Radial velocities of HD215152

This discovery is based on 373 high quality radial velocity measurements taken by HARPS over thirteen years. Given the low masses of the planets, the S/N is not sufficient to constrain the planets eccentricities.

However, a preliminary dynamical analysis suggests that eccentricities should be typically lower than about 0.03 for the system to remain stable. With two pairs of planets with a period ratio smaller than 1.5, with short orbital periods, small masses, and small eccentricities, HD215152 is similar to the very compact multi-planet systems found by Kepler, and very rare in RV surveys. This discovery proves that those systems are reachable with the RV technique, however they require a huge amount of observations to be characterized.