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We measure the rotation periods of 19 stars in the {it Kepler} transiting planetary systems, $P_{rm rot, astero}$ from asteroseismology and $P_{rm rot, phot}$ from photometric variation of their lightcurve. Two stars exhibit two clear peaks in the Lomb-Scargle periodogram, neither of which agrees with the seismic rotation period. Other four systems do not show any clear peak, whose stellar rotation period is impossible to estimate reliably from the photometric variation; their stellar equators may be significantly inclined with respect to the planetary orbital plane. For the remaining 13 systems, $P_{rm rot, astero}$ and $P_{rm rot, phot}$ agree within 30%. Interestingly, three out of the 13 systems are in the spin-orbit resonant state in which $P_{rm orb, b}/P_{rm rot, astero} approx 1$ with $P_{rm orb, b}$ being the orbital period of the inner-most planet of each system. The corresponding chance probability is ($0.2$-$4.7$) % based on the photometric rotation period data for 464 {it Kepler} transiting planetary systems. While further analysis of stars with reliable rotation periods is required to examine the statistical significance, the spin-orbit resonance between the star and planets, if confirmed, have important implications for the star-planet tidal interaction, in addition to the origin of the spin-orbit (mis-)alignment of transiting planetary systems.
Revealing the mechanisms shaping the architecture of planetary systems is crucial for our understanding of their formation and evolution. In this context, it has been recently proposed that stellar clustering might be the key in shaping the orbital a
We present a test for spin-orbit alignment for the host stars of 25 candidate planetary systems detected by the {it Kepler} spacecraft. The inclination angle of each stars rotation axis was estimated from its rotation period, rotational line broadeni
We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the
The discovery of multiple transiting planetary systems offers new possibilities for characterising exoplanets and understanding their formation. The Kepler-9 system contains two Saturn-mass planets, Kepler-9b and 9c. Using evolution models of gas gia
We present spectroscopic measurements of the Rossiter-McLaughlin effect for the planet b of Kepler-9 multi-transiting planet system. The resulting sky-projected spin-orbit angle is $lambda=-13^{circ} pm 16^{circ}$, which favors an aligned system and