Dissertations, Theses, and Capstone Projects

Date of Degree

9-2024

Document Type

Master's Thesis

Degree Name

Master of Science

Program

Astrophysics

Advisor

Keaton Bell

Subject Categories

Numerical Analysis and Scientific Computing | Stars, Interstellar Medium and the Galaxy

Keywords

Asteroseismology, Stellar Pulsation, Stars, Binary Systems, Spherical Harmonics

Abstract

The era of the Kepler/K2 and TESS space-telescope missions has inundated the astrophysics community with photometric data for millions of stars with continuous observation and very high cadence. This data confirms that nearly every observed stellar source exhibits an oscillating luminosity, with stellar pulsation being the driving mechanism behind a large fraction of the cause. The result has been an explosion in the field of asteroseismology, where the recorded luminosity variations, or "light curves", of pulsating stars to probe their interior structures. By modeling observed light curves, we can constrain values of the physical stellar parameters producing them. The brightness variation patterns of the pulsating stellar surface can be accurately modeled as a sum of integrated surface fluxes of oscillating spherical harmonic modes. We can reconstruct the stellar surface geometry and also recreate observational light curves by conglomerating the proper spherical harmonic modes with appropriate pulsation parameter values of amplitude, frequency, and phase. As these pulsation parameters are often observable physical quantities determined from collected data, the major challenge lies within matching the observed parameters to the correct spherical harmonic mode producing them. Thus, it is prudent to construct tools to identify the spherical harmonic patterns underlying stellar pulsation observations in an efficient and accurate way. This is the motivation in building the Python package: PULSEY. This stellar pulsation modeling package is capable of simulating spherical harmonic mode pulsations, producing light curves, simulating pulsators in Keplerian orbits as observed in binary star systems, and deconstructing degeneracies of spherical harmonic pulsation modes in eclipsing binary systems via the eclipse-mapping method. PULSEY also confidently recovers known stellar parameters from input simulated light curve data, establishing its accuracy as an asteroseismological tool. Additionally, the package also serves as a science visualization tool in allowing scientists, and general audiences alike, to visualize stellar surface patterns and symmetries in an unprecedented way. PULSEY is an open-source software and is available to download for public use.

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