Related papers: HD 26172: an active solar-type subgiant in a close…
We present the first orbital elements for the massive close binary, HD 101131, one of the brightest objects in the young, open cluster, IC 2944. This system is a double-lined spectroscopic binary in an elliptical orbit with a period of…
We report the discovery of a new BY Dra-type binary identified as the optical counterpart of the bright source RX J0222.4+4729 detected during the ROSAT All-Sky Survey (Voges et al. 1996). The star is a $V \sim 11.1$, near-by ($\sim 30$…
Taking into account a range of parameters determined from the evolutionary models and available observational data, the detailed non-LTE spectra for the primary star and the irradiated donor star in the only known eclipsing AM CVn system to…
We report the discovery of a new detached, double white dwarf system with an orbital period of 39.8 min. We targeted SDSS J163030.58+423305.8 (hereafter J1630) as part of our radial velocity program to search for companions around low-mass…
The archival spectrum of SDSSJ212531.92-010745.9 shows not only the typical signature of a PG1159 star, but also indicates the presence of a companion. Our aim was the proof of the binary nature ofthis object and the determination of its…
The young binary system HD 350731 is a noteworthy laboratory for studying early-type binaries with similar components. We present here the analysis of differential multi-color photometric and spectroscopic observations for the double-lined…
Photometric observations in V and I bands and low-dispersion spectra of ten ultrashort-period binaries (NSVS 2175434, NSVS 2607629, NSVS 5038135, NSVS 8040227, NSVS 9747584, NSVS 4876238, ASAS 071829-0336.7, SWASP 074658.62+224448.5, NSVS…
We report the discovery of a low-mass totally eclipsing system in the young (age$\simeq$28 Myr) open cluster NGC2232, during a scrutiny of their TESS light curves. The follow-up study of this detached system, TIC 43152097, is based on…
We announce the discovery of a new eclipsing hot subdwarf B + M dwarf binary, EC 10246-2707, and present multi-colour photometric and spectroscopic observations of this system. Similar to other HW Vir-type binaries, the light curve shows…
We present BVR observations of DK CVn from 2007 and 2008. We analysed the BVR light curves of the system and obtained the system's parameters. Using the `q-search' method, we measured the mass ratio of the system (q) as 0.55. Taking the…
Measuring surface differential rotation (DR) on different types of stars is important when characterizing the underlying stellar dynamo. It has been suggested that anti-solar DR laws can occur when strong meridional flows exist. We aim to…
We present the results of a study of the star HD 34736. The spectropolarimetric observations carried out at the 6-m telescope showed the presence of a strong variable longitudinal magnetic field, exceeding -4500 G. The analysis of the…
I review detached binaries consisting of white dwarfs with either other white dwarfs or low mass main-sequence stars in tight orbits around them. Orbital periods have been measured for 15 white dwarf/white dwarf systems and 22 white dwarf/M…
We present observations proving the close binary nature of the central stars belonging to the planetary nebulae (PNe) NGC 6326 and NGC 6778. Photometric monitoring reveals irradiated lightcurves with orbital periods of 0.372 and 0.1534…
Methods to measure masses of PG1159 stars in order to test evolutionary scenarios are currently based on spectroscopic masses or asteroseismological mass determinations. SDSSJ212531.92-010745.9, a recently discovered PG1159 star in a close…
We present high-speed, three-colour photometry of the eclipsing cataclysmic variable SDSS J150722.30+523039.8 (hereafter SDSS J1507). This system has an orbital period of 66.61 minutes, placing it below the observed ``period minimum'' for…
The {\it TESS} periodograms of the SALT survey catalogue of hydrogen-deficient stars were searched for evidence of short-period variability. Periodic light curve variations were identified in 16 stars out of 153 catalogue objects, of which…
Due to the recent increase in the availability of photometric time-series databases, the characterisation of low-mass eclipsing binaries for the study of their orbital and physical parameters is now possible in large samples and with good…
In 2007, the young star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a complex series of deep eclipses over 56 days. This was attributed to the transit of a ring system filling a large fraction of the Hill sphere of an unseen substellar…
We confirmed the binary nature of the Be star 7~Vul, derived a~more accurate spectroscopic orbit with an orbital period of (69.4212+/-0.0034) d, and improved the knowledge of the basic physical elements of the system. Analyzing available…