We report the discovery of two exoplanets orbiting around HD 212729 (TOI 1052, TIC 317060587), a Teff = 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 R⊙, a mass of 16.9 ± 1.7 M⊙, and an orbital period of 9.14 d. TOI-1052c does not show any transits in the TESS data, and has a minimum mass of M⊙ and an orbital period of 35.8 d, 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 for planet b and 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 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 1500 au, making this a potential wide binary star system.
- planets and satellites: detection
- planets and satellites: individual: (TOI-1052, TIC 317060587)