EPIC 211418729b and EPIC 211442297b: 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 $10^8$ erg s$^{-1}$ 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 ${it K2}$ photometry. EPIC 211418729b has a mass of $1.85^{+0.23}_{-0.22} M_J$, a radius of $0.942^{+0.032}_{-0.020} R_J$, and an orbital period of 11.4 days. EPIC 211442297b has a mass of $0.84^{+0.18}_{-0.20} M_J$, a radius of $1.115^{+0.057}_{-0.061} R_J$, 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 10$^8$ erg s$^{-1}$ cm$^{-2}$, suggesting that for warm Jupiters the stellar irradiation does not play a significant role in determining the planet radius. We also report our identification of another ${it K2}$ transiting warm Jupiter candidate, EPIC 212504617, as a false positive.