Asteroseismic inference on a population scale: From detection to internal properties

Hatt, Emily (2024). Asteroseismic inference on a population scale: From detection to internal properties. University of Birmingham. Ph.D.

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Abstract

Stars give off light which enables the evolution of intelligent life and gives it access to information about the universe it inhabits. Despite their importance, our understanding of the inner workings of these objects is still far from complete. This thesis is dedicated to the only probe capable of providing observational information about the deep interiors of stars, asteroseismology, the study of stellar oscillations. In the following I will study the solar-like oscillator, in which sound waves are excited and subsequently trapped, manifesting in pulsations. Alongside probing the conditions in the interior of a star, observations of these oscillations provide accurate and precise constraints on fundamental stellar parameters. Asteroseismic measurements of stellar masses, radii, and ages have advanced several fields outside of stellar astrophysics, including exoplanet research and the study of the history of the Milky Way. In this thesis, I will cover a range of asteroseismic analyses, from detecting the presence of solar-like oscillations to exploiting the pulsations to measure the properties of stellar cores.
After a brief introduction to stellar evolution and an overview of the basics of asteroseismic analysis, I will present three works. The first introduces an automated pipeline we designed to detect solar-like oscillations using measurements of stellar flux as a function of time. This pipeline is then applied to data collected by NASA’s TESS mission for over 200,000 stars, generating a catalogue of thousands of solar-like oscillators. The next work looks to the future of asteroseismology, presenting predictions for the proposed HAYDN space telescope. The mission would exploit solar-like oscillators in stellar clusters to answer some of the most pressing open questions in stellar astrophysics and the history of the Milky Way. Two features of stellar evolution that could be investigated are core rotation and core magnetic fields. I comment on the potential for using HAYDN to make asteroseismic inferences on these properties and evaluate potential detection biases. Finally, I present the first large catalogue of asteroseismic probes of core rotation and magnetism in real stars observed by Kepler. In this catalogue I identify a bimodality in the distribution of core rotation rates which has not yet been replicated by stellar models and has implications for our understanding of angular momentum transport in stars.
Asteroseismology has provided us with tools to investigate stars in unprecedented levels of detail. To fully exploit this information to better our understanding of stellar evolution, we require larger and more complete catalogues of seismic parameters. In this thesis I build upon this, both introducing new methods to assist asteroseismic analysis in large datasets and reporting thousands of new measurements from the most fundamental detections to probes of the deep interiors of stars. The future of the field will see missions like ESA’s PLATO providing even more data amenable to asteroseismic analysis, making the tools and results detailed here a crucial chapter in the ongoing asteroseismic story.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):