Huélamo, N., Neuhäuser, R., Fernández, M., and Wolk, S. J.
Astronomische Gesellschaft Abstract Series, Vol. 18., Abstracts of Contributed Talks and Posters presented at the Annual Scientific Meeting of the Astronomische Gesellschaft at the Joint European and National Meeting JENAM 2001 of the European Astronomical Society and the Astronomische Gesellschaft at Munich, September 10-15, 2001, abstract #MS 07 04.
Post-T Tauri stars (PTTS) are pre-Main Sequence (PMS) late-type stars approaching the Main Sequence (MS). Given their evolutionary stage, intermediate between the T Tauri phase and the Zero Aged Main Sequence (ZAMS), the rotational properties of PTTS are crucial to understand the evolution of angular momentum in PMS late-type stars. However, previous studies have failed in deriving the overall rotational properties of PTTS mainly because the samples were X-ray selected, resulting in a biased towards fast rotators. We have been able to isolate an unbiased sample of PTTS using a different selection criteria: we have studied binary systems comprised of MS early-type stars (with ages ~107 yrs) and late-type secondaries. Given the ages of the primaries and if the systems are bound, the companions could be PTTS. The presence of indicators of youth among the secondaries have confirmed their PMS nature. Our main goal is to derive the rotational properties of this unbiased sample of PTTS, so we have already monitored the stars during 10 consecutive nights in five optical filters (UBVRI). In order to derive their periods, we are studying rotational modulations in their lightcurves due to the presence of spots on their surfaces. We plan to present our preliminary results on their rotational properties.