Stellar Paternity Tests: Matching High-Latitude B Stars to the Open Clusters of their Birth

TL;DR

This study uses Gaia DR3 data to trace the origins of high-latitude B stars, identifying their likely birth clusters, ejection mechanisms, and travel histories to understand their presence outside typical star-forming regions.

Contribution

The paper introduces a method combining kinematic trajectories and cluster age analysis to identify the birthplaces and ejection mechanisms of high-latitude B stars.

Findings

Identified probable birth clusters for five high-latitude B stars.

Estimated ejection velocities and travel times for these stars.

Discussed possible ejection mechanisms and origins for the stars.

Abstract

OB stars generally form in open clusters within the Milky Way's thin disk, so when they are found at high Galactic latitudes, it is thought that they were ejected from their birth clusters during the past few tens of millions of years. Using Gaia Data Release 3 (hereafter DR3) data, we traced the kinematic trajectories of 39 high-latitude B-type stars and 447 Galactic open clusters with high-quality astrometry to search for moments of past intersection. In cases where we found matching trajectories, we also considered the clusters' HR diagrams to confirm parent-orphan pairs have matching ages. Further analysis of the clusters' core environments allowed us to determine a probable ejection mechanism. Through these paternity tests, we have identified possible origins for five of these orphaned B-type stars. Here we present the likely travel times, ejection velocities, and a discussion of the runaway mechanism for each case. We also identify one star whose trajectory did not bring it near the disk during the time period of our analysis, and we discuss its possible origins as well.