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

D. J. Armstrong, A. Osborn, V. Zh. Adibekyan, E. Delgado-Mena, S. Hojjatpanah, S. B. Howell, S. Hoyer, H. Knierim, S. G. Sousa, K. G. Stassun, D. Veras, D. R. Anderson, D. Bayliss, F. Bouchy, C. J. Burke, J. L. Christiansen, X. Dumusque, M. A. F. Keniger, A. Hadjigeorghiou, F. Hawthorn, R. Helled, J. M. Jenkins, D. W. Latham, J. Lillo-Box, L. D. Nielsen, H. P. Osborn, J. Rodrigues, D. R. Rodriguez, N. C. Santos, S. Seager, P. A. Strøm, G. Torres, J. D. Twicken, S. Udry, P. J. Wheatley, J. N. Winn


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 2.87-0.24+0.29R, 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 34.3-3.7+4.1M 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 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 ~1500 au, making this a potential wide binary star system.

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

Monthly Notices of the Royal Astronomical Society
Volume 524, Issue 4, Page 12
2023 October

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia