We found cyclical variations in the quiescent magnitudes and outburst intervals of 21 dwarf novae, 1 nova and 1 nova-like star produced by the solar-type cycles of the late-type secondary components. More than 70% of individual systems in this work are first studied by Fourier periodogram analysis. It seems that the mean cycle amplitudes of the quiescent magnitudes are considerably larger for SU UMa stars. Cyclical modulations of quiescent magnitudes found for the stars, which have orbital periods below the period gap, support the hypothesis that even almost fully convective secondaries may possess activity cycles. The estimated probability density functions show peaks at 9.7, 7.9 and 8.6 yrs for cataclysmic variables (CVs), single main-sequence stars (MS) and all stars (CVs+MS), respectively. Using a larger set of data, we confirm that there is no correlation of the cycle period with the rotational regime of the secondary star. It is also confirmed that cycle periods of CVs are in the range of those of single main-sequence stars. We note that the observational cycle parameters (i.e. cycle period, Pcyc, and cycle amplitude of quiescent magnitudes, ∆m) do not seem in relation with any other parameter such as masses of primary and secondary stars, mean outburst interval, mean outburst duration, mean decline and rise rate of outbursts, absolute magnitudes in quiescent and outburst states etc.

Abstract. The long-term visual light curve parameters of 36 dwarf novae are measured. The data is anayzed in search of likely relationships among the light curve parameters and system parameters. New relations of the orbital period with the mean light curve parameters are given. Our findings for the correlation analysis of individual systems agree with some of the results in previous studies. Almost all of the systems in this study have a bimodal frequency distribution of the outburst duration. By comparing the observational correlations with their theoretical counterparts, we find that the value of the viscosity parameter of the disk instability model is α hot ≈ 0.2.

In this paper, we report the discovery of a high‐energy component of the X‐ray spectra of U Gem, which can be observed while the source is in outburst. We used Chandra and XMM–Newton observations to compare the quiescence and outburst X‐ray spectra of the source. The additional component may be the result of the reflection of X‐rays emitted from an optically thin plasma close to the white dwarf, from the optically thick boundary layer during the outburst. Another possible explanation is that some magnetically channelled accretion may occur on to the equatorial belt of the primary causing shocks similar to the ones in the intermediate polars as it was suggested by Warner and Woudt. We have also found a timing structure at about 73 mHz (∼13.7 s) in the RXTE observation, resembling dwarf novae oscillations.

In this paper the results of matching the RAdial Velocity Experiment (RAVE), a spectroscopic Southern hemisphere survey (9 < I DEN IS < 12), and XMM-Newton Serendipitous Source Catalogue (3XMM) are presented. The latest data releases of RAVE and XMM were matched and a X-ray RAVE catalogue of 1071 stars was obtained. Then the catalogue was checked for possible Gould Belt (GB) members. We obtained a subsample of 10 stars that meet the GB membership criteria. This subsample and GB member candidates were tested photometrically and kinematically. Among the members there are two BY Dra type variables, an NGC2451 open cluster member, a high proper motion star. The rest are regular main sequence stars. The members have very low velocity dispersions which lead us to think that the members belong in a single structure. We also found out that a kinematical GB membership test might be possible to derive given a large enough GB member sample as they fit in a narrow interval in space velocity diagrams.