Search for exoplanets around pulsating stars of A--F type in Kepler Short Cadence data and the case of KIC 8197761

Abstract

We searched for extrasolar planets around pulsating stars by examining $\text{Kepler}$ data for transit-like events hidden in the intrinsic variability. All Short Cadence observations for targets with 6000 K $<T_{\mathrm{eff}}<$ 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 $\gamma$ Doradus - $\delta$ Scuti star exhibiting eclipses/transits occurring every 9.8686667(27) d, having durations of 8.37 h, and causing brightness drops $\frac{\Delta F}{F}=0.00629(29)$. The star's pulsation spectrum contains several mode doublets and triplets, identified as $l=1$, with a mean spacing of 0.001659(15) c/d, implying an internal rotation period of $301\pm 3$ 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 $\gamma$ 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 $19.75\pm 0.32$ km/s, while individual spectra present rotational broadening consistent with $v\sin i=9\pm 1$ km/s. This suggests that the stellar surface rotation is synchronized with the orbit, whereas the stellar core rotates $\sim$30 times slower. Combining the observed radial velocity variability with the transit photometry, constrains the companion's mass to be $\approx 0.28$ M${}_{\odot }$, ruling out an exoplanet hypothesis.

12 pages, 9 figures, accepted for publication in MNRAS

References in corpus (10)

• Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars
• An ancient extrasolar system with five sub-Earth-size planets
• Asteroseismic measurement of slow, nearly-uniform surface-to-core rotation in the main sequence F star KIC 9244992
• A precise asteroseismic age and radius for the evolved Sun-like star KIC 11026764
• A heuristic derivation of the uncertainty of the frequency determination in time series data
• Reevaluating the Mass-Radius Relation for Low-Mass, Main Sequence Stars
• CASSIS: The Cornell Atlas of Spitzer/Infrared Spectrograph Sources. II. High-resolution observations
• Finding binaries among Kepler pulsating stars from phase modulation of their pulsations
• Rejecting Astrophysical False Positives from the TrES Transiting Planet Survey: The Example of GSC 03885-00829
• A planet in an 840-d orbit around a Kepler main-sequence A star found from phase modulation of its pulsations

Cited by in corpus (15)

• Slowing the Spins of Stellar Cores
• The interior angular momentum of core hydrogen burning stars from gravity-mode oscillations
• The effect of tides on near-core rotation: analysis of 35 Kepler $\gamma$ Doradus stars in eclipsing and spectroscopic binaries
• A transit survey to search for planets around hot subdwarfs: I. methods and performance tests on light curves from Kepler, K2, TESS, and CHEOPS
• A comparison of the dynamical and model-derived parameters of the pulsating eclipsing binary KIC9850387
• Transiting Planets near the Snow Line from Kepler. I. Catalog
• Tango of celestial dancers: A sample of detached eclipsing binary systems containing g-mode pulsating components. A case study of KIC9850387
• Inverse Tides in Pulsating Binary Stars
• The traditional approximation of rotation for rapidly rotating stars and planets. II. Deformation and differential rotation
• Four bright eclipsing binaries with gamma Doradus pulsating components: CM Lac, MZ Lac, RX Dra and V2077 Cyg
• Constraining the near-core rotation of the gamma Doradus star 43 Cygni using BRITE-Constellation data
• Asteroseismology of two Kepler detached eclipsing binaries
• Mode coupling coefficients between the convective core and radiative envelope of $\gamma$Doradus and slowly pulsating B stars
• A search for transits among the δ Scuti variables in Kepler
• Resonance locking and tidal evolution in rotating γ-Doradus binaries