* Astronomy

Title: One of the closest planet pairs to the 3:2 Mean Motion Resonance, confirmed with K2 observations and Transit Timing Variations: EPIC201505350
Author: David J. Armstrong, Dimitri Veras, Susana C. C. Barros, Olivier Demangeon, James McCormac, Hugh P. Osborn, Jorge Lillo-Box, Alexandre Santerne, Maria Tsantaki, José-Manuel Almenara, David Barrado, Isabelle Boisse, Aldo S. Bonomo, François Bouchy, David J. A. Brown, Giovanni Bruno, Javiera Rey Cerda, Bastien Courcol, Magali Deleuil, Rodrigo F. Díaz, Amanda P. Doyle, Guillaume Hébrard, James Kirk, Kristine W. F. Lam, Don L. Pollacco, Arvind Rajpurohit, Jessica Spake, Simon R. Walker

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 Earth radii), 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 386 Earth masses.

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