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New HST observations of the core of R Aquarii I. Imaging.
Paresce, Francesco; Hack, Warren
The inner region of the symbiotic system R Aquarii was imaged with the Faint Object Camera on the Hubble Space Telescope (HST) in order to determine the source and structure of the highly collimated bipolar jet near the central Mira variable. Coverage over both a wide wavelength and temporal range was ensured by exposures through narrow and medium…
Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra. III. Copper and zinc.
Smith, K. C.
Atmospheric abundances of copper and zinc are derived for a sample of 40 normal, superficially normal, and HgMn-type main-sequence late-B stars by LTE spectrum-synthesis analysis of co-added high-resolution International Ultraviolet Explorer (IUE) spectra. In the normal and superficially normal stars, the abundances of these elements are generally…
Ammonia in comet P/Halley.
Eberhardt, P.; Meier, R.; Krankowsky, D. +1 more
In comet P/Halley the abundances of ammonia relative to water reported in the literature differ by about one order of magnitude from roughly 0.1% up to 2%. Different observational techniques seem to have inherent systematic errors. Using the ion mass channels m/q=19amu/e, 18amu/e and 17amu/e of the Neutral Mass Spectrometer experiment aboard the s…
Abundance analysis of the hot post-AGB star Barnard 29.
Dufton, P. L.; Keenan, F. P.; Conlon, E. S.
We present a model atmosphere analysis for the relatively bright (V~13) globular cluster post-AGB star, Barnard 29, using IUE and high resolution (0.06A FWHM) optical spectra. The derived atmospheric parameters are T_eff_=20000+/-1000K and logg=3.0+/-0.1dex, which imply a current mass of ~0.55Msun_. The chemical composition provides imp…
X-ray spectra of a complete sample of extragalactic core-dominated radio sources.
Worrall, D. M.; Brunner, H.; Staubert, R. +1 more
We present ROSAT soft X-ray spectra for the members of a complete sample of 13 core-dominated, flat radio spectrum sources. The sample comprises all radio sources from a flux-limited radio catalog (S_5 GHz_ > 1 Jy; Kuehr et al.) which are north of δ= 70deg, at galactic latitudes b > 10deg, and have a flat radio spectrum between 1.4 and 5 GHz…
The extent of variability in the stellar wind of the O7.5 giant ξ Persei
Kaper, L.; Henrichs, H. F.; Nichols, J. S.
Using high-time-resolution ultraviolet spectroscopy, we present evidence that variability in the stellar wind of the O7.5 III(n)((f)) star ξ Per takes place essentially over the whole velocity range over which the wind is observable in absorption: from ~-100 km/s in the SiIV line up to -2750 km/s in NV and CIV, about 400 km/s beyond the terminal v…
Studies of early-type variable stars. XI. Absolute parameters of the Algol system RZ Cassiopeiae.
Maxted, P. F. L.; Hilditch, R. W.; Hill, G.
A new spectroscopic orbit is presented for the semi-detached eclipsing binary system RZ Cas (HD 17138, P=1.195 days, alpha(2000.0) = 2 h 48.9 m, alpha = +69 deg 38 min, (A3V+KO), based on Reticon observations with the Dominion Astrophysical Observatory (DAO) 1.2 m telescope and coude spectrograph. We find: mp sin 3 i = 2.16 +…
Boron in the extreme Population II star HD 140283 and the production of light elements in the Early Galaxy
Gilmore, G.; Gustafsson, B.; Lambert, D. L. +4 more
Using observations of the 2496.7A Bi line with the HST GHRS at a nominal resolving power of 90,000, we have found the abundance of boron of HD140283 to be logɛ_B_(=12+log(N_B_/N_H_))=0.34+/-0.20. This result is found when a significant non-LTE effect in the formation of the Bi line is taken into account. The resulting N_B_/N_Be_ ratio is about 17 …
On the neon abundance in PG 1159-type central stars on planetary nebulae.
Rauch, T.; Werner, K.
We announce the first detection and identification of a neon line in the spectra of hot central stars of planetary nebulae. It concerns the 3644A absorption line of highly ionised neon (Ne VII) in the extremely hot (T_eff_ > 100000 K) PG1159-type (i.e. hydrogen deficient) objects RXJ2117+3412, NGC246, and K 1-16. We present medium resolution sp…
On the nickel abundance in hot hydrogen-rich white dwarfs.
Werner, K.; Dreizler, S.
We present a non-LTE iron and nickel abundance analysis of four hot hydrogen rich white dwarfs from high resolution IUE spectra. The investigation aims at the determination of the Ni/Fe ratio in order to investigate if radiative acceleration prevents gravitational settling of both elements. We succeeded in the first identification of nickel lines …