A 2:1 Mean-motion Resonance Super-Jovian Pair Revealed by TESS, FEROS, and HARPS* *Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO programmes 105.20GX.001, 108.22A8.001, 110.23YQ.001, and MPG programmes 0106.A-9014, 0107.A-9003, 0108.A-9003, 0109.A-9003, 0110.A-9011.

Abstract

We report the discovery of a super-Jovian 2:1 mean-motion resonance (MMR) pair around the G-type star TIC 279401253, whose dynamical architecture is a prospective benchmark for planet formation and orbital evolution analysis. The system was discovered thanks to a single-transit event recorded by the Transiting Exoplanet Survey Satellite mission, which pointed to a Jupiter-sized companion with poorly constrained orbital parameters. We began ground-based precise radial velocity (RV) monitoring with HARPS and FEROS within the Warm gIaNts with tEss survey to constrain the transiting body’s period, mass, and eccentricity. The RV measurements revealed not one but two massive planets with periods of and days, respectively. A combined analysis of transit and RV data yields an inner transiting planet with a mass of M Jup and a radius of R Jup, and an outer planet with a minimum mass of M Jup, indicating a massive giant pair. A detailed dynamical analysis of the system reveals that the planets are locked in a strong first-order, eccentricity-type 2:1 MMR, which makes TIC 279401253 one of the rare examples of truly resonant architectures supporting disk-induced planet migration. The bright host star, V ≈ 11.9 mag, the relatively short orbital period (P b = days), and pronounced eccentricity (e = 0.448) make the transiting planet a valuable target for atmospheric investigation with the James Webb Space Telescope and ground-based extremely large telescopes.