Search

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.

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.

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.

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.