Astron. Astrophys. 330, 549-558 (1998)

Millimeter continuum observations of X-ray selected T Tauri stars in Ophiuchus ^*

Dieter Nürnberger ¹, Wolfgang Brandner ^{1, 2}, Harold W. Yorke ¹ and Hans Zinnecker <sup>3

1</sup> Astronomisches Institut der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
(nurnberg@astro.uni-wuerzburg.de), (brandner@astro.uni-wuerzburg.de), (yorke@astro.uni-wuerzburg.de)
² Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801, USA
(brandner@astro.uiuc.edu)
³ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany (hzinnecker@aip.de)

Received 13 March 1997 / Accepted 22 September 1997

Abstract

We present the results of 1.3 mm dust continuum observations for a sample of 17 X-ray selected T Tauri stars in the Ophiuchus star forming region performed with the MPIfR 7-channel bolometer array mounted at the IRAM 30 m Millimeter Radio Telescope. We have detected cold dust emission from 3 of the objects and have derived 3 upper limits ( 21 mJy on average) for the remaining objects. These upper limits suggest that the disk masses (gas dust) are less than 5 10^-3 M .

Combining our results with those obtained by André & Montmerle (1994) for a sample of 21 X-ray selected T Tauri stars (3 additional detections) we improve the statistical significance of our conclusions. As the frequency of circumstellar disks and the disk properties might depend on the selection criteria as well as local conditions, comparison is made with 1.3 mm surveys of H selected T Tauri stars in Chamaeleon, Lupus, Ophiuchus, and Taurus-Auriga.

In order to study the mass of cold dust in multiple systems we also observed a sample of 15 well known binaries, triples, and quadruples by 1.3 mm photometry. From these observations we report the 1.3 mm detection of 4 multiple systems. It seems that the measured 1.3 mm flux density increases slightly with increasing binary separation.

In addition, we have mapped the hierarchical triple SR 24 at = 1.3 mm with the 7-channel bolometer array. We detected cold dust emission only from the southern component with a peak intensity of 230 mJy and a corresponding circumstellar disk mass of 0.035 M (gas dust), while for the northern component we derived an upper limit of 10 of the SR 24S peak flux density. The non-detection of 1.3 mm emission from SR 24N suggests a lack of cold circumstellar dust in the outer part of the disk, which might have been cleared by the close infrared companion away from SR 24N.

Key words: stars: circumstellar matter stars: formation stars: late-type stars: low-mass stars: pre-main sequence radio continuum: stars

* Based on observations obtained with the IRAM 30 m MRT on Pico Veleta, Spain

Send offprint requests to: Dieter Nürnberger

© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
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