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A lunar occultation and direct imaging survey of multiplicity in the Ophiuchus and Taurus star-forming regions

Simon, M. and Ghez, A. M. and Leinert, Ch. and Cassar, L. and Chen, W. P. and Howell, R. R. and Jameson, R. F. and Matthews, K. and Neugebauer, G. and Richichi, A. (1995) A lunar occultation and direct imaging survey of multiplicity in the Ophiuchus and Taurus star-forming regions. Astrophysical Journal, 443 (2). pp. 625-637. ISSN 0004-637X. doi:10.1086/175554.

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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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Ghez, A. M.0000-0003-3230-5055
Additional Information:© 1995 American Astronomical Society. Received 1994 May 18; accepted 1994 October 28. We thank the Time Allocation Committees and Directors of the AAT, Calar Alto, Kitt Peak, La Palma, NASA-IRTF, Palomar, and WIRO observatories for the time allocations that made this research possible. We thank the staffs of these observatories who supported us in making these observations. M. S. thanks Bruce Wilking and Bob Mathieu for scrutinizing Tables 2 and 6 and for comments on cluster membership; Rwei-Ju Chuang and Nancy Mendell for advice on statistics; and Lisa Prato for careful readings of early drafts. We thank Bob Mathieu, the referee, for urging us to sharpen the arguments in §§ 4.3 and 4.4 and suggesting the numerical experiment. A. G.'s work is supported by NASA through grant HF1031.92A awarded by the Space Telescope Science Institute which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. Infrared astrophysics at Palomar is supported by a grant from the NSF. M. S.'s work is supported in part by NSF grant AST 91-4606.
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NASANAS 5-26555
NSFAST 91-4606
Subject Keywords:binaries: visual occultations open clusters and associations: general stars: pre-main-sequence
Issue or Number:2
Record Number:CaltechAUTHORS:20180130-133716531
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Official Citation: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. Astrophysical Journal, Part 1 vol. 443, no. 2, p. 625-637
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84585
Deposited By: Ruth Sustaita
Deposited On:31 Jan 2018 18:14
Last Modified:15 Nov 2021 20:21

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