Po Chih Hsu (Department of Atmospheric Science, National Central University, Zhongli District, Taoyuan City, Taiwan);Wen-Ping Chen (Graduate Institute of Astronomy, National Central University, Zhongli District, Taoyuan City, Taiwan)
Stars are formed in groups out of giant molecular clouds. Those that survive the dispersing processes become the open clusters we are now witnessing. With age, such a cluster dissolves, due to internal dynamics and external perturbations, and supplies the Galactic disk population. Star clusters are to stars therefore as families to individuals in the Galactic society, and serve as testbeds of stellar evolutionary theories. Double star clusters in particular provide tantalizing environments for stellar dynamics. Here we present the study of NGC 869 and NGC 884 (aka h and k Persei, roughly 1.28 Myr old), with the Gaia eDR3 data. With high-precision proper motion and parallax measurements, we identified member stars associated with each cluster, and possible lingering stars vulnerable to dynamic ejection by the two clusters. We will discuss the implication of such stellar ejection on the fate of a double cluster.