Author ORCID Identifier

https://orcid.org/0000-0002-3311-4085

Date of Award

8-10-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Advisor

Fabien R. Baron

Second Advisor

Stuart M. Jefferies

Third Advisor

Russel White

Fourth Advisor

Gerard van Belle

Abstract

High-resolution interferometric imaging is currently the most accurate technique to image the surfaces of stars. However, optical interferometric imaging is a difficult ill-posed problem where a handful of imaging codes are able to find a solution, especially in three dimensions. We present the development of a 3D interferometric image reconstruction code, which has the capabilities to model/image the surfaces of spherical, spheroid, and Roche objects. We apply our open source code to two different data sets. The first application is for the RS CVn variable, lambda Andromedae, using archival interferometric data from the CHARA Array obtained with the MIRC instrument at two different epochs to better understand the evolution of its surface features. We are able to obtain precise measurements of its physical parameters as well as images of its surface detailing large-scale magnetic spots. Our results show that the reconstructed images of lambda Andromedae have starspots that seem to favor certain northern latitudes with very minimal to no spot activity in the southern latitudes, indicative of a non-solar dynamo. The second application is for the rapidly rotating star, Alderamin, with data obtained from CHARA with the MIRC-X instrument to continue unveiling the complexities of the internal mechanisms of rapid rotation. We present our preliminary imaging results, which show a slightly lower angular velocity compared to previous works along with a weak limb-darkening. These new results provide a quantitative result for limb-darkening for rapid rotators, which has not been explored before. In addition to our rapid rotator imaging, we integrate new a gravity darkening law, which will serve as improved initial parameter estimates for future imaging campaigns. To complement future imaging campaigns, we present preliminary results for a novel multi-beam atmospheric turbulence simulator that can be used to study free-space beam propagation. This latter project will serve as the groundwork for having movable telescopes at interferometric arrays, such as the CHARA Array, which will provide more (u,v) coverage and ultimately improve the quality of interferometric imaging. We use our simulator to investigate beam combination under severe ground layer turbulence conditions.

DOI

https://doi.org/10.57709/23974834

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