Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Abstract

The star-forming regions in Chamaeleon are one of the nearest (distance ~165 pc) and youngest (age ~2 Myrs) conglomerates of recently formed stars and the ideal target for population studies of star formation. We investigate a total of 16 Cha targets, which have been suggested, but not confirmed as binaries or multiple systems in previous literature. We used the adaptive optics instrument Naos-Conica (NACO) at the Very Large Telescope Unit Telescope 4 of the Paranal Observatory, at 2-5 different epochs, in order to obtain relative and absolute astrometric measurements, as well as differential photometry in the J, H, and K band. On the basis of known proper motions and these observations, we analyse the astrometric results in our "Proper Motion Diagram" (PMD: angular separation / position angle versus time), to eliminate possible (non-moving) background stars, establish co-moving binaries and multiples, and search for curvature as indications for orbital motion. All previously suggested close components are co-moving and no background stars are found. The angular separations range between 0.07 and 9 arcseconds, corresponding to projected distances between the components of 6-845 AU. Thirteen stars are at least binaries and the remaining three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order multiple systems with up to four components. In 13 cases, we found significant slopes in the PMDs, which are compatible with orbital motion whose periods range from 60 to 550 years. However, in only four cases there are indications of a curved orbit, the ultimate proof of a gravitational bond. Massive primary components appear to avoid the simultaneous formation of equal-mass secondary components. (abridged)

33 pages, 22 figures, accepted for publication in A&A, 2nd version: typos and measurement unit added in Table 2

References in corpus (11)

• The Stellar Population of the Chamaeleon I Star-Forming Region
• The Disk Population of the Chamaeleon I Star-Forming Region
• PPM-Extended (PPMX) - a catalogue of positions and proper motions
• A VLT/NACO Survey for Triple and Quadruple Systems among Visual Pre-Main Sequence Binaries
• Pre-main sequence spectroscopic binaries suitable for VLTI observations
• Direct evidence of a sub-stellar companion around CT Cha
• A Multiplicity Census of Young Stars in Chamaeleon I
• Binary frequency of very young brown dwarfs at separations smaller than 3 AU
• Astrometric and photometric monitoring of GQ Lup and its sub-stellar companion
• Edge-on disk around the T Tauri star [MR81] Halpha 17 NE in CrA
• Confirmation of the binary status of Cha Halpha 2 - a very young low-mass binary in Chamaeleon

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