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Abstract
Nearby young stars are without equal as stellar and planetary evolution laboratories. The aim of this work is to use age diagnostic considerations to execute a complete survey for new nearby young stars and to efficiently reevaluate and constrain their ages. Because of their proximity and age, young, nearby stars are the most desired targets for any astrophysical study focusing on the early stages of star and planet formation.Identifying nearby, young, low-mass stars is challenging because of their inherent faintness and age diagnostic degeneracies. A new method for identifying these objects has been developed, and a pilot study of its effectiveness is demonstrated by the identification of two definite new members of the TW Hydrae Association. Nearby, young, solar-type stars are initially identified in this work by their fractional X-ray luminosity. The results of a large-scale search for nearby, young, solar-type stars is presented. Follow-up spectroscopic observations are taken in order to measure various age diagnostics in order to accurately assess stellar ages. Age, one of the most fundamental properties of a star, is also one of the most difficult to determine. While a variety of procedures have been developed and utilized to approximate ages for solar-type stars, with varying degrees of success, a comprehensive age-dating technique has yet to be constructed. Oftentimes, different methods exhibit contradictory or conflicting findings. Such inconsistencies demonstrate the value of a uniform method of determining stellar ages. With recent advances in the burgeoning field of exoplanet detection, reliable host star ages will be more important than ever in order to attain a rigorous understanding of planetary formation and evolution. The contribution of this work to the domain of stellar chronology for solar-type stars is two-fold: increased precision in relative age-dating by augmenting the cluster data used as age calibrators, and a novel statistical age-dating approach whereby all known stellar properties are used in unison to determine a most likely stellar age. By including additional rich open clusters for which their relative ages in comparison with other clusters are well constrained, the precision of an estimated age can be improved. In addition, by employing an innovative statistical approach in concert with the distributions of the newly added and well-studied clusters, age-dating precision can be further refined. The efficacy and applicability of this advanced age-dating procedure is demonstrated by the target selection strategy for the Gemini Planet Imager. The unified age-dating scheme is combined with the large scale spectroscopic survey to create a comprehensive list of nearby, young, solar-type stars with reliable ages as the optimum targets for the direct imaging of exoplanets.