Exoplanets & Exomoons

The Six-planet Resonant Chain Of HD 110067

By Keith Cowing
Status Report
May 10, 2024
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The Six-planet Resonant Chain Of HD 110067
Cumulative fraction of 350 systems that destabilized within 25 Myr. 99 % of the non-resonant systems with properties consistent with the observations were unstable, as opposed to 11 % of systems initialized in a six-planet resonant chain (via a disk migration simulation). Systems in which only a subset of the planets are captured into a resonant chain were also mostly unstable. — astro-ph.EP

HD 110067 is the brightest star known to have six transiting planets. Each adjacent pair of planets has a period ratio that is nearly equal to a ratio of small integers, suggesting the planets are in a chain of mean-motion resonances, but the limited timespan of the available data has prevented firm conclusions.

Here, we show that the requirement of long-term dynamical stability implies that all six planets are very likely to form a resonant chain. Dynamical simulations of non-resonant systems with initial conditions compatible with the available data almost always suffer an instability within 25 Myr (∼0.3% of the system’s age).

Assuming the system is in resonance, we place upper limits on the planets’ eccentricities, and lower limits on the masses of the planets that have not yet been measured. We also predict the characteristics of transit timing variations and the values of the three-body libration centers.

Evolution of adjacent planet period ratios, orbital eccentricities, and three-body resonant angles during an example convergent migration simulation (in this case, K = 114). Adjacent planet pairs are captured into two-body MMRs outside-in, beginning with planets f-g and ending with planets b-c. Each planet obtains a non-zero eccentricity through this process, and three-body resonant angles librate with small amplitudes (two-body resonant angles also librate). Before carrying out our long-term N-body simulations, we adiabatically remove the eccentricity and semi-major axis damping and provide a random kick to the planets’ eccentricities.– astro-ph.EP

Caleb Lammers, Joshua N. Winn

Comments: 8 pages, 5 figures, 2 tables. Submitted to ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2405.04527 [astro-ph.EP] (or arXiv:2405.04527v1 [astro-ph.EP] for this version)

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Submission history
From: Caleb Lammers
[v1] Tue, 7 May 2024 17:57:32 UTC (1,702 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻