K2-114b and K2-115b:two transiting warm Jupiters

We report the first results from a search for transiting warm Jupiter exoplanets—gas giant planets receiving stellar irradiation below about 108 erg−1 cm−2, equivalent to orbital periods beyond about 10 days around Sun-like stars. We have discovered two transiting warm Jupiter exoplanets initially identified as transiting candidates in K2 photometry. K2-114b has a mass of 1.85^(+0.23)_(-0.22) MJ, a radius of 0.942^(+0.032)_(-0.020) RJ, and an orbital period of 11.4 days. K2-115b has a mass of 0.84^(+0.18)_(-0.20) MJ, a radius of 1.115^(+0.057)_(-0.061) RJ, and an orbital period of 20.3 days. Both planets are among the longest-period transiting gas giant planets with a measured mass, and they are orbiting relatively old host stars. Both planets are not inflated, as their radii are consistent with theoretical expectations. Their position in the planet radius–stellar irradiation diagram is consistent with the scenario where the radius–irradiation correlation levels off below about 108 erg s−1 cm−2, suggesting that for warm Jupiters stellar irradiation does not play a significant role in determining the planet radius. We also report our identification of another K2 transiting warm Jupiter candidate, EPIC 212504617, as a false positive.