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A lunar occultation and direct imaging survey of multiplicity in the Ophiuchus and Taurus star-forming regions
Simon, M.; Ghez, A. M.; Leinert, Ch.; Cassar, L.; Chen, W. P.; Howell, R. R.; Jameson, R. F.; Matthews, K.; Neugebauer, G.; Richichi, A.
AA(State University of New York, Stony Brook, NY, US), AB(State University of New York, Stony Brook, NY, US), AC(Max-Planck-Institut für Astronomie, Heidelberg, Germany), AD(Max-Planck-Institut für Astronomie, Heidelberg, Germany), AE(National Central University, Chung-Li, Taiwan), AF(National Central University, Chung-Li, Taiwan), AG(University of Wyoming, Laramie, WY, US), AH(University of Wyoming, Laramie, WY, US), AI(California Institute of Technology, Pasadena, CA, US), AJ(California Institute of Technology, Pasadena, CA, US)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 443, no. 2, p. 625-637 (ApJ Homepage)
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NASA/STI Keywords:
Binary Stars, Infrared Astronomy, Lunar Occultation, Ophiuchi Clouds, Pre-Main Sequence Stars, Star Formation, Taurus Constellation, Angular Momentum, Cameras, Infrared Imagery, Stellar Color
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We present an IR lunar occultation and direct imaging search for companions in the Ophiuchus star-forming region and update a similar search of the Taurus region. The search is sensitive to companions in the angular separation range 0.005-10 sec. In Ophiuchus, we surveyed 35 young star targets; this sample contains at least 10 binaries, two triples, and one quadruple. Ten of the companion stars are newly discovered. In Taurus, the survey now includes 47 systems among which there are at least 22 binaries and four triples. Only two companion stars are newly identified because there is strong overlap with prior work. All the triples and quadruple are hierarchical. The observed binary frequency in Ophiuchus, in the 3-1400 AU range of separations, is at least 1.1 +/- 0.3 that of the nearby solar-like stars. This value is a lower bound because we make no corrections for incompleteness. In Taurus, in the same range of separations, the observed binary frequency is at least 1.6 +/- 0.3 that of the nearby solar-like stars. This value extends Ghez et al.'s (1993) and Leinert's et al.'s (1993) determination of an excess binary frequency to 3 AU separation. We used the weak-line T Tauri star/T Tauri star (WT/TT) type and the K-L color index to distinguish between systems with and without inner disks. We find no convincing difference in the binary frequency or distribution of separations of the systems with and without inner disks. The 1.3 mm continuum emission of the single systems exceeds that of the multiples suggesting that their extensive outer disks are more massive. The specific angular momenta of the binaries overlap those of molecular cloud cores measured by Goodman et al. (1993).

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