Kepler-1972 transit timing variations

However, TTVs can also prevent the detection of small planets in transit surveys, or bias the recovered planetary and transit parameters. Here we show that Kepler-1972 c, initially the "not transit-like" false positive KOI-3184.02, is an Earth-sized planet whose orbit is perturbed by Kepler-1972 b (initially KOI-3184.01).

The pair is locked in a 3:2 mean- motion resonance, each planet displaying TTVs of more than 6h of amplitude over the duration of the Kepler mission. The two planets have similar masses m_b_/m_c_=0.956_-0.051_^+0.056^ and radii R_b_=0.802_-0.041_^+0.042^R_{Earth}_, R_c_=0.868_-0.050_^+0.051^R_{Earth}_, and the whole system, including the inner candidate KOI-3184.03, appears to be coplanar. Despite the faintness of the signals (signal-to-noise ratio (S/N) of 1.35 for each transit of Kepler-1972 b and 1.10 for Kepler-1972 c), we recovered the transits of the planets using the RIVERS method, which is based on recognition of the tracks of planets in river diagrams using machine learning, and a photo-dynamic fit of the light curve.