We report the discovery of a transiting , R _ { p } = 4.347 \pm 0.099 R _ { \oplus } , circumbinary planet ( CBP ) orbiting the Kepler K + M Eclipsing Binary ( EB ) system KIC 12351927 ( Kepler-413 ) every \sim 66 days on an eccentric orbit with a _ { p } = 0.355 \pm 0.002 AU , e _ { p } = 0.118 \pm 0.002 .
The two stars , with M _ { A } = 0.820 \pm 0.015 M _ { \odot } ,R _ { A } = 0.776 \pm 0.009 R _ { \odot } and M _ { B } = 0.542 \pm 0.008 M _ { \odot } ,R _ { B } = 0.484 \pm 0.024 R _ { \odot } respectively revolve around each other every 10.11615 \pm 0.00001 days on a nearly circular ( e _ { EB } = 0.037 \pm 0.002 ) orbit .
The orbital plane of the EB is slightly inclined to the line of sight ( i _ { EB } = 87.33 \pm 0.06 \arcdeg ) while that of the planet is inclined by \sim 2.5 \arcdeg to the binary plane at the reference epoch .
Orbital precession with a period of \sim 11 years causes the inclination of the latter to the sky plane to continuously change .
As a result , the planet often fails to transit the primary star at inferior conjunction , causing stretches of hundreds of days with no transits ( corresponding to multiple planetary orbital periods ) .
We predict that the next transit will not occur until 2020 .
The orbital configuration of the system places the planet slightly closer to its host stars than the inner edge of the extended habitable zone .
Additionally , the orbital configuration of the system is such that the CBP may experience Cassini-States dynamics under the influence of the EB , in which the planet ’ s obliquity precesses with a rate comparable to its orbital precession .
Depending on the angular precession frequency of the CBP , it could potentially undergo obliquity fluctuations of dozens of degrees ( and complex seasonal cycles ) on precession timescales .