We report the discovery of EPIC 201498078b , which was first identified as a planetary candidate from Kepler K2 photometry of Campaign 14 , and whose planetary nature and orbital parameters were then confirmed with precision radial velocities .
EPIC 201498078b is half as massive as Saturn ( { M _ { P } } = 0.179 \pm 0.021 { M _ { J } } ) , and has a radius of { R _ { P } } = 0.840 \pm 0.011 { R _ { J } } , which translates into a bulk density of { \rho _ { P } } = 0.37 \pm 0.05 \mathrm { g } \mathrm { cm } ^ { -3 } .
EPIC 201498078b transits its slightly evolved G-type host star ( { M } _ { \star } = 1.105 \pm 0.019 { M } _ { \odot } , { R } _ { \star } = 1.669 \pm 0.022 { R } _ { \odot } ) every 11.63364 \pm 0.00010 days and presents a significantly eccentric orbit ( e = 0.420 \pm 0.034 ) .
We estimate a relatively short circularization timescale of 1.8 Gyr for the planet , but given the advanced age of the system we expect the planet to be engulfed by its evolving host star in \sim 1 Gyr before the orbit circularizes .
The low density of the planet coupled to the brightness of the host star ( J = 9.4 ) makes this system one of the best candidates known to date in the super-Neptune regime for atmospheric characterization via transmission spectroscopy , and to further study the transition region between ice and gas giant planets .