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Pulsating A-type stars seen with Kepler

Simon J. Murphy
Jeremiah Horrocks Institute, University of Central Lancashire

The Kepler data, with their regular sampling, very high duty cycle, micro-magnitude precision and long observational time span represent a new era in asteroseismic study. Understanding the particular properties of these data is of paramount importance in fully utilising the data. One such property on which I focus is the Nyquist frequency. I show that, for the long, continuous datasets that Kepler generally offers, the barycentric corrections made to the data break the regular sampling of the data. This periodic modulation causes Nyquist aliases to be split into multiplets, while real peaks remain as singlets. Real frequencies and Nyquist aliases can therefore be distinguished.
Kepler also observes an incredible number of targets simultaneously. It is then likely that some of the targets observed will be caught in a rapid evolutionary phase. KIC 3429637 may be one such target, where I show the star has two mutually unlikely properties - chemical peculiarity and pulsation. That the chemical peculiarities are weak and the pulsational amplitudes growing suggests the star is leaving a stable, chemically-peculiar state and entering a chemically-normal state that is unstable to pulsation.

2012 November 14, 13:30

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