TY - JOUR
T1 - K2-79b and K2-222b: 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
Y1 - 2022
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 - Journal article
SN - 0004-6256
VL - 163
JO - Astronomical Journal
JF - Astronomical Journal
IS - 2
M1 - 41
ER -