在具有极向环双星盘的双星系统中逆行S型行星的形成
On the formation of retrograde S-type planets in binaries with a polar circumbinary disk
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中文总结 AI 辅助
本研究通过高分辨率流体动力学模拟，揭示了偏心质量不等双星的极向环双星盘可形成逆行迷你盘，为逆行S型行星提供原位形成通道，其出现率或高于当前估计。
中文摘要 AI 辅助
已在多个双星系统中观测到逆行S型行星，但其形成路径仍知之甚少。通过高分辨率流体动力学模拟，我们证明，围绕偏心、质量不等的双星的极向环双星盘能够在主星周围形成并维持一个逆行迷你盘，这为逆行S型行星提供了一条直接的原位形成通道。该迷你盘通过一条与极向盘略有错位的亚开普勒吸积流形成，初始时会经历冯·蔡佩尔-科兹艾-利多夫（ZKL）振荡，驱动轨道偏心率和倾角的耦合演化。内迷你盘不会无限振荡，而是会演化至超过ZKL临界倾角，与外盘解耦并稳定在逆行轨道上。这种演化对数值分辨率敏感：在之前较低分辨率的模拟中，迷你盘吸积时标过短，无法维持ZKL驱动的演化，因此不存在逆行结构。对于更高的盘粘度，迷你盘因吸积时标更短而保持近极向状态。由于原行星盘通常具有低粘度，我们的结果表明，逆行S型行星可从极向环双星盘周围的逆行迷你盘原位形成，其出现率可能高于当前估计值。
英文摘要
Retrograde S-type planets have been observed in several binary systems, yet their formation pathway remains poorly understood. With high-resolution hydrodynamic simulations, we demonstrate that a polar circumbinary disk around an eccentric, unequal-mass binary can form and sustain a retrograde mini disk around the primary star. This provides a direct in-situ formation channel for retrograde S-type planets. The mini disk forms via a sub-Keplerian accretion stream that is slightly misaligned from the polar disk. The mini disk initially undergoes von Zeipel-Kozai-Lidov (ZKL) oscillations, driving coupled eccentricity and inclination evolution. Rather than oscillating indefinitely, the inner mini disk evolves past the critical ZKL inclination, decouples from the outer disk, and settles into a stable retrograde orbit. This evolution is sensitive to numerical resolution: the retrograde configuration is absent in previous lower-resolution simulations, where the mini disk accretion timescale is too short to sustain ZKL-driven evolution. For a higher disk viscosity, the mini disk remains near-polar due to a shorter accretion timescale. Since protoplanetary disks typically have low viscosity, our results suggest that retrograde S-type planets can form in-situ from retrograde mini disks around polar circumbinary disks, and their occurrence rate may be higher than currently estimated.
