We report the study of the accretion disk structure of the period bouncer cataclysmic variable EZ Lyn (SDSS J080434.20+510349.2) in quiescence based on our new time-resolved photometric and spectroscopic observations and data extracted from archives. The object magnitude now is V = 17.95(5), close to its brightest before the first superoutburst in 2006. We confirmed the presence of the small eclipse in the optical light curve. The spectra obtained in quiescence at different epochs look similar. However, the contribution of the disk and intensities of emission lines are strongly varied. We singled out pure accretion disk spectra and found that the Balmer decrement Hα:Hβ:Hγ:Hδ = 1.61:1.0:0.76:0.59 is comparable with one at bright accretion disks in longer period cataclysmic variables. The decrement suggests that emission lines are excited collisionally in an optical thin part of the disk with average density and temperature of logN ₀ = 12.5(2) and T = (10–15) × 10³ K. Based on the photometric data and our modeling techniques, we redetermined the mass of M _WD = 0.85(1) M _⊙ and the current effective temperature T _WD,eff = 11,250(50) K of the white dwarf. The secondary has mass of M ₂ = 0.042(14) M _⊙. The system inclination is 79.0°(2). The mass accretion rate is about M ̇ ≈ ( 0.3 – 3.0 ) × 10 − 12 M ⊙ yr⁻¹. The disk luminosity, together with results from light-curve modeling, suggests a low effective temperature ∼2500 K of the continuum emitting region, where also the spiral arm pattern is hosted.

There is growing evidence that many Be stars are parts of binary systems. As the B-type primaries are very fast rotators and their spectral lines may be distorted by the circumstellar material, it is not easy to measure their radial velocity directly from the spectral lines. It has been shown that some Be binaries exhibit peak intensity variations consisting of double-peaked H$\alpha$ lines that are phase-locked with orbital periods. We searched for such variations in the spectra of 12 Be stars, including several known and suspected binaries. Our results include confirmation of the orbital periods in $\nu$ Geminorum, $ϵ$ Capricorni, $\kappa$ Draconis, 60 Cygni, and V2119 Cygni, its refinement in o Puppis, as well as suggesting hints for binarity in o Aquarii, BK Camelopardalis, and 10 Cassiopeae. Monitoring of the H$\alpha$ line profile variations in $\beta$ Canis Minoris for over the last 10 years gives further support to the existence of a 182.5-day period found earlier in a smaller set of data. A similar but still preliminary period (179.6 days) was found in the H$\alpha$ line profile variations in $\psi$ Persei. It is shown for the first time that $\nu$ Geminorum exhibits phase-locked variations in the H$\alpha$ emission peak intensity ratio and, therefore, is a part of the inner binary in this triple system. Our results show that the mentioned phase-locked peak intensity variations are observed in more Be binary systems than previously known and can be used to search for binarity of Be stars when application of other methods is inconclusive.

We present a new study of the Z Cam-type eclipsing cataclysmic variable AY Piscium with the aim of determining the fundamental parameters of the system and the structure of the accretion flow therein. We use time-resolved photometric observations supplemented by spectroscopy in the standstill, to which we applied our light-curve modeling techniques and the Doppler tomography method, to update system parameters. We found that the system has a massive white dwarf M _WD = 0.90(4) M _☉, a mass ratio q = 0.50(3), and the effective temperature of a secondary T ₂ = 4100(50) K. The system inclination is i = 74.°8(7). The orbital period of the system P _orb = 0.217320523(8) day is continuously increasing at a rate of P ̇ orb = + 7.6 ( 5 ) × 10 − 9 day yr⁻¹. The mass-transfer rate varies between 2.4 × 10⁻¹⁰ M _⊙ yr⁻¹ in quiescence up to 1.36 × 10⁻⁸ M _⊙ yr⁻¹ in outburst. The accretion disk transitions from the cooler, flared, steady-state disk to a warmer state with a practically constant and relatively high disk height. The mass-transfer rate is about 1.6 × 10⁻⁹ M _⊙ yr⁻¹ in the standstill. The Balmer emission lines show a multicomponent structure similar to that observed in long-orbital-period nova-like systems. Out of standstill, the system exhibits outburst bimodality, with long outbursts being more prominent. We conclude that the Balmer emission lines in AY Psc are formed by the combination of radiation from the irradiated surface of the secondary, from the outflow zone, and from winds originating in the bright spot and the disk’s inner part.

$\kappa$ Draconis is a binary system with a classical Be star as the primary component. Its emission-line spectrum consists of hydrogen lines, notably the H$\alpha$ line with peak intensity ratio (V/R) variations phase-locked with the orbital period P = 61.55 days. Among binaries demonstrating the Be phenomenon, $\kappa$ Dra stands out as one of a few systems with a discernible mass of its secondary component. Based on more than 200 spectra obtained in 2014–2023, we verified the physical parameters and constructed the mass function. We used part of these data obtained in 2014–2021 to investigate regions in the circumstellar disk of the primary component that emit the H$\alpha$ line using the Doppler tomography method. The results show that the disk has a non-uniform density distribution with a prominent enhancement at ${\mathrm{V}}_y$ ≈ 99 km ${\mathrm{s}}^{-1}$ and ${\mathrm{V}}_x$$\approx -6$ km ${\mathrm{s}}^{-1}$ that corresponds to a cloud-like source of the double-peaked H$\alpha$ line profile. We argue that this enhancement’s motion is responsible for the periodic variations in the H$\alpha$ V/R ratio, which is synchronised in orbital phase with the radial velocity (RV) of absorption lines from the atmosphere of the primary component.

κ Draconis is a binary system with a classical Be star as the primary component. Its emission-line spectrum consists of hydrogen lines, notably the Hα line with a peak intensity ratio (V/R) variations phase-locked with the orbital period P = 61.55 days. Among binaries demonstrating the Be phenomenon, κ Dra stands out as one of a few systems with a discernible mass of its secondary component. Based on more than 200 spectra obtained in 2014 − 2023, we verified the physical parameters and constructed the mass function. We used part of these data obtained in 2014 − 2021 to investigate regions in the circumstellar disk of the primary component that emit the Hα line using the Doppler tomography method. The results show that the disk has a non-uniform density distribution with a prominent enhancement at Vy≈ 99 km s−1 and Vx≈−6 km s−1 that corresponds to a cloud-like source of the double-peaked Hα line profile. We argue that this enhancement’s motion is responsible for the periodic variations of the Hα V/R ratio, which is synchronised in orbital phase with the radial velocity (RV) of absorption lines from the atmosphere of the primary component.