We present all available UBV photometry of the symbiotic binary EG And obtained during the last 10 years. The light curves display a double wave through one orbital cycle. It is shown that this behaviour cannot be explained by eclipses of the two detached sources of the continuum radiation. The present models of EG And are not able to simulate satisfactorily variation in both the far ultraviolet and the optical continuum.
The rapidly rotating active stars FK Com and HD 199178 are investigated using extensive long-term photometry. The data set includes previously unpublished photometry, obtained at the Rozhen National Astronomical Observatory. We look for periodicities in the long-term photometric behaviour of both stars, as well as for spots, using light curve modelling. Special attention is paid to the behaviour of the "flip-flop" phenomenon.
Photometric observations of LQ Hya (HD 82558) obtained in 1995-2001 with the Phoenix 10 robotic telescope (Arizona) in the UBV bands with HD 82447 as the comparison star.
We present results of an extensive photometric monitoring campaign of the peculiar emission star MWC 560 that covers the range 1990-1995. The time interval corresponds to the length of the proposed orbital period of this highly peculiar binary, which attracted considerable interest in January-April 1990, when absorption components, shifted by -6000km/s from corresponding emission lines, were observed. Here we present photometric data secured during: 113 nights of conventional UBV photoelectric photometry, 45 nights of high speed UBV photoelectric photometry to study the flickering activity, and 682 visual photometric estimates. MWC 560 has experienced a decrease in magnitude since the bright (V=9.2mag) phase in 1990. After the minimum reached in May 1994 (V=10.7mag), the star is currently increasing slowly in brightness. The decrease has been accompanied in all bands by large fluctuations superimposed on the mean trend. The B-V colour has shown a steady increase by 0.0.33mag/yr. U-B has remained stable at -0.07mag since late 1990. In all the observing nights devoted to high speed photometry we observed flickering activity in MWC 560. The data show that the flickering amplitude {DELTA}U increases with the decrease of the U magnitude. Quasi-periodic variations have always been detected. A period of ~70min has been observed in ~13 nights which is close to the ~60min quasi-period reported by Michalitsianos et al. (1993). However, no coherent variability is traceable throughout the whole set of flickering data.
An analysis of photometric observations of the Be star OT Gem (HD 58050, HR 2817, 2000 position: 07 24 27.64 +15 31 02.0) is presented. A positive correlation between the light and colour variations and the emission strength was found.
A detailed analysis of a very rich collection of spectroscopic and photometric observations of the bright Be star {phi} Per (HR 496, or HD 10516, 2000 position: 01 43 39.4 +50 41 20) is presented. Earlier reports that {phi} Per is a double-lined spectroscopic binary consisting of two emission-line objects are confirmed.
Photoelectric, CCD, and photographic photometry is presented for a sample of 163 stars in the field of the short-period Cepheid SU Cyg for the purpose of searching for a putative cluster that might be associated with the Cepheid. Although the variable is situated in a clump of stars that has the appearance of a sparse cluster, the photometric evidence indicates that they are not a physical group. About two dozen B and A-type stars randomly distributed in the field lie at a common distance of 1086+/-60pc (V_0_-M_V_= 10.18+/-0.12 for R=2.94+/-0.38), but they are likely to represent at best a segment of the Vul OB4 association, which overlaps the region. SU Cyg is unlikely to be a member of that group. The close optical companion to SU Cyg, an A2 V star with a radial velocity (<VR>=-23.6+/-7.1km/s) close to the systemic velocity of the Cepheid, is a spectroscopic binary that might be physically related to the variable. Its primary importance is for helping to establish a space reddening of E_(B-V_)=0.15+/-0.01 for SU Cyg. Despite the lack of related cluster stars to SU Cyg, its two unresolved companions can be used to place restrictions on the likely luminosity of the Cepheid. The resulting value of <M_V_><=-3.02+/-0.23 relative to its companions agrees closely with a value of <MV>(PLC)=-3.03+/-0.07 obtained from the Cepheid PLC relation.
