Exoplanets’ properties are directly linked to that of their host star. This is even more true in the case of transiting exoplanets, where the planetary radius cannot be derived if the stellar radius is unknown. Interferometry seems the best technique in this context, as it provides in a quasi-direct way and with exquisite precision the stellar radii. Moreover, the transit light curve can be used to directly obtain the stellar density, and thus the stellar mass. We apply this technique to the system of HD 219134, which hosts two transiting super-Earths. Using these observa- tional techniques and the correlations between the measured parameters, we directly derive new stellar radius, density and mass : R⋆ = 0.726 ± 0.014 R⊙ , ρ⋆ = 1.82 ± 0.19 ρ⊙ , M⋆ = 0.696±0.078 M⊙ . This yields new planetary parameters, and in particular, we find that the two transiting exoplanets show different densities despite similar masses. This can be explained by three hypothesis, among which one suggests that tides heat the internal part of the innermost planet, leading to a molten mantle with lower density.
From the stellar properties of HD 219134 to the internal compositions of its transiting exoplanets
Context. The harvest of exoplanet discoveries has opened the area of exoplanet characterisation. But this cannot be achieved without a careful analysis of the host star parameters. Aims. The system of HD 219134 hosts two transiting exoplanets and at least two additional non-transiting exoplanets. We revisit the properties of this system using direct measurements of the stellar parameters to investigate the composition of the two transiting exoplanets. Methods. We used the VEGA/CHARA interferometer to measure the angular diameter of HD 219134. We also derived the stellar density from the transits light curves, which finally gives a direct estimate of the mass. This allowed us to infer the mass, radius, and density of the two transiting exoplanets of the system. We then used an inference model to obtain the internal parameters of these two transiting exoplanets. Results. We measure a stellar radius, density, and mass of R ⋆ = 0.726 ± 0.014 R ⊙ , ρ ⋆ = 1.82 ± 0.19 ρ ⊙ , and M ⋆ = 0.696 ± 0.078 M ⊙ , respectively; there is a correlation of 0.46 between R ⋆ and M ⋆ . This new mass is lower than that derived from the C2kSMO stellar evolutionary more »
- Publication Date:
- NSF-PAR ID:
- 10193757
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 631
- Page Range or eLocation-ID:
- A92
- ISSN:
- 0004-6361
- Sponsoring Org:
- National Science Foundation
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- https://doi.org/10.1051/0004-6361/201936259
