大样本恒星演化研究组知识库

We show that the angular momentum exchange mechanism governing the evolution of mass-transferring binary stars does not apply to Roche lobe filling planets, because most of the angular momentum of the mass-transferring stream is absorbed by the host star. Apart from a correction for the difference in specific angular momentum of the stream and the centre of mass of the planet, the orbit does not expand much on Roche lobe overflow. We explore the conditions for dynamically unstable Roche lobe overflow as a function of planetary mass and mass and radius (age) of host star and equation of state of planet. For a Sun-like host, gas giant planets in a range of mass and entropy can undergo dynamical mass transfer. Examples of the evolution of the mass transfer process are given. Dynamic mass transfer of rocky planets depends somewhat sensitively on equation of state used. Silicate planets in the range 1 < M-p < 10M(circle plus) typically go through a phase of dynamical mass transfer before settling to slow overflow when their mass drops to less than 1 M-circle plus.