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 ( M _ { 1 } = 1.72 M _ { \odot } ,M _ { 2 } = 1.71 M _ { \odot } ) .
However , the cooler secondary star is more evolved ( R _ { 2 } = 1.96 R _ { \odot } ) while the hotter primary is still on the zero-age-main-sequence ( R _ { 1 } = 1.53 R _ { \odot } ) .
Coeval models from single star evolution can not 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 .