2300 Å, while below 2000 Å blanketing by numerous lines, spread out in frequency by the…
Cepheid distances from blue main-sequence companions.
Bohm-Vitense, E.
The author determines the absolute visual magnitudes of main-sequence Cepheid companions from their effective temperatures. These are obtained by comparing the measured relative energy distributions with model atmosphere energy distributions. Assuming an average galactic extinction law, it is found that the distance moduli for the Cepheids should …