Abstract
We have studied over 1600 Am stars at a photometric precision of 1 mmag with SuperWASP photometric data. Contrary to previous belief, we find that around 200 Am stars are pulsating delta Sct and gamma Dor stars, with low amplitudes that have been missed in previous, less extensive studies. While the amplitudes are generally low, the presence of pulsation in Am stars places a strong constraint on atmospheric convection, and may require the pulsation to be laminar. While some pulsating Am stars have been previously found to be delta Sct stars, the vast majority of Am stars known to pulsate are presented in this paper. They will form the basis of future statistical studies of pulsation in the presence of atomic diffusion.
Highlights
In the region of the Hertzsprung-Russell (HR) diagram where the Cepheid instability strip extends across the main sequence, there is a complex relationship between stellar pulsation and atmospheric abundance anomalies that is not fully understood
The combination of the all-sky mmag precision of SuperWASP with the μmag precision of CoRoT and Kepler on selected stars, calls for new attempts to model the physics of the interaction of pulsation, rotation and atomic diffusion in the A stars
The pulsating Am stars are concentrated within the fundamental radial mode red and blue edges of Dupret et al (2005). This is in agreement with that found by Balona et al (2011) for Am stars within the Kepler field. These studies show that pulsating Am stars are concentrated in the cooler region of the instability strip
Summary
In the region of the Hertzsprung-Russell (HR) diagram where the Cepheid instability strip extends across the main sequence, there is a complex relationship between stellar pulsation and atmospheric abundance anomalies that is not fully understood. The Kepler Mission through KASC will model individual Am stars that are δ Sct pulsators with data of such high precision that new insight into the physics of the relationship between atomic diffusion and p mode pulsation will be obtained. More constraints on the physics of the interaction of pulsation and atomic diffusion may be found in stars that show no δ Sct p modes or γ Dor g modes at precisions of μmag Some such A stars are known in the CoRoT and Kepler data sets, but in-depth studies have not yet been made, discussions of these have yet to be published. The combination of the all-sky mmag precision of SuperWASP with the μmag precision of CoRoT and Kepler on selected stars, calls for new attempts to model the physics of the interaction of pulsation, rotation and atomic diffusion in the A stars
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