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We present photometric observations and transit solutions of the exoplanets XO-2b, HAT-P-18b and WASP 80b. Our solution of the XO-2b transit gave system parameters whose values are close to those of the previous studies. The solutions of the new transits of HAT-P-18b and WASP 80b differ from the previous ones by bigger stellar and planet radii. We obtained new values of the target initial epochs corresponding to slightly different periods. Our investigation reaffirmed that small telescopes can be used successfully for the study of exoplanets orbiting stars brighter than 13 mag. more...

Photometric and spectral observations of the W UMa binaries FI Lyn, UV Lyn, and NSVS 781878 with periods of around 9.5–10 hr were carried out in order to determine their global parameters by simultaneous light curve and radial velocity curve solutions. We found that the three targets have shallow‐contact configurations with close in mass and radius components. UV Lyn is of W‐subtype, NSVS 781878 is of A‐subtype, while FI Lyn may be considered as binary in thermal contact. Our data show evidences of photospheric activity of the targets but not of emission in the Hα line. The surface inhomogeneity of UV Lyn is stable during the last several decades. Its O–C diagram implies presence of third body with a period of 24 years. The distances of FI Lyn, UV Lyn, and NSVS 781878 calculated from the derived luminosities coincide with those obtained by GAIA astrometrically. [ABSTRACT FROM AUTHOR] more...

In this paper, we present high- and middle-resolution spectral observations of seven heartbeat (HB), highly eccentric, Kepler binaries: four of them (KIC 3230227, KIC 03547874, KIC 03749404, KIC 07672068) are SB2 stars and the remaining three (KIC 04949194, KIC 05960989, KIC 10092506) are SB1 stars. The flux amplitudes of their HB signals are from 0.001 to 0.01. Five targets of the sample with eccentricity above 0.64 show tidally induced oscillations, which are harmonics of the orbital period. The orbital and global parameters of all targets were determined as a result of simultaneous modelling of our spectral observations and Kepler photometric data. They exhibit that the masses and radii of some target components do not obey the temperature-mass-radius relation of main-sequencestars. Although our targets do not obey precisely the theoretical period-eccentricity relation, they confirm the previous conclusion that HB stars draw the upper envelope of the eccentricity-period distribution. We did not find simple empirical dependences of the amplitude of the HB signal on the orbital and global parameters of the targets. [ABSTRACT FROM AUTHOR] more...

We carried out photometric and low-resolution spectral observations of six eclipsing ultrashortperiod binaries with main-sequence (MS)components. The light-curve solutions of the Rozhen observations show that all targets are overcontact systems. We found a well-defined empirical relation between period and semi-major axis for the short-period binaries and used it for estimation of the global parameters of the targets. Our results revealed that NSVS 925605 is quite an interesting target: (i) it is one of a few contact binaries with M components; (ii) it exhibits high activity (emission in the H® line, X-ray emission, large cool spots, non-Planck energy distribution); (iii) its components differ in temperature by 700 K. All the appearances of high magnetic activity and the huge fill-out factor (0.7) of NSVS 925605 may be a precursor of the predicted merging of close magnetic binaries. Another unusual binary is NSVS 2700153, which reveals considerable long-term variability. [ABSTRACT FROM AUTHOR] more...

CCD photometric observations in VRI colours and spectroscopic observations of the newly discovered eclipsing binary GSC 2314−0530 (NSVS 6550671) with dMe components and a very short period of d are presented. The simultaneous light-curve solution and radial velocity solution allow us to determine the global parameters of GSC 2314−0530: K; K; pc. The chromospheric activity of its components is revealed by strong emission in the Hα line (with mean Å) and several observed flares. Empirical relations for mass– , mass–radius and mass–temperature are derived on the basis of the parameters of known binaries with low-mass dM components. [ABSTRACT FROM AUTHOR] more...

Our photometric CCD observations of the short-period cataclysmic star AR UMa in 2008 during its low state revealed light variability with a bigger period (by around 10%) and considerably smaller amplitudes than the previous ones. The light curve had a single-wave shape, opposite to the previously observed low states which revealed doubled-humped shape. [ABSTRACT FROM PUBLISHER] more...

We propose a new approach for a solution of the planet transit problem that is based on numerical calculation of integrals. The paper presents our method for the case of linear limb-darkening law and orbital inclination i = 90°, and illustrates the work of the code PTS written on the basis of our approach. [ABSTRACT FROM PUBLISHER] more...