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- Li, Daohai, et al.
(author)
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Making hot Jupiters in stellar clusters - II. Efficient formation in binary systems
- 2024
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In: Monthly Notices of the Royal Astronomical Society. - 1365-2966. ; 527:1, s. 386-402
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Journal article (peer-reviewed)abstract
- Observations suggested that the occurrence rate of hot Jupiters (HJs) in open clusters is largely consistent with the field (∼ 1 per cent) but in the binary-rich cluster M67, the rate is ∼ 5 per cent. How does the cluster environment boost HJ formation via the high-eccentricity tidal migration initiated by the extreme-amplitude von Zeipel–Lidov–Kozai (XZKL) mechanism forced by a companion star? Our analytical treatment shows that the cluster’s collective gravitational potential alters the companion’s orbit slowly, which may render the star–planet–companion configuration XZKL-favourable. We have also performed direct Gyr N-body simulations of the star cluster evolution and XZKL of planets’ orbit around member stars. We find that an initially single star may acquire a companion star via stellar scattering and the companion may enable XZKL in the planets’ orbit. Planets around an initially binary star may also be XZKL-activated by the companion. In both scenarios, the companion’s orbit has likely been significantly changed by stellar scattering and the cluster potential before XZKL occurs. Across different cluster models, 0.8–3 per cent of the planets orbiting initially single stars have experienced XZKL while the fraction is 2–26 per cent for initially binary stars. Around a star that is binary at 1 Gyr, 13–32 per cent of its planets have undergone XZKL, and combined with single stars, the overall XZKL fraction is 3–21 per cent, most affected by the cluster binarity. If 10 per cent of the stars in M67 host a giant planet, our model predicts an HJ occurrence rate of ∼ 1 per cent. We suggest that HJ surveys target old, high-binarity, not-too-dense open clusters and prioritize wide binaries to maximize HJ yield.
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| 2. |
- Mustill, Alexander J., et al.
(author)
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The formation of transiting circumplanetary debris discs from the disruption of satellite systems during planet-planet scattering
- 2024
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In: Monthly Notices of the Royal Astronomical Society. - 0035-8711. ; 530:4, s. 3606-3616
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Journal article (peer-reviewed)abstract
- Several stars show deep transits consistent with discs of roughly seen at moderate inclinations, likely surrounding planets on eccentric orbits. We show that this configuration arises naturally as a result of planet-planet scattering when the planets possess satellite systems. Planet-planet scattering explains the orbital eccentricities of the discs' host bodies, while the close encounters during scattering lead to the exchange of satellites between planets and/or their destabilization. This leads to collisions between satellites and their tidal disruption close to the planet. Both of these events lead to large quantities of debris being produced, which in time will settle into a disc such as those observed. The mass of debris required is comparable to a Ceres-sized satellite. Through N-body simulations of planets with clones of the Galilean satellite system undergoing scattering, we show that 90 per cent of planets undergoing scattering will possess debris from satellite destruction. Extrapolating to smaller numbers of satellites suggests that tens of per cent of such planets should still possess circumplanetary debris discs. The debris trails arising from these events are often tilted at tens of degrees to the planetary orbit, consistent with the inclinations of the observed discs. Disruption of satellite systems during scattering thus simultaneously explains the existence of debris, the tilt of the discs, and the eccentricity of the planets they orbit.
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