We present the results of speckle interferometric observations of 156 stars possessing global magnetic fields, carried out with the 6-m BTA telescope of the Special Astrophysical Observatory. Virtually all stars were observed between 2010 and 2012. Thirty-four stars were resolved into individual components (31 double and 3 triple), of which 14 binary systems (BD+41° 43, HD2887, HD30466, HD36540, HD36955, HD37479, HD61045, HD89069, HD 144334, HD 164258, HD349321, HD343872, HD 184471, HD 196691) and 2 triple systems (HD37140, HD338226) were for the first time resolved by the astrometric method.

We present the measurements of positional parameters of 194 nearby binary stars performed at the 6-m BTA telescope of the SAO RAS from 2002 through 2006 applying the speckle interferometric technique. The observations were conducted at central filter wavelengths ranging from 545 to 800 nm using a speckle interferometer equipped with a fast CCD and a three-stage image intensifier. A significant part of the observed systems (80 stars) are pairs, the duality of which was discovered or suspected from the Hipparcos satellite observations. The remaining stars are visual binaries and interferometric binary systems with orbital motion period estimates from several to tens of years, as well as the pairs with slow relative motion of the components, used for gaging the image scales and positional angle calibrations.

We continue the presentation of new orbits for Hipparcos binaries determined from regular speckle interferometric observations. Most of the data were collected in the period between 1998.77 and 2004.82 using the 6 m BTA telescope of the Special Astrophysical Observatory in Zelenchuk. New orbits are presented for six pairs: HIP 4809, HIP 4849, HIP 5531, HIP 19206, HIP 105947, and HIP 114922. One of the pairs, HIP 114922, has M dwarf components orbiting with a period of 19.72 yr. Two binaries, HIP 4809 and HIP 5531, have luminosity class IV components. The periods of the orbits range from 7.30 yr to 28.99 yr. All of the orbits can be considered definitive; however, the total mass error for the systems remains high, mainly due to Hipparcos parallax error.

First orbits are derived for 12 new Hipparcos binary systems based on the precise speckle interferometric measurements of the relative positions of the components. The orbital periods of the pairs are between 5.9 and 29.0 yrs. Magnitude differences obtained from differential speckle photometry allow us to estimate the absolute magnitudes and spectral types of individual stars and to compare their position on the mass-magnitude diagram with the theoretical curves. The spectral types of the new orbiting pairs range from late F to early M. Their mass-sums are determined with a relative accuracy of 10-30%. The mass errors are completely defined by the errors of Hipparcos parallaxes.

The results of speckle interferometric observations of 104 binary and 6 triple stars performed at the BTA 6 m telescope in 2004 October are presented. Nearby low-mass stars are mostly observed for the program, among which 59 there are new binaries recently discovered by the Hipparcos astrometric satellite. Concurrently with the diffraction-limited position measurements we obtained 154 brightness ratio measurements of binary and multiple star components in different bands of the visible spectrum. New, first-resolved binaries are the symbiotic star CH Cyg with a weak companion at 0.043″ separation and the pair of red dwarfs, GJ 913 = HIP 118212. In addition, we derived the orbital parameters for two interferometric systems: the CN-giant pair HD 210211 = HIP 109281 (P = 10.7 yr) and the G2V-K2V G2V-K2V binary GJ 9830 = HIP 116259 (P = 15.7 yr).

We present the results of speckle-interferometric observations of the nearby triple system GJ 795 performed with the diffraction-limited resolution in the visible range at the BTA telescope. The three components of the system were optically resolved for the first time. Relative position measurements allowed to determine elements of the inner orbit of the triple. Absolute magnitudes and spectral types of the components were estimated using the measured magnitude differences: MVAa=7.31±0.08, MVAb=8.66±0.10, MVB=8.42± ±0.10, SpAa≈K5, SpAb≈K9, SpB≈K8. The total mass of the system is ƩМав = 1.69±0.27М⊕. It is shown that GJ 795 is an hierarchical triple star, which satisfies the empirical stability criteria.

On the basis of new speclinterferometric and photometric observations of eclipsing binary SZ Cam, executed on 6-m telescope at SAO RAS and 0.5-m telescope of Astronomical observatory of Ural State University, and data added from the literature, complete set of parameters of apparent relative orbit of the third body are determined for the first time. Mass of the third body M3 = 23.4M⊙ and distance up to SZ Cam d = 1125 ps are estimated. The conclusion confirming a duality of third body is made. The assumption is stated, that SZ Cam, probably, is not the member of open star cluster NGC 1502, on which centre it is projected. The values of 16 times of minima of SZ Cam are given.

The results of speckle interferometric observations of 115 metal-poor stars ([m/H] µ > 0.2 / yr, made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, are reported. Close companions with separations ranging from 0.034 to 1 were observed for 12 objects G76-21, G59-1, G63-46, G135-16, G168-42, G141-47, G142-44, G190-10, G28-43, G217-8, G130-7, and G89-14 eight of them are astrometrically resolved for the first time. The newly resolved systems include one triple star G190-10. If combined with spectroscopic and visual data, our results imply a single:binary:triple:quadruple star ratio of 147:64:9:1 for a sample of 223 primary components of halo and thick-disk stars.

Context.Because of the lack of precise masses, the coverage of the main-sequence empirical mass-luminosity relation for stars in the mass range from 0.6 to 0.9 is incomplete. The nearby K-type visual and spectroscopic binary GJ 765.2 = MLR 224 is a good candidate for new reliable points in this significant part of the relation.

Context. Because of the lack of precise masses, the coverage of the main-sequence empirical mass-luminosity relation for stars in the mass range from 0.6 M-circle dot to 0.9 M-circle dot is incomplete. The nearby K-type visual and spectroscopic binary GJ 765.2 = MLR 224 is a good candidate for new reliable points in this significant part of the relation.Aims. We have found a combined orbital solution for the pair and derived physical properties of the components using interferometric and spectroscopic data.Methods. The diffraction-limited speckle observations were mostly collected at the 6 m BTA telescope, and the velocities of the components were obtained using the CORAVEL radial velocity scanner on the Swiss 1 m telescope.Results. In a combined solution, the orbital period is found to be 11.919 yr. The masses of the GJ 765.2 components are MA = 0.831 +/- 0.020 M-circle dot and M-B = 0.763 +/- 0.019 M-circle dot. The obtained orbital parallax of the system, pi(orb) = 31.0 +/- 0.5 mas, is 7 percent lower than the Hipparcos value. The absolute V magnitudes of the stars, derived from the measured speckle magnitude differences, are: M-V(A) = 5.99 +/- 0.04 and M-V(B) = 6.64 +/- 0.05. The effective temperatures of the components, T-eff(A) = 5060 +/- 130 K and T-eff(B) = 4690 +/- 160 K, follow from the V - K and J - K color indices. The star metallicity value, estimated from the 6 m telescope spectrum, is [M/H] = - 0.35 +/- 0.15 dex.Conclusions. The presented individual masses have 2.4% and 2.5% relative accuracies. Therefore, the components of GJ 765.2 rank among a dozen stars with masses accurate to within a few percent in the mass range 0.6-0.9 M-circle dot. The existing data on the kinematics of GJ 765.2 and its chromospheric activity indicate that the binary belongs to the middle age (3-4 x 10(9) yr) thin disk population of the galaxy.

The new times in astronomy began in 1995 after discovery of planets orbiting main sequence stars. Till now over 200 planets with Jupiter-like masses have been detected. The main problem of exoplanetology to be solved is finding and study of planets which are suitable for life creation first of all Earth-like ones. Efficiency of different methods aimed to search for such planetes are analysed. It is demonstrated that Earth-like planets can be detected by apodization of their images, microlensing of backrgound stars, transits and timing of pusations of host stars. Several space-borne projects are discussed as tools of low-mass planets detections.