EPIC201505350: Two Planet System with a hot Neptune and a Giant Rocky Exoplanet in a 3:2 Orbital Resonance

One of the closest planet pairs to the 3:2 Mean Motion Resonance, confirmed with K2 observations and Transit Timing Variations: EPIC201505350

Authors:

Armstrong et al

Abstract:

The K2 mission has recently begun to discover new and diverse planetary systems. In December 2014 Campaign 1 data from the mission was released, providing high-precision photometry for ~22000 objects over an 80 day timespan. We searched these data with the aim of detecting further important new objects. Our search through two separate pipelines led to the independent discovery of EPIC201505350, a two-planet system of Neptune sized objects (4.2 and 7.2 R⊕), orbiting a K dwarf extremely close to the 3:2 mean motion resonance. The two planets each show transits, sometimes simultaneously due to their proximity to resonance and alignment of conjunctions. We obtain further ground based photometry of the larger planet with the NITES telescope, demonstrating the presence of large transit timing variations (TTVs) of over an hour. These TTVs allows us to confirm the planetary nature of the system, and place a limit on the mass of the outer planet of 386M⊕.