Table 1
Parameters of several representative hierarchical systems.
| Perturbation from an outer planetary companion | ||||||||
|---|---|---|---|---|---|---|---|---|
| Parameter | R⋆ (R⊙) | P⋆ (day) | J2 (10−4) | a1 (au) | m2 (MJ) | a2 (au) | ϵ⋆p | (°) |
| Case I | 2.0 | 5.0 | 2.87 | 0.1 | 1.0 | 2.0 | 41.7 | 45.3 |
| Case II | 1.5 | 5.0 | 1.21 | 0.1 | 1.0 | 2.0 | 9.9 | 47.5 |
| Case III | 1.5 | 5.0 | 1.21 | 0.1 | 1.0 | 1.0 | 1.24 | 71.8 |
| Case IV | 1.5 | 3.0 | 3.36 | 0.05 | 1.0 | 0.5 | 13.7 | 46.7 |
| K2-290A(1) | 2.5 | 3.0 | 13.1 | 0.0923 | 0.774 | 0.305 | 2.42 | 56.8 |
| K2-290A(2) | 2.0 | 3.0 | 6.70 | 0.0923 | 0.774 | 0.305 | 0.79 | − |
| HD 3167 | 1.5 | 5.0 | 1.42 | 0.018 | ![]() |
158.6 | 44.8 | |
| Perturbation from the outer disk | ||||||||
| Parameter | R⋆ (R⊙) | P⋆ (day) | J2 (10−4) | a1 (au) | md (M⊙) | rc | ϵ⋆p | (°) |
| Case 1 | 2.0 | 5.0 | 2.87 | 0.1 | 0.02 | 2 | 99.5 | 44.9 |
| Case 2 | 1.5 | 5.0 | 1.21 | 0.1 | 0.02 | 1.5 | 13.3 | 46.7 |
Notes. The values of ϵ⋆p and
are calculated by using Eq. (35) and the bifurcation condition (Eq. (37)), respectively. If the perturbation is from the outer disk considering nonhomologous disk dissipation, ϵ⋆p is calculated by ϵ⋆p = ϕ⋆,1/ϕdout,1, where ϕdout,1 is given by Eq. (19). The parameter J2 is calculated through Eq. (39). Except R⋆ and P⋆, the other system parameters of the K2-290A and HD 3167 systems are taken from current observations (Hjorth et al. 2021; Bourrier et al. 2022). For HD 3167, the outer three planets collectively act as an outer perturbation, as discussed in Fu & Wang (2024). Except K2-290A with m⋆ = 1.19M⊙ and HD 3167 with m⋆ = 0.852M⊙, all other systems have stellar masses of m⋆ = 1m⊙. The disk’s outer truncation is set to be rout = 50 au.
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![$\[\psi_{\star 0, \text {crit}}^{P}\]$](/articles/aa/full_html/2026/01/aa55897-25/aa55897-25-eq103.png)
![$\[\sum m_{j} / a_{j}^{3}=41.05\]$](/articles/aa/full_html/2026/01/aa55897-25/aa55897-25-eq104.png)
![$\[\psi_{\star 0, \text {crit}}^{P}\]$](/articles/aa/full_html/2026/01/aa55897-25/aa55897-25-eq105.png)