Cedric Ramesh

Date of Award

January 2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Space Studies

First Advisor

Tim Young

Abstract

The star α Orionis (Betelgeuse) has enjoyed increased fame and scrutiny over the past two years, largely due to a mysterious dimming event that began in November 2019. Betelgeuse’s relatively close distance combined with its somewhat substantial angular diameter allows for direct imaging of its surface (as performed by the Hubble Space Telescope, 1996) along with a host of other detailed observations. These observations grant an excellent baseline upon which to conduct a parameter study using MESA (Modules for Experiments in Stellar Astrophysics), a 1D software stellar evolution code.Even though one-dimensional stellar evolution is a mature discipline, we continue to ask new questions of stars. Certain aspects of stars are truly three-dimensional, such as convection, rotation, and magnetism. Those applications remain in the realm of research frontiers with evolving understanding and insights. However, much remains to be gained scientifically by accurate one-dimensional calculations. Parameters of interest are initial mass, mixing length alpha (α), initial metallicity (Z), Ledoux vs. Schwarzschild criteria, convective overshoot, alpha semiconvection, and prescriptions for mass loss. These parameters are thoroughly investigated over several trial simulations using MESA. Various results agree with the Dolan et al. (2016) model. Some results, such as convective overshoot and mass loss prescriptions, are improved upon over the Dolan et al. model. Other novel results, such as Ledoux vs. Schwarzschild MESA trials, are presented for review.

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