FM17.5.06 — Pulsations in Binary Stars: δ Scuti/γ Doradus pulsators and Tidally Induced 'Heartbeat' Stars

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Aug 13th at 11:56 AM until 12:08 PM

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Author(s): Zhao Guo1, Douglas R. Gies1, Rachel Matson1

Institution(s): 1. Georgia State University

The recent achievements in asteroseismology thanks to the space mission CoRoT and Kepler mainly concentrate on solar-like oscillators. For δ Scuti stars, as they are generally fast rotators and their pulsations are not in the asymptotic regime, the mode identification is a very difficult task. Binary stars, especially eclipsing systems offer the opportunity to constrain the space of fundamental stellar parameters.
Firstly, we check the general pulsational properties of detached and semi-detached eclipsing binaries with δ Scuti and γ Doradus components. The relation between the orbital frequency and the pulsational frequency reveals groups in different pulsation mode. Then we show the result of KIC9851944 as a case study. The accurate masses and radii facilitate the mode identification and greatly constrain the evolution state and overshooting parameter.
Lastly, we study the ‘heartbeat’ stars: the tidally induced pulsators in eccentric binaries. Many heartbeat binaries are found to contain A or F type primary components. Spectroscopic follow-up observations suggest that these systems typically have a relatively high mass ratio. We calculate the gravitational perturbation due to the L=2 g-modes of the A/F type primary in a binary system. In the framework of linear perturbation theory, we then analyze the tidal effect from the secondary with different masses and orbital parameters. The overall frequency range of the tidally induced pulsations predicted from theory is compared with the observed frequencies of a sample of heartbeat stars retrieved from Kepler Eclipsing Binary Catalogue.
The studies above of A/F type pulsators in binaries will help to improve our understanding of stellar physics and tidal effect in binaries.