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Debiasing the mass radius relation for low mass exoplanets characterized via transit timing

Presentation #303.02 in the session “Exoplanets and Systems: Discoveries”.

Published onOct 26, 2020
Debiasing the mass radius relation for low mass exoplanets characterized via transit timing

Transit timing variations (TTV) have enabled the characterization of masses and radii of dozens of low mass planets in multi-transiting systems, which typically have longer orbital periods and lower densities than the sample characterized via radial velocity spectroscopy (RV) due to the detection biases of both the TTV and RV methods. A debiased mass-radius relation requires the inclusion of non-detections, which has not been done in prior TTV studies, since only a small fraction of multi-transiting systems have detectable TTVs and fitting dynamical models to all measured transit times would be numerically expensive.

We address this by selecting our sample of systems purely on photometric properties (orbital periods, planet radii and transit timing precision), and not on the prior detection of TTV. This makes our sample more amenable to detailed population modeling. We identify a set of 82 candidate planets in systems where there is an expectation of either detectable TTVs or useful upper limits prior to any TTV analysis.

Following dynamical fits and using recently improved stellar parameters for these systems, we update TTV masses on 34 planets, add 28 new masses and mass upper limits to the mass-radius diagram, and identify systems where follow-up observations are likely to improve constraints on planetary masses.

Our candidate systems provide a homogeneous sample for population studies of low-mass exoplanets, from ~2 to ~200 days in orbital period. In addition, our candidate systems provide a uniform sample of low-mass exoplanet atmospheres that are candidates for transmission spectroscopy with JWST over a range of equilibrium blackbody temperatures from above ~1300K to ~400K.

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