A Connection Between Submillimeter Flux and Binary\\ Separation II. The Scorpius-Ophiuchus Star-Forming Region

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Session 44 -- Young Stars, T Tauri Stars, Herbig Haro Objects
Display presentation, Wednesday, 1, 1994, 9:20-6:30

[44.09] A Connection Between Submillimeter Flux and Binary\\ Separation II. The Scorpius-Ophiuchus Star-Forming Region

E.L.N. Jensen, R.D. Mathieu (U. of Wisconsin), G.A. Fuller (NRAO)

We have used the James Clerk Maxwell Telescope to make a sensitive 800-$\mu$m continuum survey of most of the pre-main sequence (PMS) binaries in the Scorpius-Ophiuchus star-forming region with projected separations $\alt 150$ AU\null. Combining our observations with the 1300-$\mu$m survey by Andr\'e \& Montmerle (1994, ApJ 420, 837), we find that $\sim 50\%$ of binaries with projected separations $a \agt 50$ AU were detected, whereas only 1 out of 8 binaries with $1 \alt a \alt 50$ AU was detected. This agrees with the suggestion of Beckwith et al.\ (1990, AJ 99, 924) and with our previous results for Taurus binaries (Jensen, Mathieu, \& Fuller 1994, ApJLett , in press): the presence of a binary with a separation of a few tens of AU seems to influence the structure of the disk. The binary may reduce the submillimeter flux either by reducing the surface density throughout the disk or by dynamically clearing a gap in the disk, thereby reducing the emitting surface area.

Our new observations include 8 spectroscopic binaries with $a < 1$ AU, a regime not well-probed by previous observations. We detected submillimeter continuum emission from two of these binaries, AK Sco and V4046 Sgr. Along with the strong submillimeter detection of GW Ori (Mathieu et al.\ 1994, {\it AJ}, in press), our results indicate that substantial circumbinary disks can exist around the closest binaries. The detections indicate that close binaries do not dynamically disperse associated circumbinary disks prior to the pre-main sequence stage. Nonetheless, the detections are consistent with dynamical clearing around the stellar orbits since these close binaries would not clear large portions of their disks. However, we note that the inferred disk mass for AK Sco is comparable to the lowest disk masses detected by Beckwith et al.\ among PMS stars, and we did not detect the other six PMS spectroscopic binaries in Scorpius-Ophiuchus with typical 3$\sigma$ limits $F_{\nu,\, 800\, \mu{\rm m}} \le 25$ mJy. Thus, it remains unclear whether the disk properties of the closest binaries are similar to those of wider binaries and single stars.

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