Thesis Topic: Optical-Infrared Studies of Planet Formation Around Intermediate-Mass Stars


Thesis Supervisors: Mario van den Ancker




One of the most important developments in astronomy over the last decades has been the discovery of planetary systems in stars other than our own sun. At present, more than 200 such exo-planets are known, presenting a staggering diversity in planetary architectures. The reason for this diversity is presently unknown, but is suspected to be related to differences in their formation history, and the different processes that act to dissipate the disks around young stars from which these planets have formed.

The subject of the PhD topic offered here is a systematic study of planet- forming disks and their host stars using high-resolution spectroscopy for a large (~ 100) sample of intermediate-mass young stars, possessing disks in a variety of stages of dissipation, that has been obtained with the UVES (optical), X-Shooter (UV + Optical + near-infrared) and CRIRES (infrared) spectrographs at ESO's Very Large Telescope. The first part of the thesis research will consist of reducing and analyzing these data, and possibly supplementing these data with further observations, if necessary. Physical parameters of the stellar photosphere will be determined by fitting stellar atmosphere models to the spectra. A variety of indicators of gas (e.g. H I, H2, CO, water) in the disks present in these spectra will be studied. Ultimate goal of this part of the research is to determine the relative importance of the various disk dissipation mechanisms that have been proposed in the literature.

The second half of the thesis research will consist of developing and applying theoretical models for disk dissipation and planet formation. The model will be applied to an ensemble of stars, using the distribution of initial conditions from the observational sample studied in part, to predict the final outcome of the planet-forming process in intermediate-mass stars. Results will be compared to observed properties of exoplanetary systems, and will ultimately be employed to get closer to answering the question how common the architecture of our own solar system is.

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