A Low-speed Intruder Star in Hyades: A Temporary Residence

TL;DR

This paper reports the first observational evidence of a low-speed star temporarily residing in the Hyades cluster, indicating star intrusions can occur and be observed in real time.

Contribution

It provides the first observational evidence of a star intrusion into a cluster, highlighting the dynamic nature of star cluster memberships.

Findings

The star is a non-native member of Hyades.

The star's orbit suggests intrusion within the last 2 Myr.

The star may leave the cluster in the next 2 Myr.

Abstract

We hereby report a low-speed (about~21~km$\cdot$~s$^{-1}$ with respect to the Sun) intruder member in the Hyades cluster based on the data in the literature. The results show that the star is a non-native member star for the Hyades, with its radial velocity being smaller than the radial velocity of the Hyades cluster, even exceeding the standard deviation of the radial velocity of the cluster by a factor of 9. Furthermore, by analyzing and comparing the orbits of this star and its host, it may have intruded into its host in the past 2~Myr. If the star's current motion orbit remains unchanged, it may leave its host in the next 2~Myr. This implies that the intruder star may be temporarily residing in the cluster. This study presents the first observational evidence of a star intrusion into a cluster, which suggests that more evidence may be found.