Searching for high-velocity stars in the globular cluster M22

Abstract

High-velocity stars in globular cluster are important tools for the studies of internal star dynamics. In this work, we attempt to search high-velocity stars in the globular cluster M22 using high-precision peoper-motion and photometric data. We find 90 high-velocity stars in this cluster, the tangential velocities of these stars are determined to be in the range of 43–84 km/s, the average uncertainty is about 12 km/s. The central escape velocity of M22 is estimated to be about 31 km/s, which is significantly lower than the spatial velocities of these high-velocity stars. The results of our analysis indicate that these high-velocity stars should be accelerated within the recent 1 Ma, and they will escape out of the cluster within the next 1 Ma. Possible origins for these high-velocity stars are discussed.