Flora小行星族自转特性研究

Study on the Spin Characteristics of the Flora Asteroid Family

小行星族作为灾变碰撞的残留物,其基础物理性质提供了其母体以及后续演化信息.其中轨道以及自转特性分别反映了Yarkovsky效应以及Yarkovsky-O’Keefe-Radzievskii-Paddack效应(YORP效应)对于小行星族演化的影响.基于小行星光变数据库(Asteroid Lightcurve Database),通过对Flora小行星族自转速率分布进行研究,发现随着直径减小,族成员自转速率倾向于主要集中在3–5 d^(-1)的范围内.同时,可以注意到Flora小行星族整体表现出更倾向于顺行自转状态的现象,但对于轨道半长轴小于2.2au的成员来说,其顺行自转与逆行自转状态成员数目比接近于近地小行星中顺逆行自转状态源1:3的比例;此外,对于轨道半长轴大于2.2 au且具有顺行自转状态的部分族成员,在轨道半长轴-绝对星等分布中表现出聚集现象,并在聚集区域中有9颗成员展现出类似Slivan状态特征.

Asteroid families are the remnants of the catastrophic collision,and their fundamental physical properties provide us the information of their parent bodies and evolutions.Especially,the orbit and spin characteristics can reflect the influences of the Yarkovsky effect and the Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP)effect on the evolution of the asteroid family,respectively.Based on the Asteroid Lightcurve Database(LCDB),the spin rate distribution of the Flora asteroid family is studied,and a tendency that the spin rates of the small Flora family asteroids assemble primarily in the range of 3-5 d-1 is found;by analysis on the spin states of the Flora family asteroids,a phenomenon can be also found that the most majority of this asteroid family members lie in the prograde rotating state.However,for some Flora family asteroids which locate in the semi-major axis less than 2.2 au,the ratio between the number of prograde rotating bodies and that of retrograde ones is similar to that of the near-earth asteroids which have the corresponding ratio of 1:3.Furthermore,for those prograde rotating Flora family asteroids whose semi-major axis is more than 2.2 au,a portion of the members assemble in a special range reflecting a certain relationship between the semi-axis and the absolute magnitude,in which nine members show the similar feature of the Slivan state.