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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).
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