Author ORCID Identifier

https://orcid.org/0000-0002-2600-7513

Date of Award

Spring 4-24-2024

Document Type

Thesis (Ph.D.)

Department or Program

Physics and Astronomy

First Advisor

Brian Chaboyer

Second Advisor

Elisabeth Newton

Third Advisor

Aaron Dotter

Abstract

Low mass stars account for approximately 70 percent of the stellar populations (Conroy & Van Dokkum, 2012); yet, due to their small sizes and cool temperatures they account for only a small fraction of the galaxies luminosity function (Laughlin et al., 1997). Moreover, due to the lack of laboratory conditions available to astronomy and astrophysics low mass stars can provide a rare controlled environment for calibrations of numerical models. Consequently, across multiple domains there has been significant interest in these key astronomical objects. In this thesis I present three projects which have further revealed properties of low mass stars and pushed the extent where these low mass stars may be used as laboratories. Firstly, I present chemically self consistent stellar evolutionary models of the globular clusters NGC 2808. Due to the age of this cluster, these models are dominated by low mass stars. We find that chemical consistency between a stars structural and atmospheric models makes only a trivial difference in model predictions. Secondly, I present a detailed investigation into the Gaia M Dwarf Gap (the Jao Gap) looking at how the Jao Gap’s theoretical location is effected by high temperature radiative opacity source and how the physics which drives the Jao Gap’s formation may also drive perturbations to stellar magnetic field strength. A detailed understanding of the Jao Gap’s underlying physics may provide an important calibration point for M dwarf convective parameters. The work presented in this thesis brings the field of astronomy closer to being able to use those calibrations. Finally, this thesis investigates the relation between the red giant branch bump (RGBB) in both NGC 2808 across multiple populations and across multiple opacity sources. Similar to the Jao Gap, the RGBB provides a calibration point for convective parameters in stars on the red giant branch. We find that the helium enriched population in NGC 2808 does not show a detectable RGBB, validating previous theoretical studies of the RGBB which did not consider multiple populations in their modeling.

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