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R. Wichmann 1,
J. Krautter 1,
E. Covino 2,
J.M. Alcalá 3, 4,
R. Neuhäuser 3 and
J.H.M.M. Schmitt 3
Received 25 April 1996 / Accepted 26 September 1996
In a recent study, some 130 new weak-line T Tauri stars (WTTS) have been discovered in the Lupus star forming region (SFR). Some of these stars are seen projected onto regions of high obscuration, while others are located far from the Lupus dark clouds. In this paper we present photometric observations of a large sample of these WTTS. We estimate effective temperatures and luminosities for the stars observed, and derive masses and ages by comparison with theoretical evolutionary tracks. The mean age of WTTS seen in projection against the dark clouds is found to be lower than the mean age of WTTS discovered far from regions of high obscuration, and yet higher than the mean age of the classical T Tauri stars (CTTS) in Lupus. Moreover, while the CTTS in Lupus show an unusual predominance of very low-mass stars, the WTTS population in Lupus contains many stars with comparatively higher masses. Correlations between the X-ray emission and other stellar parameters, like bolometric luminosity, radius, mass, and age, are studied, and the results are discussed.
Key words: stars: formation stars: late-type stars: pre-main sequence X-rays: stars
* Based on observations collected at European Southern Observatory, Chile (observing proposals ESO 50.7-0110, 53.7-0085).
Send offprint requests to: R. Wichmann
Online publication: July 3, 1998