Chemical signatures of planet formation in field and open cluster stars

Abstract

In this thesis, I have conducted a strictly line-by-line differential abundance analysis using high resolution, high signal-to-noise ratio spectra of field stars (e.g., stellar binaries, terrestrial planet hosts etc.) and open cluster stars (e.g., theHyades stars) in order to identify the chemical signatures of planet formation. My research can help to answer a few fundamental questions: does planet formation affect the chemical composition of the host stars and does stellar birth environment affect the formation of planet? This thesis also has ramifications for Galactic archeology since I measured accurate abundances in a benchmark open cluster and identified, for the first time, real star-to-star abundance variations in any open cluster. These results present a new challenge to the current view of Galactic archaeology. The three main results from this thesis are: First, we present a high-precision, differential abundance analysis of the HAT-P-1 stellar binary. The secondary star in this double system is known to host a transiting giant planet while no planets have yet been detected around the primary star. The derived elemental abundances of the primary and secondary stars are identical within the errors. The striking similarity in the chemical compositions of the two stellar components in HAT-P-1 indicates that the formation of giant planets does not necessarily imply differences in the chemical abundances of the host stars. The elemental abundances of each star in HAT-P-1 relative to the Sun show an identical, positive correlation with the condensation temperature, thus we speculate based on the scenario put forward by Melendez et al. (2009) that HAT-P-1 experienced less efficient formation of terrestrial planets than the Sun. This would be in line with the expectation that the presence of close-in giant planets prevents the formation or survival of terrestrial planets. Secondly, in order to further examine the possibility of planet formation imprinting chemical signatures in the host star, we conduct a detailed differential abundance analysis of the