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A survey for pulsations in A-type stars using SuperWASP

A survey for pulsations in A-type stars using SuperWASP Thumbnail


Abstract

A survey of A-type stars is conducted with the SuperWASP archive in the search for pulsationally variable stars. Over 1.5 million stars are selected based on their (J - H) colour. Periodograms are calculated for light curves which have been extracted from the archive and cleaned of spurious points. Peaks which have amplitudes greater than 0.5 millimagnitude are identi?ed in the periodograms. In total, 202 656 stars are identi?ed to show variability in the range 5 - 300 d-1.

Spectroscopic follow-up was obtained for 38 stars which showed high-frequency pulsations between 60 and 235 d-1, and a further object with variability at 636 d-1. In this sample, 13 were identi?ed to be normal A-type d Sct stars, 14 to be pulsating metallic-lined Am stars, 11 to be rapidly oscillating Ap (roAp) stars, and one to be a subdwarf B variable star. The spectra were used not only to classify the stars, but to determine an e?ective temperature through Balmer line ?tting.

Hybrid stars have been identi?ed in this study, which show pulsations in both the high- and low-overtone domains; an observation not predicted by theory. These stars are prime targets to perform follow-up observations, as a con?rmed detection of this phenomenon will have signi?cant impact on the theory of pulsations in A-type stars.

The detected number of roAp stars has expanded the known number of this pulsator class by 22 per cent. Within these results both the hottest and coolest roAp star have been identi?ed. Further to this, one object, KIC 7582608, was observed by the Kepler telescope for 4 yr, enabling a detailed frequency analysis. This analysis has identi?ed signi?cant frequency variations in this star, leading to the hypothesis that this is the ?rst close binary star of its type.

The observational results presented in this thesis are able to present new challenges to the theory of pulsations in A-type stars, with potentially having the e?ect of further delaying the full understanding of ‘so simple a thing as a star’.

Publicly Available Date Mar 29, 2024

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