Investigating the A-Type Stars Using Kepler Data
PhD Thesis
Title | Investigating the A-Type Stars Using Kepler Data |
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Type | PhD Thesis |
Authors | |
Author | Murphy, Simon J. |
Supervisor | Kurtz, Don |
Institution of Origin | University of Central Lancashire |
Qualification Name | Doctor of Philosophy |
Number of Pages | 292 |
Year | 2013 |
Publisher | University of Central Lancashire |
Abstract | Rotation is a key physical process operating in the A stars. We present a method by which rotation periods might be measured with Fourier transforms of Kepler data, potentially removing the requirement of spectroscopic observations to acquire similar information. Angular rotational velocities reach their maximum at about A5, but slowly rotating A stars are also seen and these tend to be chemically peculiar. For Ap stars, rotational braking is understood, but too few progenitors are observed. A review of a rare class of stars, the `sn' stars, leads us to suggest these may contribute to the `missing' Ap progenitors. For Am stars, we find the tidal braking mechanisms proposed in the literature induce mixing that is incompatible with observed abundance anomalies. At the other end of the scale are the λ Boo stars, whose rotation velocities are above average. The two main theories for the origin of their metal underabundances are discussed and it is suggested that both of them imply the λ Boo stars contain a high fraction of pulsators -- a suggestion that is backed up by observations in the literature. Many λ Boo stars also have circumstellar material, suggesting they are potential planet hosts. This, and the use of asteroseismology to study their interiors, are two excellent reasons to adopt them as prime targets for detailed investigation with Kepler. |
Keywords | asteroseismology, methods: data analysis, stars: oscillations, stars: variables: delta Scuti, stars: variables: general, stars: chemically peculiar, stars: rotation |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Byline Affiliations | University of Central Lancashire, United Kingdom |
https://research.usq.edu.au/item/q739w/investigating-the-a-type-stars-using-kepler-data
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