International audiencePreliminary new orbital elements were computed for the visual binary stars A 1 - ADS 1345, A 2629 - ADS 3610, BU 560 - ADS 4371, STF 3115 - ADS 4376, STF 1426 AB - ADS 7730 and STF 2437 - ADS 11956. Using Straizys and Kuriliene's data, we derived new formulae for computing dynamical parallaxes for luminosity classes IV and V. The values found for those systems are in agreement with the {Hipparcos} parallaxes and the corresponding systemic masses are consistent with the spectral types

This paper presents speckle observations of Mira (o Cet) and late-type stars with the PISCO speckle camera of Pic du Midi during the period 1995-1998. A survey for binarity among a sample of late-type stars was performed, which led to 7 positive detections out of 36 objects. Photometric and color variations of the companion of Mira were searched for, but no significant brightness variations could be found over a time scale of ∼5-10 minutes. The position and photometry measurements, the restored images with high angular resolution of the binary system Mira A-B (ADS 1778) are in full agreement with HST data obtained at the same epoch. A new orbit has been derived for Mira A-B.

In the context of the programme Global Architecture of Planetary Systems (GAPS), we have performed radial velocity monitoring of the metal-poor star HIP 11952 on 35 nights during about 150 days using the newly installed high-resolution spectrograph HARPS-N at the TNG and HARPS at the ESO 3.6 m telescope. The radial velocities show a scatter of 7 m s −1 , compatible with the measurement errors for such a moderately warm metal-poor star (T eff = 6040 ± 120 K; [Fe/H] = −1.9 ± 0.1). We exclude the presence of the two giant planets with periods of 6.95 ± 0.01 d and 290.0 ± 16.2 d and radial velocity semi-amplitudes of 100.3 ± 19.4 m s −1 and 105.2 ± 14.7 m s −1 , respectively, which have recently been announced. This result is important because HIP 11952 was thought to be the most metal-poor star hosting a planetary system with giant planets, which challenged some models of planet formation.

Abstract. We present speckle observations of 48 double and multiple stars observed with the 2-meter "Télescope Bernard Lyot" (TBL) in December 1995, January 1997 and June 1997. Angular separations, absolute position angles and relative photometry result from these observations. New orbital elements have been recalculated for 8 double stars.

International audienceWe present relative astrometric measurements of visual binaries made during the second semester of 2005, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long term program is to improve the accuracy of the orbits and determine the masses of the components.\ We performed 130 new observations of 120 objects, with most of the angular separations in the range 0\farcs1-4\arcsec, and with an average accuracy of 0\farcs01. Most of the position angles could be determined without the usual 180° ambiguity with the application of triple-correlation techniques, and their mean error is 0\fdg8. We have found a possible new triple system: ADS 11077. ?kip0.15cm The measurements of the closest binaries were made with a new data reduction procedure, based on model fitting of the background of the auto-correlations. As this procedure proved to be very efficient, we have re-processed the old observations of close binaries made with PISCO in Merate since 2004. We thus improved 20 measurements already published and obtained 7 new measurements for observations that were previously reported as ``unresolved".\ We finally present revised orbits for ADS 684, MCA 55Aac (in the Beta 1 Cyg-Albireo multiple system) and ADS 14783 for which the previously published orbits led to large residuals with our measurements and for which the new observations made since their computation allowed a significant improvement of those old orbits. The sum of the masses that we derived for those systems are consistent with the spectral type of the stars and the dynamic parallaxes are in good agreement with the parallaxes measured by Hipparcos

We present relative astrometric measurements of visual binaries made with the Pupil Interferometry Speckle camera and Coronagraph (PISCO) at the 1‐m Zeiss telescope of Brera Astronomical Observatory, in Merate. We provide 135 new observations of 103 objects, with angular separations in the range 0.1–4.0 arcsec and with an accuracy better than ∼0.01 arcsec. Our sample is made of orbital couples as well as binaries whose motion is still uncertain. Our purpose is to improve the accuracy of the orbits and constrain the masses of the components. This work already leads to the revision of the orbits of three systems (ADS 5447, 8035 and 8739).

International audienceWe present relative astrometric measurements of visual binaries made during the first semester of 2005, with the Pupil Interferometry Speckle Camera and Coronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate. We performed 214 new observations of 192 objects, with angular separations in the range 0.2-4.3arcsec, and with an average accuracy of 0.01arcsec. Most of the position angles could be determined without the usual 180° ambiguity, and their mean error is . Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long-term programme is to improve the accuracy of the orbits and constrain the masses of the components. For the first time with PISCO, the astrometric calibration was made with a grating mask mounted at the entrance of the telescope. The advantage of this procedure is to provide a reliable and fully independent scale determination. We have found two possible new triple systems: ADS 7871 and KUI 15. We propose a preliminary orbit for ADS 4208

We present a new orbit for the visual binary ADS 8630 = γ Vir. Although it is one of the first visual double stars discovered, its orbital elements were still poorly known. Indeed the very high eccentricity of the orbit and the difficulty of observing the pair at periastron passage in 1836 has meant that it is only now that sufficient measures of the recent close approach in 2005 have allowed an orbital analysis which predicts the angular motion to an acceptable degree of accuracy. We also investigate in detail the possibility of the presence of a third body in the system, that was proposed by other authors. The high-angular resolution infra-red image of γ Vir that we obtained in June 2006 with the LuckyCam instrument on the ESO NTT shows the absence of any companion as faint as a M0V star at a distance larger than 0. 4. Combined with the analysis of the residuals of our orbit, the values found for the masses of the individual components and the radial velocity measurements, this observation rules out the presence in the system of a third companion with a mass larger than 0.3 M .