An old nearby quadruple system Gliese 225.2

We discovered a new component E in the nearby multiple system Gliese 225.2, making it quadruple. We derive a preliminary 24-yr astrometric orbit of this new sub-system C,E and a slightly improved orbit of the 68-yr pair A,B. The orientations of the A,B and C,E orbits indicate that they may be close to coplanarity. The orbit of AB,CE is rather wide and does not allow to determine its curvature reliably. Thus, the 390 yr orbit computed by Baize (1980, Inf. Circ. IAU Comm., 26(80)) was premature. The infrared colors and magnitudes of components A, B, and C match standard values for dwarfs of spectral types K5V, M0V, and K4V, respectively. The new component E, 3 magnitudes below the Main Sequence, has an anomalously blue color index. We estimate its mass as roughly 0.2 solar from the astrometric orbit, although there remains some inconsistency in the data hinting on a higher mass or on the existence of additional components in the system. Large space velocities indicate that Gliese 225.2 belongs to the thick Galactic disk and is not young. This quadruple system survived for a long time and should be dynamically stable. © ESO 2005

Gliese 225.2: An old (stable?) quadruplet

We discovered with adaptive optics a new component E in the nearby multiple system Gliese 225.2, making it quadruple. We derive a preliminary 24-yr astrometric orbit of this new sub-system C,E and a slightly improved orbit of the 68-yr pair A,B. The orientations of the A,B and C,E orbits indicate that they may be close to coplanarity. The 390-yr orbit of AB,CE computed by Baize (1980) was premature, the period is much longer. Large space velocities indicate that Gliese 225.2 belongs to the thick galactic disk and is not young. This quadruple system survived for a long time and should be dynamically stable. © 2008 Springer-Verlag Berlin Heidelberg

The multiple system ADS 9626: A quadruple star or an encounter of two binaries?

© 2014, Pleiades Publishing, Ltd. The parameters of the quadruple system ADS 9626 (µ Boo) are analyzed. The system consists of two double stars: the Aa pair with an angular separation of ρ = 0.08″ and the BC pair with an angular separation of ρ = 2.2″, separated by ρ = 107″ and having the same parallaxes and proper motions. Position observations with the Pulkovo 26″ refractor have yielded from direct astrometric measurements the difference in the apparent magnitudes and the component-mass ratio for the BC subsystem: Δm = 0.59 ± 0.06, M(B)/M(C) = 1.18 ± 0.02. Spectroscopy with the Russian-Turkish 1.5-m telescope has yielded the radial velocities and physical parameters of the Aa, B, and C components. Speckle-interferometric observations with the 6-m telescope of the Special Astrophysical Observatory have provided the first measurements of the magnitude difference in the close Aa subsystem: Δm = 0.46 ± 0.03 (λ = 5500 Å) and Δm = 0.41 ± 0.03 (λ = 8000 Å). The new observations are consistent with the known orbits, which were used to find the radial velocities for the centers of mass of the inner subsystems. Themotion of the outer pair, Aa-BC, is studied using the apparent motion parameters (AMP) method. It is not possible to derive an elliptical orbit for this pair; the elements of a hyperbolic orbit have been estimated. The difference of the heavy-element abundances for the Aa and BC subsystems of 0.5 dex confirms that these pairs have a different origin. This suggests that we are observing here a close encounter of two binary stars

Multicolour CCD Measurements of Visual Double and Multiple Stars. III

Recent CCD observations were performed in the period 1998-2004 for a large sample of visual double and multiple stars selected from the Hipparcos Catalogue and/or from the Gliese Catalogue of Nearby Stars. Accurate astrometric and photometric data allowing to characterize the individual components are provided. These data are confronted to Hipparcos data or to data from an older epoch in order to assess the nature of the observed systems. We simultaneously apply a Moffat-Lorentz profile with a similar shape to all detected components and adjust the profile parameters from which we obtain the relative astrometric position (epoch, position angle, angular separation) as well as differential multi-colour photometry (filters (B)VRI). We thus acquired recent data for 71 visual systems of which 6 are orbital binaries, 27 are nearby and 30 are multiple systems. In three cases, the systems remained unresolved. 23 new components were detected and measured. Two new visual double stars of intermediate separation were also found. The estimated accuracies in relative position are 0.04 deg and 0.01" respectively, while those in differential photometry are of the order of 0.01-0.02 mag in general. The nature of the association of 55 systems is evaluated. New basic binary properties are derived for 20 bound systems. Component colours and masses are provided for two orbital binaries.Comment: 7 pages, 2 Postscript figures, 1 appendix, 1 annex containing 3 tables. Appendix A and Tables~4-6 are only available in electronic form. Astronomy and Astrophysics, in press (2006

Speckle observations with PISCO in Merate - V. Astrometric measurements of visual binaries in 2006

International audienceWe present relative astrometric measurements of visual binaries made during the first semester of 2006, with the Pupil Interferometry Speckle camera and COronagraph at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 217 new measurements of 194 objects, with angular separations in the range 0.1-4.2arcsec, and an average accuracy of 0.01arcsec. The mean error on the position angles is 0.5°. About half of those angles could be determined without the usual 180° ambiguity by the application of triple-correlation techniques. We also present a revised orbit for ADS 277 for which the previously published orbit resulted in a large residual from our measurements

Eccentricity distribution of wide binaries

ABSTRACT A sample of 477 solar-type binaries within 67 pc with projected separations larger than 50 AU is studied by a new statistical method. Speed and direction of the relative motion are determined from the short observed arcs or known orbits, and their joint distribution is compared to the numerical simulations. By inverting the observed distribution with the help of simulations, we find that average eccentricity of wide binaries is 0.59±0.02 and the eccentricity distribution can be modelled as f (e) ≈ 1.2e + 0.4. However, wide binaries containing inner subsystems, i.e. triple or higher-order multiples, have significantly smaller eccentricities with the average e = 0.52 ± 0.05 and the peak at e ∼ 0.5. We find that the catalog of visual orbits is strongly biased against large eccentricities. A marginal evidence of eccentricity increasing with separation (or period) is found for this sample. Comparison with spectroscopic binaries proves the reality of the controversial period-eccentricity relation. The average eccentricity does increase with binary period, being 0.39 for periods from 10 2 to 10 3 days and 0.59 for the binaries studied here (10 5 to 10 6 days)

Photocentric orbits from a direct combination of ground-based astrometry with Hipparcos

Complementing the Proper Motions of Fundamental Stars catalogue by Gontcharov et al. (CDS, I–266) the photocentric orbits of some FK5/Hipparcos stars are calculated in a direct combination of the Hipparcos data with astrometric ground-based observational catalogues having epochs later than 1939. Some capabilities and limitations of this method are discussed in a comparison of our results with known orbits of Sirius, Procyon, Rasalhague, μ Cas and others. We conclude that this direct combination is an acceptable tool to discover and investigate photocentric orbits with periods from 10 to 55 years and the semi-major axis of apparent ellipses >0.08 arcsec. It is particularly suitable for pairs with large magnitude difference as well as for calculation of the preliminary orbits of new astrometric binaries which will be considered in forthcoming papers. In this paper new photocentric orbits and component masses are calculated for 4 pairs: α UMa, β LMi, δ And and ξ Aqr