Kavli Affiliate: Sara Seager
| First 5 Authors: David J. Armstrong, Ares Osborn, Vardan Adibekyan, Elisa Delgado-Mena, Saeed Hojjatpanah
| Summary:
We report the discovery of two exoplanets orbiting around HD 212729
(TOI,1052, TIC 317060587), a $T_{rm eff}=6146$K star with V=9.51 observed by
TESS in Sectors 1 and 13. One exoplanet, TOI-1052b, is Neptune-mass and
transits the star, and an additional planet TOI-1052c is observed in radial
velocities but not seen to transit. We confirm the planetary nature of
TOI-1052b using precise radial velocity observations from HARPS and determined
its parameters in a joint RV and photometry analysis. TOI-1052b has a radius of
$2.87^{+0.29}_{-0.24}$ R$_{oplus}$, a mass of $16.9pm 1.7$ M$_{oplus}$, and
an orbital period of 9.14 days. TOI-1052c does not show any transits in the
TESS data, and has a minimum mass of $34.3^{+4.1}_{-3.7}$ M$_{oplus}$ and an
orbital period of 35.8 days, placing it just interior to the 4:1 mean motion
resonance. Both planets are best fit by relatively high but only marginally
significant eccentricities of $0.18^{+0.09}_{-0.07}$ for planet b and
$0.24^{+0.09}_{-0.08}$ for planet c. We perform a dynamical analysis and
internal structure model of the planets as well as deriving stellar parameters
and chemical abundances. The mean density of TOI-1052b is $3.9^{+1.7}_{-1.3}$ g
cm$^{-3}$ consistent with an internal structure similar to Neptune. A nearby
star is observed in Gaia DR3 with the same distance and proper motion as
TOI-1052, at a sky projected separation of ~1500AU, making this a potential
wide binary star system.
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