The ratios of hydrogen Balmer emission line intensities in cataclysmic variables are signatures of the physical processes that produce them. To quantify those signatures relative to classifications of cataclysmic variable types, we applied the multivariate statistical analysis methods of principal components analysis and discriminant function analysis to the spectroscopic emission data set of Williams (1983). The two analysis methods reveal two different sources of variation in the ratios of the emission lines. The source of variation seen in the principal components analysis was shown to be correlated with the binary orbital period. The source of variation seen in the discriminant function analysis was shown to be correlated with the equivalent width of the Hβ line. Comparison of the data scatterplot with scatterplots of theoretical models shows that Balmer line emission from T CrB systems is consistent with the photoionization of a surrounding nebula. Otherwise, models that we considered do not reproduce the wide range of Balmer decrements, including ‘inverted’ decrements, seen in the data.

We report the results of maximum entropy eclipse-mapping analysis of an ensemble of light curves of the dwarf nova V4140 Sagitarii (V4140 Sgr) with the objective of studying the spatial distribution of its steady-light and flickering sources in quiescence, and the changing disk structure during an outburst.

Our UBV(RI)C CCD photometry of a WZ Sge-type dwarf nova OT J213806.6+261957, discovered on May 6, 2010 at 8.4 mag, is presented. The analysis of our ~ 10000 CCD images, taken at observatories in Russia, Ukraine and Slovakia during May-November 2010, revealed the presence of ordinary and late superhumps. Fast brightness variations (flickering) on a time scale of minutes were also detected.

I present results of a search for cataclysmic variables (CVs) and chromospherically active binaries (ABs) as counterparts to X-ray sources detected with Chandra in six Galactic globular clusters (GCs): M 4, M 28, M 30, M 71, M 80, and NGC 6752. Binary systems play a critical role in the evolution of GCs, serving as an internal energy source countering the tendency of GC cores to collapse. Theoretical studies predict dozens of CVs in the cores of some GCs (e.g., 130 for M 28, 40 for M 30). A number of such binaries are also expected outside the core radius. However, few CVs are known so far in GCs. Using the 4.1m SOAR telescope, I have found 25 stars with Hα excess in the observed clusters. Six are candidate CVs, five are candidate active binaries. The other 14 objects with Hα excess are probably foreground/background stars or extragalactic sources.

We have conducted an extensive photometric search for dwarf nova (DN) outbursts in 16 Galactic globular clusters (GCs). The survey was based on the rich photometric data collected by the Cluster AgeS Experiment (CASE) team. We have identified two new DNe. Together with previously known systems this gives the total number of 12 known DNe in 7 Galactic GCs. Inserting artificial light curves of “DNe” into frames of investigated clusters allowed us to assess completeness of the search. Our results clearly show that outbursting cataclysmic variables (CVs) are very rare in GCs in comparison to field CVs where half of the systems belongs to DNe. Recent X-ray observations of GCs lead to identification of hundreds of compact binaries. Many of them are promising candidates for CVs. The theory also predicts that dozens of white/red dwarf binaries should form in the cores of GCs via dynamical processes or internal evolution of the binaries. Our results rises the question about possible causes of paucity of outbursts in GCs.

We report on the results of our 2004 monitoring program of M22, designed to search for CVs undergoing dwarf nova (DN) eruptions. We wish to compare these globular cluster systems to similar ones in the field and determine if their different formation mechanisms result in different properties. We present a light curve for a CV candidate that went into outburst during May. Data were reduced with the ISIS image subtraction routine. Our ground-based results are consistent with previous HST measurements, and confirm the DN nature of the outburst. We also report on further attempts to apply the ISIS software to look for additional outbursts of this object during 2004 as well as to identify other variable candidates in the core of M22.

We present the results of J-, H-, and K-band spectroscopy on three SU UMa-type dwarf novae with orbital periods of 1.33 – 1.37 hr. We performed the SED fitting for the obtained spectra by assuming a power-law distribution for the accretion disk and using template spectra of late-type dwarfs for secondary star. ASAS 002511+1217.2 and EQ J183926+260409 are WZ Sge-type or WX Cet-type dwarf novae. We found strong water absorption features in their spectra, which are characteristic in late M- or L-type dwarfs. The SED fitting suggests that their secondary contributions to the overall SED are less than one third. We identified the secondary stars as M9 and L1 type dwarfs, which are rather less massive but still normal stars. The spectrum of SDSS J013701−091235 is dominated by the secondary component. Spectral features of this object are similar to those of an early M-type dwarf in spite of its short orbital period. The spectrum of SDSS 0137 strongly suggests that the evolutionary path of this object is different from that of ordinary CVs, and this object is a candidate of EI Psc-like systems.

We present selected results of observations and monitoring of cataclysmic variables (CVs) and related objects by the instruments IBIS and OMC onboard INTEGRAL. We analyse the behaviour of the intermediate polar (IP) V1223 Sgr in a state which we call a shallow low state. We present far X-ray spectra ($E$ up to 60 keV), and the optical and far X-ray orbital modulation. The relation between far X-ray and optical flux appears to be stable over about 400 days. We also present far X-ray observations of some other CVs (or at least upper limits of their far X-ray fluxes) and show that the systems with magnetized white dwarf (like polars and IPs) are observable with INTEGRAL. The OMC light curves show that an outburst and a shallow low state of IX Vel are caused by the mass transfer variations, and not by the thermal instability of the disk, and that the amplitude of the flickering decreases with the decreasing intensity of the “stable” component.

The recurrence time $T_{\rm C}$ of outbursts of the remarkable and unique system, the Rapid Burster (MXB 1730–335), observed by ASM/RXTE, is analyzed by the method of the O–C residuals. The variations of $T_{\rm C}$ are large and occur all the time, but generally they are not chaotic; the mean value of $T_{\rm C}$ is 160 days between the years 1996–2005 but a large shortening of $T_{\rm C}$, accompanied by a large decrease of the maximum intensity $I_{\rm max}$ and the relative energy RE (energy output) of most outbursts, occurred in this interval. The outbursts are found to display a correlation between RE and $I_{\rm max}$, but no correlation with the outburst duration. The observed behaviour is discussed in terms of the thermal instability of the accretion disk. A comparison of this prototype with other neutron star soft X-ray transients, like Aql X-1 and 4U 1608–52, helps us find the common links in the disk behaviour in such systems.