ALBERT

Notes: Abstract Initial results are presented from a study of H γ profiles in the two interacting binaries KX And and RX Cas of W Serpentis type. The used CCD spectra with a resolution of 0.13Å/px were obtained with the 2.2m telescope and the Coudé spectrograph at the German-Spanish Astronomical Center at Calar Alto/Spain. KX And. This star is probably a non-eclipsing member of the W Serpentis type interactive binaries and has a period of P = 38.908 days. Our seven spectra of KX And were obtained at phase 0.54 – 0.75. The P Cyg profiles of the H γ line during our observations indicate an expanding shell. The asymetry becomes blue-sided at phase 0.67 and increases thereafter. This points toward a strong outflow of matter in the vicinity of the L3 point. RX Cas. According to the model of Andersen et al. (1988) the primary is a mid-B type star with M = 5.8M ⊙ and R = 2.5R ⊙. The star is completely obscured by a geometrically and optically thick disk, which is supplied by mass transfer from the other component. The secondary is a K1 giant with M = 1.8M ⊙ and R = 23.5R ⊙ and fills out his critical Roche lobe. Radiative and geometrical properties of the disk are variable and its structure is probably not homogenous. Five spectra of RX Cas were obtained during the primary eclipse (phase 0.95 – 0.19). The observed double-peak emission is seen only after the eclipse with a separation of ≈ 250 km/s peak-to-peak, while during the eclipse an asymetric line profile can be observed with a red-shifted emission always presented. Also, a central emission at φ = 0.94 should be noticed, probably originating in the vicinity of L1. The observations of both systems indicate that we are dealing with strongly interacting binaries. Further observations are planned for better covering of phase.

Notes: Abstract The interacting binary V367 Cyg is contained in the original list of W Serpentis stars discovered by Plavec and Koch (1978) in their initial UV study and has been subject of numerous studies, both photometric and spectroscopic. A reasonable model of the system shows the primary as a supergiant of type A7 with T eff = 8000 °K, R = 50 R ⊙ and log g = 1.5, the secondary as A0III with T eff = 10000 °K and R = 7 R ⊙. A cooler disk with a radius of ≈ 25 R ⊙ encircles the secondary and the whole system is surrounded by a gasous shell of ≈ 500 R ⊙. But there is still a considerable confusion regarding the very basic geometric and radiative properties of V367 Cyg. Therefore we have analysed the available photometric data in the framework of the semi-detached configuration which incorporates the influence of an optically thick disk around the mass gaining component. The input data have been selected from the most recent spectroscopic studies based on the optical and UV spectra. Our trial calculations show that a solution is possible in the framework of the assumed model. In our solution the disk around the gainer is in contact with the mass-loosing component and the radiative properties mimic a stellar atmosphere. This explains previous light curve solutions in terms of a contact configuration. Also, our model corrobates with a description of the W Serpentis stars as strongly interacting binaries in or near the phase of rapid mass transfer. In August 1988 we could record eight CCD spectra of the γ region with a resolution of 0.13Å/px taken during the primary eclipse (phase 0.692 – 0.163). The spectra have been obtained at the German-Spanish Observatory at Calar Alto/Spain with the 2.2m telescope and the Coudé spectrograph. The Hγ profiles display a very complex structure with at least four emission components. In the primary minimum the main emission components are of nearly the same intensity. It means, that we observe the outermost parts of the disk even during the eclipse. This is in agreement with the light curve solution. The central depth of the shell lines changes only slightly, because they belong to the circumbinary shell. Besides this, some of the shell lines show broad red- or blue-shifted wings (depending on the orbital phase). They are probably originated from the spectrum of the primary.

Notes: Abstract The X-ray heating light curve of the binary X-ray source 4U2129+47/V1727 Cgy is synthesized. A reliable solution is obtained only after accounting for the influence of an accretion disk. Model parameters achieved by the best fit are discussed. The solution is also discussed in the context of an extended OFF state.

Notes: Abstract A multifrequency analysis of the short-term photometric variations of the Be and shell star EW Lac is performed. Two data sets, almost thirty years apart, revealed similar frequency structures but significantly differ in amplitudes. The causes of variability is checked under various assumptions including spot(s) on the surface, an inhomogeneous or asymmetric envelope, tidal distortions, and the presence of a companion. The most plausible interpretation is, however, found in terms of nonradial pulsations. In particular, the problem of abrupt light changes is pointed out, an effect which is fully explained by multiperiodicity.

Notes: Abstract A frequency-analysis of the broadbandUBV photometric observations of the interacting binary star KX And has been performed in order to disclose claimed rapid periodic variations. Our analysis confirms existence of rapid variability, but disagrees with the period. In discussion we rejected rotations as possible cause of the rapid photometric variations, and found that some kind of pulsations offer plasusible explanation.

Notes: Abstract The combined 1983 campaign and Seoul data on the variable Be star EW Lac is reanalyzed. CLEANing of the Fourier transform of the present time series clearly shows more than a single period. A multiperiodic fit can account also for a sudden brightness change through frequency beating. Comparison with previous multiperiodic solutions based on data obtained in different seasons shows highly variable amplitudes of the pulsational frequencies. The consequence of this finding to variable shell activity of EW Lac is briefly pointed out.