2026A&A...707A.275J

Aims. We have compiled a list of blue lurker (BL) candidates in open clusters using the available rotation catalogs. Blue lurkers are rejuvenated main-sequence stars hidden among normal main-sequence stars on color-magnitude diagrams of star clusters. In comparison to BLs, blue straggler stars, which formed via similar mass transfers or mergers, occupy a distinct space in color-magnitude diagrams.
Methods. Blue lurkers can be identified by their unusually faster rotation compared to similar mass stars, which is a signature of recent accretion, or by the presence of a companion (e.g., an extremely low mass white dwarf), which can only be formed by mass donation. We searched for fast-rotating stars on the main sequence of open clusters using Kepler, TESS, and spectroscopic rotation indicators, such as rotation periods and v sin i measurements.
Results. We identified 97 new BL candidates across 35 open clusters, almost tripling the previously known sample of 36. Based on the estimated completeness of ≈3%, thousands of BLs are likely hidden within the cluster population. Detailed spectroscopic and time series analyses will be essential to confirming their mass-transfer histories.