2017ApJ...851...39G -
Astrophys. J., 851, 39-39 (2017/December-2)
Gravity modes reveal the internal rotation of a post-mass-transfer Gamma Doradus/Delta Scuti hybrid pulsator in Kepler eclipsing binary KIC 9592855.
GUO Z., GIES D.R. and MATSON R.A.
Abstract (from CDS):
We report the discovery of a post-mass-transfer Gamma Doradus/Delta Scuti hybrid pulsator in the eclipsing binary KIC 9592855. This binary has a circular orbit, an orbital period of 1.2 days, and contains two stars of almost identical masses (M1=1.72 M☉,M2=1.71 M☉). However, the cooler secondary star is more evolved (R2=1.96 R☉), while the hotter primary is still on the zero-age-main-sequence (R1=1.53 R☉). Coeval models from single-star evolution cannot explain the observed masses and radii, and binary evolution with mass-transfer needs to be invoked. After subtracting the binary light curve, the Fourier spectrum shows low-order pressure-mode pulsations, and more dominantly, a cluster of low-frequency gravity modes at about 2 day–1. These g-modes are nearly equally spaced in period, and the period spacing pattern has a negative slope. We identify these g-modes as prograde dipole modes and find that they stem from the secondary star. The frequency range of unstable p-modes also agrees with that of the secondary. We derive the internal rotation rate of the convective core and the asymptotic period spacing from the observed g-modes. The resulting values suggest that the core and envelope rotate nearly uniformly, i.e., their rotation rates are both similar to the orbital frequency of this synchronized binary.
Abstract Copyright:
© 2017. The American Astronomical Society. All rights reserved.
Journal keyword(s):
asteroseismology - binaries: eclipsing - stars: evolution - stars: interiors - stars: oscillations - stars: variables: delta Scuti - stars: variables: delta Scuti
Simbad objects:
17
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