Max-Planck-Institut für extraterrestrische Physik
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T Tauri Stars
Large samples discovered by ROSAT outside the classical star formation region
We search for low-mass pre-main sequence (PMS) stars, so-called T Tauri stars (TTS), among the large sample of unidentified ROSAT All-Sky Survey sources by means of ground-based optical follow-up observations. ROSAT source counterparts with Halpha emission and Lithium 6707 Å absorption together with a late spectral type (late F to M) can be regarded as young stars, as Lithium is burned in low-mass, i.e. fully convective, stars during the first few million years by proton-proton caption at the bottom of the convection zones.
For the newly identified young stars, we can then try to estimate their ages in two different ways:
1. Doing UBVRI photometry for estimating the bolometric luminosity and the effective temperature, so that we can place the stars into the Hertzspung-Russell diagram. Then, we can compare their location with theoretical isochrones and evolutionary tracks to estimate ages and masses. This has been done in the Chamaeleon star forming region (see Fig. 1).
R. Neuhäuser (1997) Science 276, 1363-1370
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