Search for planets around young stars with the radial velocity technique

Abstract

Giant planets form in circumstellar disks around young stars. Two alternative theoretical formation concepts, disk instability and core accretion, may both apply under certain conditions, but core accretion is believed to be the main mechanism. No observational proof of the dominant process has been found thus far. Therefore, this thesis aims to detect sub-stellar companions orbiting young stars (1–100 Myr), because characteristics of young planets give input on formation processes involved. For this thesis, echelle spectra of 100 young stars have been obtained and analysed for vsini and basic stellar parameters. The radial-velocity has been calculated by cross-correlation of the spectra with templates using MACS. Stellar activity has been characterized by the analysis of the line bisector and other indicators. For 12 of the analysed stars, the radial-velocity variation is most likely caused by rotational modulation of stellar activity. Furthermore, one brown dwarf and six giant planets orbiting stars with ages of 2–90 Myr have been found. However, the ages of the stars are ill constraint and the number of found sub-stellar companions is too low to draw serious conclusions for formation processes. The frequency of giant planets and brown dwarfs around young stars is comparable to the frequency around solar-like stars.