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Figure 7: Continuum images of the observed stars. Contour steps are -4, -2, 2, 4, 6, 8 and then 10 to 50 by 5 mJy/beam. The name of the source is indicated in upper left corner, and the beam size in lower left. The crosses indicate the nominal position of the stars from HBC. Coordinates are in the J2000 system. Positions have been corrected for proper motions according to measurements by Jones and Herbig (1979) and Hartmann et al. (1991).
Figure 8: Continuum images of the observed stars (cont.). The upper limits for IW Tau, IS Tau, GH Tau, GK Tau and LkCa 3 (not shown here) were obtained with a beam similar to that of DM Tau. For UY Aur, we show two maps, one obtained at full resolution (left), the other (right) done with a 150-m taper. Since Haro 6-5b is displaced from the pointing center FS Tau, the map has been corrected from the primary beam attenuation. The S/N in this map decreases towards the north-west of the map, and contours to the north and north-west of Haro 6-5b are noise peaks. Note that GM Aur position has not been corrected for proper motion.
We detected 2.7 mm continuum emission in 12 systems at S/N >5 and have probable detections for another 5. V 773 Tau, a weak emission line binary system, is remarkable in that its 2.7 mm continuum decreased from mJy to mJy in less than six months. We find that the singles are, on average, stronger 2.7 continuum sources than the multiples, consistent with Osterloh & Beckwith's (1995) finding at 1.3 mm. Significant estimates of the sizes have been obtained for 8 singles. They imply large (R > 150 AU) disks, with relatively flat density distribution (emissivity flatter than ). The spectral energy distributions in the millimeter range can be fitted using a dust emissivity law with value of in the range 0.5 to 1.
Only DG Tau, Haro 6-5b and UY Aur have detectable emission. emission, but no 2.7 mm continuum, is also found in the LkH 332 region and near FS Tau; however, it does not appear to be associated with the known stars. Interpreting the observational results in terms of the circumstellar disk scenario, we find that, in all cases, disk masses derived from the dust emission at 2.7 mm are more than a factor of about 20 larger than the masses derived from the upper limit.
To appear in A&A main journal.
is available as a postscript file.