Late-type field stars in the RASS at high galactic latitude
Franz-Josef Zickgraf (Hamburger Sternwarte)
Joachim Krautter (Landessternwarte Heidelberg)
Sabine Frink (Sterrewacht Leiden)
We present results of an investigation of a high-galactic
latitude sample of late-type field stars detected in X-rays
during the ROSAT All-Sky Survey (RASS). The sample comprises
≈200 G, K, and M stars. Lithium abundances were determined
for ≈180 G-M stars. Radial velocities were measured for
the ≈140 G and K type stars of the sample. Combined with
proper motions these data were used to study the age
distribution and the kinematical properties of the sample.
Based on the lithium abundances half of the G-K stars were
found to be younger than the Hyades (660Myr). A small
subsample of 10 stars is younger than the Pleiades (100Myr).
They are therefore most likely pre-main sequence stars.
Kinematically the PMS stars appear to form a group
with space velocities close to the Castor moving group but
clearly distinct from the Local Association.