Periods of the “coupled” (T+) and “decoupled” (T−) free modes as a function of the moment of inertia, for our range of interior models. The blue horizontal lines represent the opposite of the first and the fourth orbital periods. Some interior models have T+ close to 703.51 years and other interior models have a period T− very close to 29.46 years, leading to a resonance. The red and green dots are the interior models that, thanks to a resonant amplification of ε1,s or ε4,s, can reach a shell obliquity as large as the observed one (see also Fig. 2).
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