Two temperate sub-Neptunes transiting the star EPIC 212737443

Abstract

We report the validation of a new planetary system around the K3 star EPIC 212737443 using a combination of K2 photometry, follow-up high resolution imaging and spectroscopy. The system consists of two sub-Neptune sized transiting planets with radii of 2.6R?, and 2.7R?, with orbital periods of 13.6 days and 65.5 days, equilibrium temperatures of 536 K and 316 K respectively. In the context of validated K2 systems, the outer planet has the longest precisely measured orbital period, as well as the lowest equilibrium temperature for a planet orbiting a star of spectral type earlier than M. The two planets in this system have a mutual Hill radius of ?RH = 36, larger than most other known transiting multi-planet systems, suggesting the existence of another (possibly non-transiting) planet, or that the system is not maximally packed.