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Title: Observational constraints on pre-main sequence stellar evolution from time-series analysis of open cluster stars
Author: Irwin, J. M.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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Observational constraints on evolutionary models of low-mass stars (≲ 1.0 M) are presently extremely scarce on the pre-main sequence. Recent observational evidence has indicated substantial discrepancies between the predictions of these models and observations made in binary star systems, where the masses can be measured dynamically. It is clear that in order to resolve these issues, a larger sample of precise measurements will be needed to anchor the theory. This work pursues two avenues to do this, using time-series photometric measurements in young open clusters (ages 1 – 200 Myr) obtained as part of the Monitor project, a large-scale survey using 2 – 4 m class telescopes. Stellar rotation periods are readily measured using photometry alone, and yet probe directly a fundamental stellar property: the angular velocity. These measurements place direct constraints on models of rotational evolution, had hence on the stellar models themselves. By examining rotation periods in six of the Monitor open clusters, I show that simple rotational evolution models can partially describe the data, with rapid rotators better-described by a model assuming rotation as a solid body, and slower rotators by a model including differential rotation between the radiative core and convective envelope in stars with masses ≳ 0.4 M, but that more theoretical work is clearly needed to resolve discrepancies between the models and the data. Eclipsing binary systems provide some of the most precise and accurate determination of stellar masses and radii available, from combined analysis of radial velocity and light curves. Searching for these systems is one of the primary science goals of Monitor. Dynamical solutions are presented for four of these systems, and two found to be on the pre-main sequence are compared to the predictions of the models, finding reasonable agreement in the mass-radius plane, but that there may be significant discrepancies in the effective temperatures, as found by several other authors.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available