Kavli Affiliate: Andrew Vanderburg
| First 5 Authors: Chantanelle Nava, Mercedes López-Morales, Annelies Mortier, Li Zeng, Helen A. C. Giles
| Summary:
We present mass and radius measurements of K2-79b and K2-222b, two transiting
exoplanets orbiting active G-type stars. Their respective 10.99d and 15.39d
orbital periods fall near periods of signals induced by stellar magnetic
activity. The two signals might therefore interfere and lead to an inaccurate
estimate of exoplanet mass. We present a method to mitigate these effects when
radial velocity and activity indicator observations are available over multiple
observing seasons and the orbital period of the exoplanet is known. We perform
correlation and periodogram analyses on sub-sets composed of each target’s two
observing seasons, in addition to the full data sets. For both targets, these
analyses reveal an optimal season with little to no interference at the orbital
period of the known exoplanet. We make a confident mass detection of each
exoplanet by confirming agreement between fits to the full radial velocity set
and the optimal season. For K2-79b, we measure a mass of 11.8 $pm$ 3.6
$M_{Earth}$ and a radius of 4.09 $pm$ 0.17 $R_{Earth}$. For K2-222b, we
measure a mass of 8.0 $pm$ 1.8 $M_{Earth}$ and a radius of 2.35 $pm$ 0.08
$R_{Earth}$. According to model predictions, K2-79b is a highly irradiated
Uranus-analog and K2-222b hosts significant amounts of water ice. We also
present an RV solution for a candidate second companion orbiting K2-222 at
147.5d.
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