TY - JOUR
T1 - K2-79b and K2-222b
T2 - mass measurements of two small exoplanets with periods beyond 10 days that overlap with periodic magnetic activity signals
AU - Nava, Chantanelle
AU - López-Morales, Mercedes
AU - Mortier, Annelies
AU - Zeng, Li
AU - Giles, Helen A. C.
AU - Bieryla, Allyson
AU - Vanderburg, Andrew
AU - Buchhave, Lars A.
AU - Poretti, Ennio
AU - Saar, Steven H.
AU - Dumusque, Xavier
AU - Latham, David W.
AU - Charbonneau, David
AU - Damasso, Mario
AU - Bonomo, Aldo S.
AU - Lovis, Christophe
AU - Collier cameron, Andrew
AU - Eastman, Jason D.
AU - Sozzetti, Alessandro
AU - Cosentino, Rosario
AU - Pedani, Marco
AU - Pepe, Francesco
AU - Molinari, Emilio
AU - Sasselov, Dimitar
AU - Mayor, Michel
AU - Stalport, Manu
AU - Malavolta, Luca
AU - Rice, Ken
AU - Watson, Christopher A.
AU - Martinez fiorenzano, A. F.
AU - Di fabrizio, Luca
PY - 2022/2
Y1 - 2022/2
N2 - We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars observed with HARPS-N and K2. Their respective 10.99 day and 15.39 day 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 (RV) 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 subsets 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 RV set and the optimal season. For K2-79b, we measure a mass of 11.8 ± 3.6 M⊕ and a radius of 4.09 ± 0.17 R⊕. For K2-222b, we measure a mass of 8.0 ± 1.8 M⊕ and a radius of 2.35 ± 0.08 R⊕. According to model predictions, K2-79b is a highly irradiated Uranus analog and K2-222b hosts significant amounts of water ice. We also present a RV solution for a candidate second companion orbiting K2-222 at 147.5 days.
AB - We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars observed with HARPS-N and K2. Their respective 10.99 day and 15.39 day 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 (RV) 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 subsets 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 RV set and the optimal season. For K2-79b, we measure a mass of 11.8 ± 3.6 M⊕ and a radius of 4.09 ± 0.17 R⊕. For K2-222b, we measure a mass of 8.0 ± 1.8 M⊕ and a radius of 2.35 ± 0.08 R⊕. According to model predictions, K2-79b is a highly irradiated Uranus analog and K2-222b hosts significant amounts of water ice. We also present a RV solution for a candidate second companion orbiting K2-222 at 147.5 days.
KW - Exoplanet astronomy
KW - Stellar activity
U2 - 10.3847/1538-3881/ac3141
DO - 10.3847/1538-3881/ac3141
M3 - Article
SN - 0004-6256
VL - 163
JO - The Astronomical Journal
JF - The Astronomical Journal
IS - 2
M1 - 41
ER -