| |
 |
| Paper: |
Kinematics of Lithium-Rich Stars South of Taurus |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1748 |
| Authors: |
Neuhauser, R.; Frink, S.; Torres, G.; Sterzik, M. F.; Roeser, S.; Randich, S. |
| Abstract: |
We have obtained single-order echelle spectra for 106 late-type stars found with ROSAT south of Taurus, including some 30 stars that have been claimed to be low-mass pre-main sequence (PMS) stars. 19 stars are located on the Lambda Ori cloud, nine of which are K-type stars with lithium in excess of the zero-age-main-sequence (ZAMS) level; i.e., are PMS stars. At least 40 of the remaining off-cloud stars display detectable lithium, 24 of which show lithium at least as strong as IC 2602 stars with the same spectral types and, therefore, are probably not older than IC 2602 (~3 x 10^7 yr). Of those 24 stars, nine (25% of the off-cloud stars with detectable lithium) are PMS stars isolated from cloud material; all have spectral type K, and three of them are spectroscopic binaries. The remaining 15 off-cloud stars have spectral type G and lithium comparable to IC 2602 stars, i.e., may have arrived already on the ZAMS, as the G-type IC 2602 stars have. However, these 24 off-cloud lithium-excess stars are probably not older than IC 2602 (~3 x 10^7 yr). For 18 of the lithium-excess stars south of Taurus, we have determined proper motions with a typical accuracy of 5 mas/yr from the STARNET catalog, a combination of the HST GSC1.2 and the Astrographic Catalog. Most of these 18 stars have spectral type G. Their 3D space velocity is different from the 3D velocity distribution of bona-fide T Tauri stars in central Taurus. We conclude that the new G-type stars among the lithium-excess population may be young Gould Belt members. Since both the GSC and the AC are magnitude-limited, only the brightest stars (i.e., the G-type stars) are listed in STARNET. Run-away T Tauri stars, however, should be most frequent among lower-mass stars. We also discuss alternative modes of origin of the isolated PMS stars south of Taurus. |
|
|
|
|
|
