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A reanalysis of the composition of K2-106b, an ultra-short period super-Mercury candidate

Presentation #102.197 in the session Poster Session.

Published onJun 20, 2022
A reanalysis of the composition of K2-106b, an ultra-short period super-Mercury candidate

Super-Mercuries are a class of exoplanets with radii less than ~1.5 RE with bulk densities and core-mass fractions (CMFs) that are higher than expected assuming that their composition reflects the photospheric abundances of their host star. The study of super-Mercuries sheds light on the composition of low-mass, terrestrial exoplanets as well as on the mechanisms that lead to the formation of iron-rich planets. However, only a few exoplanets have been confirmed as super-Mercuries, in part because of the challenges of obtaining the precise stellar and planetary parameters required to confirm them. We perform a reanalysis of the K2-106 system, which contains an ultra-short period, super-Mercury candidate with a density roughly twice that of Earth. We globally model extant photometry and radial velocity of the system and derive a planetary mass and radius that implies a considerably lower density than previously reported. Using a statistical framework, we compared the planet’s CMF as expected from the planet’s density and the CMF as expected from the host star. Our analysis suggests that, although K2-106b indeed has a relatively high density and CMF, given the parameter uncertainties, it is not possible to robustly conclude that it is a true Super-Mercury. Our methodology can be further applied to other systems in order to shed light on the interior and composition of small planets.

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