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Subsystems in Nearby Solar-type Wide Binaries
We conducted a deep survey of resolved subsystems among wide binarieswith solar-type components within 67 pc of the Sun. Images of 61 starsin the K and H bands were obtained with the Near-Infrared CoronagraphicImager adaptive-optics instrument on the 8 m Gemini-South telescope. Ourmaximum detectable magnitude difference is about 5 mag and 7.8 mag at0farcs15 and 0farcs9 separations, respectively. This enables a completecensus of subsystems with stellar companions in the projected separationrange from 5 to 100 AU. Out of seven such companions found in oursample, only one was previously known. We determine that the fraction ofsubsystems with projected separations above 5 AU is 0.12 ± 0.04and that the distribution of their mass ratio is flat, with a power-lawindex of 0.2 ± 0.5. Comparing this with the properties of closerspectroscopic subsystems (separations below 1 AU), it appears that themass-ratio distribution does not depend on the separation. The frequencyof subsystems in the separation ranges below 1 AU and between 5 and 100AU is similar, about 0.15. Unbiased statistics of multiplicity higherthan 2, advanced by this work, provide constraints on star formationtheory.Based on observations obtained at the Gemini Observatory (Program IDGS-2009B-Q-49), which is operated by the Association of Universities forResearch in Astronomy, Inc., under a cooperative agreement with theNational Science Foundation on behalf of the Gemini partnership: theNational Science Foundation (United States), the Science and TechnologyFacilities Council (United Kingdom), the National Research Council(Canada), CONICYT (Chile), the Australian Research Council (Australia),Ministério da Ciência e Tecnologia (Brazil), and Ministeriode Ciencia, Tecnología e Innovación Productiva(Argentina).
| CCD astrometry and components instrumental magnitude difference of 432 Hipparcos wide visual double stars
Context: We measured the angular separations, position angles, ΔV, Δ y and Δ I of wide visual double stars during the period2003-2005. At least one component of the double stars in our sample hasan entry in the Hipparcos catalogue. Aims: Our measurements are acontribution to the study of the nature of these double stars. Methods: The northern double stars of the project were observed with the1.2 m telescope of the Kryonerion observatory and the southern with the1.0 m SAAO. We performed multiple-exposure CCD imaging of our targetsand used the standard procedure of data reduction and astrometric CCDcalibrations. Results: We present measurements of 213 northern and 219southern wide binaries.Based on observations made at Kryonerion Observatory of the NationalObservatory of Athens, Greece, and the South African AstronomicalObservatory. Full Table 1 and Tables 2, 3 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/472/1055
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