Mass determination of the three long-period Neptune- and sub-Neptune-sized planets transiting TOI-282

Le résumé fourni par la source

TOI-282 is a bright (V = 9.38) F8 main-sequence star known to host three transiting long-period ( P b = 22.9 d, P c = 56.0 d, and P d = 84.3 d) small ( R p ≈ 2–4 R ⊕ ) planets. The orbital period ratio of the two outermost planets, namely TOI-282 c and d, is close to the 3:2 commensurability, suggesting that the planets might be trapped in a mean motion resonance. We combined space-borne photometry from the TESS telescope with high-precision HARPS and ESPRESSO Doppler measurements to refine orbital parameters, measure the planetary masses, and investigate the architecture and evolution of the system. We performed a Markov chain Monte Carlo joint analysis of the transit light curves and radial velocity time series, and carried out a dynamical analysis to model transit timing variations and Doppler measurements along with N -body integration. In agreement with previous results, we found that TOI-282 b, c, and d have radii of R b = 2.69 ± 0.23 R ⊕ , R c = 4.13 −0.14 +0.16 R ⊕ , and R d = 3.11 ± 0.15 R ⊕ , respectively. We measured planetary masses of M b = 6.2 ± 1.6 M ⊕ , M c = 9.2 ± 2.0 M ⊕ , and M d = 5.8 −1.1 +0.9 M ⊕ , which imply mean densities of ρ b = 1.8 −0.6 +0.7 g cm −3 , ρ c = 0.7 ± 0.2 g cm −3 , and ρ d = 1.1 −0.2 +0.3 g cm −3 , respectively. The three planets may be water worlds, making TOI-282 an interesting system for future atmospheric follow-up observations with JWST and ELT.

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