Search Publications
Studies of symbiotic stars. VI. The eclipsing symbiotic nova AS 338.
Munari, U.
The nature and evolution of AS 338 is investigated. An extensive new set of photometric and spectrophotometric/UE, optical and IR data is presented, covering the period 1962-1991. It is found that AS 338 is a symbiotic nova that entered the outburst phase in late 1981. The outburst, far to be concluded, has been large in amplitude and of long dura…
Non-LTE line formation for iron group elements.
Butler, K.; Becker, S. R.
A non-LTE line formation calculation for Fe v is introduced. The data for radiative bound-bound transitions which have been derived as part of this work are described and their accuracy is evaluated. The theoretical non-LTE spectrum of Fe v is compared to the HST spectrum of the sdO star BD + 75 deg 325 resulting in a determination of the iron abu…
Stratification of chemical elements in the atmosphere of the AP star 53 Camelopardalis.
Babel, J.; Lanz, T.
A detailed abundance analysis of Cr, Fe, Mn, Ca, and Ti in the Ap star 53 Cam from IUE high-resolution spectra has been performed. It is found that UV lines give significantly lower abundance than visible lines for Cr and Fe. Theoretical spectra of Cr II line calculated with the stratified chromium abundance distributions predicted a priori by the…
R Aquarii : an attempt at a unified model.
Burgarella, D.; Vogel, M.; Paresce, F.
Consideration is given to a new model of R Aqr in which the binary system is composed of an M7 Mira with a mass of about 1.5 solar mass, a temperature of about 2800 K, a bolometric magnitude of about -4.56, and a radius of about 300 solar radii, plus a hot stellar source in an intermediate phase between a subdwarf and a white dwarf with a radiatio…
Studies of symbiotic stars. V. The dust-free yellow system He 2-467.
Munari, U.; Buson, L. M.
Results are presented of simultaneous photometric and spectroscopic observations of He2-467 in the infrared, optical, and satellite ultraviolet. It was found that the He2-467 star system consists of a G6 III star and a very hot (T of about 2 x 10 exp 5 K), luminous (L of about 5000 solar luminosities), and compact (R of about 0.06 solar radius) co…
Migrating optical depth enhancements in the UV wind lines of the WolfRayet star HD 93131.
Smith, L. J.; Prinja, R. K.
We report on the first identification of migrating opacity enhancements in the ultraviolet wind-lines of a Wolf-Rayet star. Systematic variability is identified in the He II lambda 1640 P Cygni profiles HD 93131 (WN 7), and is interpreted in terms of the formation and blueward migration of discrete absorption features. The properties of the featur…
TYCHO Data Analysis. Overview of the Adopted Reduction Software and First Results
Snijders, M. A. J.; Grewing, M.; Pedersen, H. +15 more
In the Tycho project astrometric and photometric data of about 1,000,000 stars to a limit of B = 12 mag will be derived. The brightest 500,000 stars will obtain magnitudes in two colors BT and VT, the fainter 500,000 usually only one broad-band magnitude T. There is confidence that an accuracy will be achieved about 0.03 arcsec for positions and 0…
Multiwavelength observations of RV Tauri stars. I. AC Herculis.
Evans, A.; Shenton, M.; Albinson, J. S. +6 more
We present ultraviolet, optical and infrared (including IRAS) observations of the RV Tauri star AC Her. IRAS LRS spectra suggest that the dust shell of AC Her may consist of both silicon carbide and silicates, and modeling of the optical-IR flux distribution suggests the presence of at least two distinct dust shells, the larger of which may be the…
The origin of the X-ray emission in 3C 273 and 3C 120.
Walter, R.; Courvoisier, T. J. -L.
We present an analysis of simultaneous X-ray and ultraviolet observations of the two quasars 3C 273 and 3C 120 which exhibit very similar multi-waveband spectra. This investigation is limited to the long term variations observed in the two spectral bands and to their correlations. In both objects, the X-ray and ultraviolet lightcurves are not coup…
Ultraviolet and optical spectra of central stars of halo planetary nebulae.
Pena, M.; Torres-Peimbert, S.; Ruiz, M. T.
UV and optical spectrophotometric data on central stars of eight Population II planetary nebulae are analyzed. Visual magnitudes, spectral classification, color temperatures, and luminosities are derived from these data. All the stars in the sample exhibit an absorption-type spectrum, and most of them have normal H and He photospheric abundances, …