EDP Sciences
Free Access
Volume 437, Number 2, July II 2005
Page(s) 611 - 626
Section Stellar structure and evolution
DOI https://doi.org/10.1051/0004-6361:20042107

A&A 437, 611-626 (2005)
DOI: 10.1051/0004-6361:20042107

A multiplicity survey of the $\rho$ Ophiuchi molecular clouds

T. Ratzka1, R. Köhler1, 2 and Ch. Leinert1

1  Max-Planck-Institute for Astronomy (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: ratzka@mpia.de
2  Sterrewacht Leiden, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands

(Received 1 October 2004 / Accepted 22 March 2005)

We present a volume-limited multiplicity survey with magnitude cutoff ( ${m}_{K}\leq 10.5\mathrm{\ mag}$) of 158 young stellar objects located within or in the vicinity of the $\rho$ Ophiuchi Dark Cloud. With exception of eleven already well observed objects, all sources have been observed by us in the K-band with 3.5 m telescopes by using speckle techniques. The separation range covered by our survey is $0.13''\leq\theta\leq 6.4''$, where the lower limit is given by the diffraction limit of the telescopes and the upper limit by confusion with background stars. The multiplicity survey is complete for flux ratios $\geq $0.1 ( $\Delta{m}_{K}\leq 2.5$) at the diffraction limit. After taking the background density into account the degree of multiplicity is $29.1\%\pm 4.3\%$ and thus only marginally higher than the value $23.5\%\pm 4.8 \%$ derived for the given separation range for the main-sequence solar-like stars in the solar neighbourhood (Duquennoy & Mayor 1991). We discuss the implications of these findings.

Key words: stars: pre-main-sequence -- binaries: visual -- infrared: stars -- surveys -- techniques: interferometric

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© ESO 2005