Abstract. We present the results of diffraction-limited optical speckle interferometry and infrared bispectrum speckle interferometry of 111 double and 10 triple systems performed in 1998-1999 with the 6-m telescope of the Special Astrophysical Observatory in Zelenchuk. The observations concentrated on nearby close binaries discovered during the Hipparcos mission. Many nearby fast-orbiting low-mass binaries known before Hipparcos were also included in the program. New companions were first resolved in 4 systems: HIP 5245, ADS 3179, Kui 99, and ADS 16138. In addition to accurate relative positions, magnitude differences were measured for most of the pairs. We combined our results with the Hipparcos parallaxes to derive absolute magnitudes and spectral types for 63 binaries and 4 triples. Preliminary orbital elements and the mass-sum are derived for HIP 689, and improved orbits are presented for HIP 16602 (CHR 117) and HIP 21280 (CHR 17).

Abstract. 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 binary GJ 9830 = HIP 116259 (P=15.7 yr).

Abstract. We present first orbits for 6 new Hipparcos binaries. The orbits were determined from speckle interferometric measurements collected mainly at the 6 m BTA telescope of the Special Astrophysical Observatory in Zelenchuk. Three of the systems, HIP 11352, HIP 14075 and HIP 14230, have late G-or early K-type components, while HIP 14669 = GJ 125, HIP 106972 = GJ 4210 and HIP 111685 = GJ 4287 have M-type components. The periods of the orbits are in the range of 6−28 years. Mass sums and their errors are derived for the systems. The Hipparcos parallax error is the dominating error source of the mass determination.

Abstract. This paper is a continuation of diffraction-limited speckle interferometry of binary and multiple stars carried out at the 6-m telescope of the Special Astrophysical Observatory in Zelenchuk. The program has concentrated on nearby (π > 10 mas) close binaries discovered or measured during the Hipparcos mission. Here, we present 132 measurements of relative positions and magnitude differences for 99 pairs and 8 measurements for 6 triple systems. 54 entries in the paper are new Hipparcos binaries. New triple systems with late-type dwarf components, discovered in the course of observations, are HIP 8533 and HIP 25354.

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.