Aims. The work is aimed at studying the circumstellar disk of the bright classical binary Be star π Aqr. Methods. We analysed variations of a double-peaked profile of the H α emission line in the spectrum of π Aqr that was observed in many phases during ∼40 orbital cycles in 2004−2013. We applied the discrete Fourier transform (DFT) method to search for periodicity in the peak intensity ratio (V/R). Doppler tomography was used to study the structure of the disk around the primary. Results. The dominant frequency in the power spectrum of the H α V/R ratio is 0.011873 day −1 , which corresponds to a period of 84.2(2) days and agrees with the earlier determined orbital period of the system, P orb = 84.1 days. The V/R shows a sinusoidal variation that is phase-locked with the orbital period. Doppler maps of all our spectra show a non-uniform structure of the disk around the primary: a ring with the inner and outer radii at V in ≈ 450 km s −1 and V out ≈ 200 km s −1 , respectively, along with an extended stable region (spot) at V x ≈ 225 km s −1 and V y ≈ 100 km s −1 . The disk radius of ≈65 R = 0.33 AU was estimated by assuming Keplerian motion of a particle on a circular orbit at the disk's outer edge.

We report the results of a long-term spectroscopic monitoring of the FS CMa type object MWC 728. We found that it is a binary system with a B5 Ve (T eff = 14000±1000 K) primary and a G8 III type (T eff ∼ 5000 K) secondary. Absorption line positions of the secondary vary with a semi-amplitude of ∼20 km s −1 and a period of 27.5 days. The system's mass function is 2.3×10 −2 M ⊙ , and its orbital plane is ∼13-15 • tilted from the plane of the sky. The primary's v sin i ∼110 km s −1 combined with this tilt implies that it rotates at a nearly breakup velocity. We detected strong variations of the Balmer and He i emission-line profiles on timescales from days to years. This points to a variable stellar wind of the primary in addition to the presence of a circum-primary gaseous disk. The strength of the absorption-line spectrum along with the optical and near-IR continuum suggest that the primary contributes ∼60% of the V -band flux, the disk contributes ∼30%, and the secondary ∼10%. The system parameters, along with the interstellar extinction, suggest a distance of ∼1 kpc, that the secondary does not fill its Roche lobe, and that the companions' mass ratio is q ∼0.5. Overall, the observed spectral variability and the presence of a strong IR-excess are in agreement with a model of a close binary system that has undergone a non-conservative mass-transfer.

Context. A growing number of Be and Oe stars, named the γ Cas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compact companion or magnetic interaction between the star and its decretion disk. Aims. To test these scenarios, we carried out a detailed optical monitoring of HD 45314, the hottest member of the class of γ Cas stars, along with dedicated X-ray observations on specific dates. Methods. High-resolution optical spectra were taken to monitor the emission lines formed in the disk, while X-ray spectroscopy was obtained at epochs when the optical spectrum of the Oe star was displaying peculiar properties. Results. Over the last four years, HD 45314 has entered a phase of spectacular variations. The optical emission lines have undergone important morphology and intensity changes including transitions between single-and multiple-peaked emission lines as well as shell events, and phases of (partial) disk dissipation. Photometric variations are found to be anti-correlated with the equivalent width of the Hα emission. Whilst the star preserved its hard and bright X-ray emission during the shell phase, the X-ray spectrum during the phase of (partial) disk dissipation was significantly softer and weaker. Conclusions. The observed behaviour of HD 45314 suggests a direct association between the level of X-ray emission and the amount of material simultaneously present in the Oe disk as expected in the magnetic star-disk interaction scenario.

Context. B[e] stars are anomalous objects around which extended circumstellar matter is present. The observed properties of the central star are significantly affected by the surrounding material. Therefore, the use of standard synthetic spectra is disputable in this case and our capability to study these objects is limited. One of the possibilities is to analyse variations of the spectral features. Long-term spectroscopic observations are required for this, but are not found in the literature. For our study we choose the B[e] star HD 50138 of the FS CMa type because of the indication that this star is a post-main-sequence star, although still not highly evolved. Therefore, it can be a good object for testing evolutionary models. Currently, HD 50138 is the most extensively observed FS CMa star which makes it an ideal object for modelling. Our observations fill the gap in the available data. Aims. To describe the variability of HD 50138 we have monitored this star spectroscopically over the last twenty years. To search for the periodicity on short-term scales, series of night-to-night observations were also obtained. We were able to obtain 130 spectra from four different telescopes -1. periods of 3000 ± 500 and 5000 ± 1000 days were detected there. We were able to catch moving humps in the Hα line, which reveal the rotating media around the star. An analysis of the correlation of equivalent widths, radial velocities, relative fluxes, and V/R ratios for various lines is presented in detail. Conclusions. We describe the spectral variability of HD 50138 over the last twenty years. Based on these data, we determine new restrictions for future modelling. We confirm the quasi-periodic behaviour of the object's spectral variability, which probably reflects mass transfer in a binary system. This behaviour also supports a recently introduced explanation of the nature of FS CMa stars as post-merger systems.

We present the results of a survey for variable stars in the core of the globular cluster M3. Our findings include the discovery of eleven new or suspected variables, including a possible W Vir, and the first period determinations for thirteen previously known variables.Comment: 9 pages, 3 figures, accepted by MNRAS, uses mn2