环双星系统中行星-行星之间的散射

Planet-planet scattering in circumbinary planetary systems

流体模拟的研究表明,如果多颗行星形成在环绕双星的气体盘中,行星之间的会聚迁移会导致行星之间的散射.本文系统研究了环双星的行星系统中两颗等质量行星(P型行星)之间的散射,目的是探讨散射对P型行星系统构型的影响.数值模拟的研究表明散射后只剩一颗行星的几率最大,一般>80%.从某种意义上说,伴星的存在有利于行星的存活,尤其是在靠近双星的地方.我们发现散射会导致行星的向外迁移,这和单恒星系统中的散射现象相反,此现象可以用来解释最近通过成像方法发现的远距离P型行星.即便对于等质量的行星,散射位置的不同会造成偏心率分布的多样性.在靠近双星的位置,幸存行星的偏心率较小;在远离双星的位置,剩余行星的偏心率较大.此外,P型行星之间的散射可使P型行星转变为围绕一颗主星运行的S型行星.

If multiple planets formed in a circumbinary disk, convergent migrations due to disk-planet interactions would cause dynamical instabilities among planets, which has been validated by hydrodynamical simulations. Based on the statistics of a set of 4-body integrations, various outcomes of planet-planet scattering （PPS） in a circumbinary system with two giant planets are presented in this paper. Numerical simulations indicate that retaining of one planet after PPS is the dominant outcome, with a probability of 〉80% in our simulations. In a sense, the binary companion doesn＇t seem to be a destroyer but a protector, especially when the scattering position of planets is near the binary. Scattering makes an outward migration of the remaining planet instead of inward migration which happens in single star systems The eccentricity distributions are diverse even for two equal-mass planets： near the binary, the final eccentricities are generally smaller; far away from the binary, the eccentricities are generally larger. This is apparently different from PPS phenomena happening in single star systems. We also find the phenomenon that PPS can turn a circumbinary planet into an ＇S-type＇ planet.