Volume 661, May 2022
|Number of page(s)||8|
|Section||Planets and planetary systems|
|Published online||31 May 2022|
Alleviating the transit timing variation bias in transit surveys
II. RIVERS: Twin resonant Earth-sized planets around Kepler-1972 recovered from a Kepler false positive★
Observatoire de Genève, Université de Genève,
Chemin Pegasi, 51,
2 School of Physics and Astronomy, Monash University, Victoria 3800, Australia
3 Distaitek, 10 rue Achille Antheaume, 95190 Fontenay-en-Parisis, France
4 Physikalisches Institut, Universität Bern, Gesellschaftsstr. 6, 3012 Bern, Switzerland
Accepted: 19 January 2022
Transit timing variations (TTVs) can provide useful information for systems observed in this way, putting constraints on the masses and eccentricities of the observed planets, and in some cases even revealing the existence of non-transiting companions. 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 mb/mc = 0.956−0.051+0.056 and radii Rb = 0.802−0.041+0.042REarth, Rc = 0.868−0.050+0.051REarth, 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. Recovering the correct ephemerides of the planets is essential to obtaining a complete picture of the observed planetary systems. In particular, we show that in Kepler-1972, not taking into account planet-planet interactions yields an error of ~30% on the radii of planets b and c, in addition to generating in-transit scatter, which is why KOI3184.02 was mistaken for a false positive. Alleviating this bias is essential for an unbiased view of Kepler systems, some of the TESS stars, and the upcoming PLATO mission.
Key words: planets and satellites: dynamical evolution and stability / planets and satellites: terrestrial planets / techniques: photometric / methods: numerical
The time of transits of the detected planets is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/661/A141
© ESO 2022
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