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

David J. Armstrong*, Ares Osborn, Vardan Adibekyan, Elisa Delgado-Mena, Saeed Hojjatpanah, Steve B. Howell, Sergio Hoyer, Henrik Knierim, Sergio G. Sousa, Keivan G. Stassun, Dimitri Veras, David R. Anderson, Daniel Bayliss, François Bouchy, Christopher J. Burke, Jessie L. Christiansen, Xavier Dumusque, Marcelo Aron Fetzner Keniger, Andreas Hadjigeorghiou, Faith HawthornRavit Helled, Jon M. Jenkins, David W. Latham, Jorge Lillo-Box, Louise D. Nielsen, Hugh P. Osborn, Jose Rodrigues, David Rodriguez, Nuno C. Santos, Sara Seager, Paul A. Strøm, Guillermo Torres, Joseph D. Twicken, Stephane Udry, Peter J. Wheatley, Joshua N. Winn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)5804-5816
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume524
Issue number4
DOIs
StatePublished - 1 Oct 2023
Externally publishedYes

Keywords

  • planets and satellites: detection
  • planets and satellites: individual: (TOI-1052, TIC 317060587)

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