A deeper view of the CoRoT-9 planetary system: A small non-zero eccentricity for CoRoT-9b likely generated by planet-planet scattering

BONOMO, A.S.; BOUCHY, F.; AIGRAIN, S.; CABRERA, J.; DEEG, H.J.; ERIKSON, A.; GUENTHER, E.; HÉBRARD, G.; IZIDORO, A.; LECAVELIER DES ETANGS, A.; OLLIVIER, M.; ALMENARA, J.-M.; ROUAN, D.; CSIZMADIA, SZ.; RAYMOND, S.N.; DELEUIL, M.; BORDÉ, P.; FRIDLUND, M.; ALONSO, R.; GUILLOT, T.; DAMIANI, C.; LOVIS, C.; DÍAZ, R.F.; PÄTZOLD, M.; GANDOLFI, D.; SANTERNE, A.; HATZES, A.; MOUTOU, C.; RAUER, H.; SCHNEIDER, J.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2017 vol. 603

0004-6361

CoRoT-9b is one of the rare long-period (P = 95.3 days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already published measurements we redetermine the CoRoT-9 system parameters and find good agreement with the published values. We uncover a higher significance for the small but non-zero eccentricity of CoRoT-9b () and find no evidence for additional planets in the system. We use simulations of planet-planet scattering to show that the eccentricity of CoRoT-9b may have been generated by an instability in which a ∼ 50 M⊕ planet was ejected from the system. This scattering would not have produced a spin-orbit misalignment, so we predict that the CoRoT-9b orbit should lie within a few degrees of the initial plane of the protoplanetary disk. As a consequence, any significant stellar obliquity would indicate that the disk was primordially tilted.