Abstract
ABSTRACT K2-19 hosts a planetary system composed of two outer planets, b and c, with size of 7.0 ± 0.2 R⊕ and 4.1 ± 0.2 R⊕, and an inner planet, d, with a radius of 1.11 ± 0.05 R⊕. A recent analysis of Transit-Timing Variations (TTVs) suggested b and c are close to but not in 3:2 mean motion resonance (MMR) because the classical resonant angles circulate. Such an architecture challenges our understanding of planet formation. Indeed, planet migration through the protoplanetary disc should lead to a capture into the MMR. Here, we show that the planets are in fact, locked into the 3:2 resonance despite circulation of the conventional resonant angles and aligned periapses. However, we show that such an orbital configuration cannot be maintained for more than a few hundred million years due to the tidal dissipation experienced by planet d. The tidal dissipation remains efficient because of a secular forcing of the innermost planet eccentricity by planets b and c. While the observations strongly rule out an orbital solution where the three planets are on close to circular orbits, it remains possible that a fourth planet is affecting the TTVs such that the four planet system is consistent with the tidal constraints.
Highlights
The numerous planet discoveries over the past decades have revealed the large diversity in sizes and orbital architecture of exoplanetary systems (Winn & Fabrycky 2015)
Such configurations have been observed for various systems observed through both radial velocities (RV) and with the analysis of Transit-Timing Variations (TTV, see e.g. Agol et al 2005; Holman & Murray 2005)
We show that the outer planets are inside the mean motion resonance (MMR) and that they are coupled secularly to the inner planet
Summary
The numerous planet discoveries over the past decades have revealed the large diversity in sizes and orbital architecture of exoplanetary systems (Winn & Fabrycky 2015). We expect planets in resonant chains to have close to circular orbits due to the eccentricity damping during the migration (Cresswell & Nelson 2008). Such configurations have been observed for various systems observed through both radial velocities (RV) and with the analysis of Transit-Timing Variations Petigura et al (2020) report that the system is stable in numerical simulations but is strongly angular momentum deficit (AMD) unstable (Laskar & Petit 2017) and not protected by the resonance Such a configuration is in tension with our current understanding of planet formation. We highlight the constraints on the three planet best fit and discuss whether the TTVs might be affected by an unmodelled effect, including the presence of a planet not yet detected
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
