2024/11/12 by Yubo Su, Dong Lai, Su, Yubo +1
Physics and Astronomy · #Astrophysics and Star Formation Studies #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2411.08094
openalex publication_date 2024/11/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The stellar obliquity of a planetary system is often used to help constrain the system's formation and evolution. One of the mechanisms to reorient the stellar spin involves a secular resonance crossing due to the dissipation of the protoplanetary disk when the system also has an inclined, distant (∼ 300 AU) binary companion. This mechanism is likely to operate broadly due to the ∼ 50% binary fraction of FGK dwarfs and can play an important role in setting the initial stellar obliquities prior to any dynamical evolution. In this work, we revisit this mechanism analytically for idealized, homologously evolving disk models and show that the resulting stellar obliquities are broadly distributed between 60^∘ and 180^∘ for most warm and cold planets. We further show that non-homologus disk dissipation, such as the development of a photoevaporatively-opened gap at ∼ 2 AU, can help maintain orbital alignment of warm planets, in agreement with observations. Our results represent the proper primordial obliquities for planetary systems with distant binary companions. They also represent the obliquities of stars with no present-day binary companions if these companions are dynamically unbound during the birth cluster phase of evolution, a process that occurs on a comparable timescale as the disk-driven obliquity excitation.