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The ultraviolet variability of the symbiotic star HBV 475. II. Study of line flux variations.
Schmutz, W.; Nussbaumer, H.; Mueller, B. E. A.
The symbiotic star HBV 475 (= V1329 Cyg) is one of the few symbiotics where periodic variations in the ultraviolet line fluxes have been observed. The authors collect the IUE observations between June 1979 and December 1984. Extending the work of Nussbaumer and Schmutz (1983), who presented a detailed study of this object, the authors establish th…
The ultraviolet spectrum of upsilon Sagittarii.
Hack, M.; Parthasarathy, M.; Cornachin, M.
IUE high resolution spectra of Upsilon Sgr are analyzed. The interstellar lines of metal and ionized elements and the phase-dependent variations of the stellar and circumstellar lines are studied. The characteristics (absorption strength and terminal velocities) of stellar wind features at all the orbital phases are described. The data reveal that…
Multilevel line formation in the expanding envelope of zeta Aur/VV CEP systems.
Baade, R.
The Sobolev method is the basis of the present multilevel formalism for UV line profiles in Zeta Aur systems; atomic models for Si II and Fe II UV multiplet 9 and 191 are used to study problems implicated in the two-level approximation. The first Si II model encompasses 11 composite levels together with two continua, and all possible interlocking …
Circumstellar envelope around the binary system lambda And.
Glebocki, R.; Sikorski, J.; Bielicz, E. +1 more
Asymmetries in emission peaks and relative shifts of h3 and k3 absorptions in Mg II resonant lines are analysed in 31 spectra of λ And (long period RS CVn type star) obtained in the years 1978 - 1983. An evident correlation is found between these values and the orbital phase. The only reasonable explanation of this correlation is the existence of …
Autoionizing levels in Si II and identification of the 1400 Å feature of Ap-Si stars.
Artu, M. -C.
The author reports four new high energy levels of Si II belonging to the core-excited terms 3s3p(1P)3d2D0 and 2P0. They are determined from the classification of six laboratory UV emission lines. A broadening due to autoionization is detected for two of them. These results fix the energy of th…
Wide-band X-ray observations of MK 501.
Ubertini, P.; Bazzano, A.; Brunner, H. +3 more
The BL Lacertae object MK 501 was observed by EXOSAT on 25 July 1984 for 3.65 hours. The data from the low energy (LE) and medium energy (ME) instruments suggest a single power law spectrum over the energy range 0.04 - 8 keV with a photon index of 2.5±0.1, an intensity at 1 keV of 0.022±0.003 photons/cm2s keV and a column density consis…
A soft X-ray observation of ω Centauri with EXOSAT.
van Paradijs, J.; Jansen, F.; Verbunt, F. +2 more
In an observation with the LE1 CMA detector of the EXOSAT observatory the authors have detected two of the X-ray sources previously discovered in the globular cluster ω Cen with the IPC detector on board of the Einstein satellite. They give improved positions for these two sources. On the basis of comparison of the EXOSAT and Einstein count rates …
HD 32918 : Ultraviolet spectrum and optical behaviour.
Grewing, M.; Bianchi, L.; Cassatella, A.
The first ultraviolet observations of HD 32918, a southern member of the FK Comae class, are presented. The observations were taken with the IUE satellite at two phases of the optical light curve, with simultaneous photometric coverage over more than one cycle in order to monitor the activity state of the star. The star shows very strong UV emissi…
The symbiotic star BX Monocerotis.
Altamore, A.; Rossi, C.; Friedjung, M. +4 more
The nature of BX Mon, a peculiar star characterized by a composite spectrum and very long period photometric variability, has been investigated. The star has been included in an extensive program of ESO observations of emission line stars. New results are discussed based on coordinated optical (IDS) and infrared observations made in February 1983,…
The MG II emission in a sample of regular-period RS CVn systems.
Fernandez-Figueroa, M. J.; de Castro, E.; Sedano, J. L.
The authors have studied a sample of ten RS CVn systems by means of IUE high resolution long wavelength spectra. A general trend toward decreasing chromospheric activity (Rhk) for slower rotating stars has been found. Considering the Rhk values and their relation with structural parameters (Teff, log g, log Pr…