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R.S. Whitaker, E.L.N. Jensen (Swarthmore College)
As part of a long-term project to investigate planet formation, we have been conducting a survey to look for nearby low-mass pre--main-sequence stars. In the first phase of this search, we selected stars from the ROSAT and Hipparcos catalogs based on criteria that indicated a possibility of youth and measured their lithium equivalent widths and radial velocities. Here we present preliminary results from phase two of the project. We searched the Tycho-2 catalog, which is complete to fainter magnitudes than the Hipparcos catalog is, to find stars with proper motions similar to those stars we had already determined to be young. We obtained echelle spectra for 40 of these Tycho-2 stars with the 4-meter telescope at CTIO. Based on the equivalent widths of their lithium lines, we find 25 to be pre--main-sequence, including 12 double- or triple-lined spectroscopic binaries.
We present a kinematic analysis comparing these stars' space motions to those of known star-forming regions. About half of our newly-discovered young stars are projected 5--10\arcdeg outside the canonical boundaries of Upper Sco, in the Sco-Cen OB association. If these stars are between 100 and 145 pc away, their space velocities suggest membership in the Upper Sco subgroup. However, we also find stars in isolation, including one with Galactic latitude b=-85\arcdeg.
We gratefully acknowledge the support of the National Science Foundation's ``Life in Extreme Environments" program through grant AST 99-96278, and Swarthmore College through a James Michener Fellowship.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.