热海王星系统HD 106315的近2:1平运动共振捕获与轨道演化

Near 2:1 Mean Motion Resonance Capture and Orbital Evolution of A Hot-Neptune System:HD 106315

通过结合理论分析和数值模拟方法,可以对热海王星系统HD 106315轨道迁移中的近2:1平运动共振捕获机制以及潮汐作用下的演化过程进行研究.在轨道迁移阶段,初始轨道半长径、初始偏心率以及行星c的偏心率衰减系数K会对系统轨道构型产生影响.数值模拟结果显示当初始轨道半长径分别为ab^0.4 au、ac^0.8 au,偏心率eb和ec均小于0.03时, HD 106315b和HD 106315c在中央恒星的引力作用以及原行星盘粘滞作用下向内迁移, 65000 yr左右两颗行星均可迁移至当前观测位置附近并形成近2:1平运动共振捕获.此外,中央恒星的潮汐效应也可能会对行星系统共振构型产生影响,理论分析表明当行星潮汐耗散系数Q=100时,潮汐效应造成的轨道半长径衰减使系统轨道周期比发生的变化可能是系统脱离共振构型的原因.数值模拟结果显示, HD 106315系统内两颗行星Q103时,来自中央恒星的潮汐效应并不会使行星系统产生明显的偏心率和轨道半长径衰减,不足以使HD 106315行星系统在剩余寿命内脱离2:1平运动共振轨道构型.

In this work,we investigate the near 2:1 mean motion resonance capture scenario and tidal evolution for the hot-Neptune system HD 106315 by numerical simulations.To make a deeper understanding of migration for this system,we extensively explore the initial semi-major axis,eccentricity,as well as the attenuation coefficient of the eccentricity of HD 106315 c affecting the orbital configuration of the system.The numerical simulations show that when the initial orbital elements of two planets are ab^0.4 au,ac^0.8 au,eband eclower than 0.03,HD 106315 b and HD 106315 c can migrate to currently observed location,and form near 2:1 mean motion resonance.This scenario takes into account the effect of the central star and the viscosity of disk.In addition,tidal dissipation that originates from the host star,can influence the mean motion resonant configuration for planets.From a viewpoint of theoretical analysis and simulations,the results show that for tidal dissipation factor Q=100,the ratio of orbital period of two planets will change over the evolution.This may be indicative of the resonant departure for two planets in the system.However,tidal dissipation factor Q may be larger than 103 for the planets,therefore we may safely conclude that tidal effect does not play a major role in driving two Neptunian planets of the HD 106315 system move out of 2:1 mean motion resonance within the residual lifetime of the star.