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Issue Date: 24-Feb-2016
Authors: Giarrusso, Marina
Title: Lithium and age of pre-main sequence stars
Abstract: The expectation to date the age of low mass pre-main sequence stars from lithium has been tested by comparing the observed lithium and the predicted abundance by evolutionary models. The test, in this thesis, has been applied on a sample of binary systems whose components have a well known mass or whose mass ratio has been exactly established. The common metallicity and the coevality of the two components of a system are strong constraints to determine the age on the basis of evolutionary codes. To achieve reliable results, by an observational campaign, I have doubled the sample of stars presenting the necessary information for the analysis. Stellar parameters have been determined with the most precise and accurately tested techniques: high resolution spectroscopy along a very large wavelength range and numerical solution of the radiative transfer equation. As to the evolutionary code, I have implemented FRANEC with the very accurate reaction rates as determined with the most reliable experimental technique, the Trojan Horse Method. Since for PMS stars the agreement between observed and predicted lithium abundance can be obtained just tuning the external convective efficiency, I have computed a database of models for different values of the mixing length parameter. Age determination of stars has been carried out by adopting what is nowadays believed to be the most powerful statistical method in the field, the Bayesian analysis. I have extended in an original way this statistical method from binary system with known masses to the most common double lined spectroscopic binaries.
Appears in Collections:Area 02 - Scienze fisiche

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