Name/Affiliation: Rainer Koehler (MPI for Astronomy)
Dynamical Masses of Pre-Main-Sequence Binary Systems
The mass is probably the most important parameter for the structure and evolution of a star. Therefore, empirical mass determinations are crucial for our understanding of stellar astrophysics. Binary stars are the only way to measure stellar masses directly, without relying on theoretical models. They are therefore valuable test cases for theoretical pre-main-sequence tracks. We present results of our ongoing monitoring program for orbital motion of T Tauri binaries. Their companions were discovered in the 1990s. With projected separations of 15 - 40 AU, the expected orbital periods range from 60 to 250 years. We have collected observations using speckle interferometry, adaptive optics, and lucky imaging. About 15 companions have clearly moved since their discovery, about 9 of them show signs of curvature characteristic for orbital motion. For a few of them, it is already possible to solve for a preliminary orbit solution.