Dragomir Valchev Marchev

Physical parameters of components in close binary systems. I

The paper presents combined spectroscopic and photometric orbital solutions for four close binary systems: SW Lyn, QW Gem, AP Leo and V2150 Cyg. The photometric data are new, while the spectroscopy has been recently obtained within the radial velocity programme at the David Dunlap Observatory. This paper is the first in the planned series of investigations. We give an extensive description of the motivation for the series and of the main assumptions made in our solutions. The four targets of this investigation span a range of typical configurations and thus present different levels of difficulty for the combined spectroscopic and photometric orbital solutions.

Spectroscopic and Photometric Observations of the Short-Period RS CVn-Type Star UV Piscium

High-resolution spectroscopic observations around the Hα line and BVRI photometry from 1993 to 2003 of the eclipsing short-period RS CVn star BH Vir are presented. The simultaneous solution of our radial velocity curves and light curves yielded the following values for global parameters of the components: M1 = 1.173 ± 0.006 M� ; M2 = 1.046 ± 0.005 M� ; R1 = 1.22 ± 0.05 R� ; R2 = 1.11 ± 0.04 R� ;i = 87.5 ◦ ± 0.8 ◦ . The measured rotational broadening of the spectral lines corresponds to equatorial velocities V1 = 79.8 km s −1 and V2 = 68.4 km s −1 . Our data reveal considerable Hα emission excess of the two stellar components. We modelled the photometric data to find the size and location of the starspots for each year. The established decreasing trend of the spot latitudes may indicate a latitudinal cycle of at least a decade.

HIGH-SPEED BVRI PHOTOMETRY OF SS CYG AT QUIESCENCE AND AT OUTBURST

BVRI photometry of SS Cyg from the end of 1996 and the beginning of 1997 is presented. The star underwent an eruption around December 11. The amplitude of which was slightly bigger than those of observed earlier eruptions. We saw some indication of the future outburst in the decreasing of brightness in all colours by about 0.4 mag during the last two weeks before the event. The emission of the system moved strongly to the shorter wavelengths at outburst. Our multicolour data confirm the existence of a light variability with the orbital (spectroscopic) period at quiescence. Moreover we found for the first time that this variability exists also at outburst but its amplitude is 3–5 times smaller. Whereas the amplitudes of the orbital variability at quiescence decrease to the longer wavelengths, they increase at outburst to the longer wavelengths. The orbital folded curve at quiescence has two-wave shape and was fitted well by the different visibility of two diametrical opposite hot spots (210000 K) with angular size 100 on the magnetic poles of the white dwarf. An analogy between the two basic states of the U Gem-star SS Cyg, the polar AM Her and Z Cam-star RX And was found.

B and R photometry of AM her during 1993

The results from the simultaneous observations in B and R colours of AM Her are presented. Analysis of these data shows the following: (a) There are always two clear minima in the R light curves, while the secondary minimum in B light curves sometimes is not well defined; (b) The times of the minima in R and B colour nearly coincide; (c) The photometric period changes remarkably from cycle to cycle but its mean value remains constant; (d) Short stillstands on the increasing branches of the two minima are seen similar to those visible in UX UMa-type cataclysmic stars; (e) Besides the irregular flickering with time scale of a few minutes, a variability with a period 20.28 min in the two colours is established.

THE B AND Be STATES OF THE STAR EM CEPHEUS

We present eleven years of high-resolution, spectroscopic observations for the star EM~Cep. EM~Cep switches between B and Be star states, as revealed by the level of H

Multicolour Photometry of RX and During 1994/95

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Spectroscopic and photometric observations of the short-period RS CVn-type star BH Virginis

emission, but spends most of its time in the B~star state. EM~Cep has been considered to be an eclipsing, near contact binary of nearly equal-massed B stars in order to reproduce regular photometric variations; however, this model is problematic due to the lack of any observed Doppler shift in the spectrum. Our observations confirm that there are no apparent Doppler shifts in the wide spectral lines H

Physical Parameters of Components in Close Binary Systems: III

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Photometric and Hα Observations of the Cataclysmic Star UX UMa

and HeI~6678 in either the B or Be star states.The profiles of HeI~6678 typically exhibited a filled-in absorption core, but we detected weak emission in this line during the highest Be state. Given the lack of observed Doppler shifts, we model EM~Cep as an isolated Be star with a variable circumstellar disk. We can reproduce the observed H

Spectroscopic solution of the star QX Cas

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