Discovery and characterisation of two Neptune-mass planets orbiting HD 212729 with TESS

Abstract

We report the discovery of two exoplanets orbiting around HD 212729 (TOI\,1052, TIC 317060587), a $T_{\mathrm{eff}}=6146$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 $2.87_{-0.24}^{+0.29}$ R${}_{\oplus }$, a mass of $16.9\pm 1.7$ 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 $34.3_{-3.7}^{+4.1}$ 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 $0.18_{-0.07}^{+0.09}$ for planet b and $0.24_{-0.08}^{+0.09}$ 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 $3.9_{-1.3}^{+1.7}$ 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.

Accepted to MNRAS. 11 pages

References in corpus (32)

• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• Basic physical parameters of a selected sample of evolved stars
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• A new code for automatic determination of equivalent widths: Automatic Routine for line Equivalent widths in stellar Spectra (ARES)
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• Determining stellar macroturbulence using asteroseismic rotational velocities from Kepler
• Transit Least Squares: Optimized transit detection algorithm to search for periodic transits of small planets
• ARES v2 - new features and improved performance
• A generalized bayesian inference method for constraining the interiors of super Earths and sub-Neptunes
• exoplanet: Gradient-based probabilistic inference for exoplanet data & other astronomical time series
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• Gaia Data Release 3: Apsis II -- Stellar Parameters
• Abundance to age ratios in the HARPS-GTO sample with Gaia DR2: Chemical clocks for a range of [Fe/H]
• SWEET-Cat 2.0: The Cat just got SWEETer; Higher quality spectra and precise parallaxes from GAIA eDR3
• Oxygen abundances in G- and F-type stars from HARPS
• Radial Velocity Data Analysis with Compressed Sensing Techniques
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program IV. Carbon and C/O ratios for Galactic stellar populations and planet hosts
• The HADES RV Programme with HARPS-N@TNG. III. Flux-flux and activity-rotation relationships of early-M dwarfs
• Mass determinations of the three mini-Neptunes transiting TOI-125
• Chemical abundances of 1111 FGK stars from the HARPS-GTO planet search sample. III. Sulfur
• Truly eccentric. II. When can two circular planets mimic a single eccentric orbit?
• When, where, and how many planets end up in first-order resonances?
• Architectures of Compact Multi-planet Systems: Diversity and Uniformity
• TOI-220 $b$: a warm sub-Neptune discovered by TESS
• TESS and HARPS reveal two sub-Neptunes around TOI 1062

Cited by in corpus (2)

• TOI-5005 b: A super-Neptune in the savanna near the ridge
• Resonant sub-Neptunes are puffier