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E. L. N. Jensen, K. J. Schlesinger, C. T. Higby-Naquin (Swarthmore College)
Recent observations have shown that a substantial population of pre-main-sequence stars exists within 100 pc of the Sun. Such stars are useful for constraining disk evolution timescales, given their relative proximity and their ages in the 10--50 Myr range, filling the gap between nearby low-mass star-forming regions with ages of a few Myr and ZAMS stars at ages of 100 Myr. We present here the latest results from our continuing search for such stars.
In this work, we have undertaken a search for young stars too faint to be included in the Hipparcos catalog by looking for x-ray bright Tycho-2 stars with kinematics similar to the young Hipparcos stars HIP 33111, 33455, 46063, and 48558. These stars lie in the vicinity of (but outside the conventional boundaries of) the Lower Centaurus Crux (LCC) OB association and the ~30 Myr-old open cluster IC 2391. There is significant overlap between the stars selected here and those proposed by Makarov & Urban (2000) as the Carina-Vela moving group, though the stars around HIP 33111 and 33455 lie outside the proposed moving group, and also farther from LCC.
We present high-resolution optical spectra of more than 60 such stars, from which we derive Li abundances, surface gravities, and precise radial velocities. Many of these stars are late-type pre-main-sequence stars, showing strong x-ray emission (log Lx/Lbol > -4) and strong Li absorption at levels similar to the late-type stars in IC 2602 and IC 2391. Most of the stars that show strong Li absorption also share similar radial velocities, clustering around vhelio \approx +20 km/s.
We present a detailed analysis of these stars' ages and kinematics, and we discuss their relationship to the other young stars and known star-forming regions in the vicinity.
We gratefully acknowledge the support of this work by the National Science Foundation, through grant AST-0307830.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.