We searched for extrasolar planets around pulsating stars by examining
Kepler data for transit-like events hidden in the intrinsic variability.
All short-cadence observations for targets with 6000 <
Teff < 8500 K were visually inspected for transit-like
events following the removal of pulsational signals by sinusoidal fits.
Clear transit-like events were detected in KIC 5613330 and KIC 8197761.
KIC 5613330 is a confirmed exoplanet host (Kepler-635b), where the
transit period determined here is consistent with the literature value.
KIC 8197761 is a γ Doradus-δ Scuti star exhibiting
eclipses/transits occurring every 9.868 6667(27) d, having durations of
8.37 h and causing brightness drops Δ F/F = 0.006 29(29). The
star's pulsation spectrum contains several mode doublets and triplets,
identified as l = 1, with a mean spacing of 0.001 659(15) d-1
, implying an internal rotation period of 301 ± 3 d. Trials to
calculate the size of the light travel time effect (LTTE) from the
pulsations to constrain the companion's mass ended inconclusive. Finding
planets around γ Doradus stars from the pulsational LTTE,
therefore, is concluded to be unrealistic. Spectroscopic monitoring of
KIC 8197761 revealed sinusoidal radial velocity variations with a
semi-amplitude of 19.75 ± 0.32 km s-1, while
individual spectra present rotational broadening consistent with vsin i
= 9 ± 1 km s-1. This suggests that the stellar surface
rotation is synchronized with the orbit, whereas the stellar core
rotates ˜30 times slower. Combining the observed radial velocity
variability with the transit photometry, constrains the companion's mass
to be ≈0.28 M⊙, ruling out an exoplanet hypothesis.