A rotation-based census of blue lurker candidates in open clusters

TL;DR

This study identifies 97 new blue lurker star candidates in open clusters by analyzing stellar rotation data, significantly expanding the known sample and suggesting many more remain undiscovered.

Contribution

It presents a novel rotation-based method to identify blue lurker candidates, nearly tripling the known sample in open clusters.

Findings

Identified 97 new blue lurker candidates in open clusters.

Estimated that only about 3% of such stars have been detected so far.

Suggests thousands of hidden blue lurkers likely exist within cluster populations.

Abstract

Blue lurkers (BLs) are rejuvenated main-sequence stars hidden among normal main-sequence stars on color-magnitude diagrams of star clusters. In comparison, the blue straggler stars, formed via similar mass transfers or mergers, occupy a distinct space in the color-magnitude diagrams. We compile a list of BL candidates in open clusters using available rotation catalogs. BLs can be identified using either unusually faster rotation compared to similar mass stars, which is a signature of recent accretion, or the presence of a companion, which can only be formed by mass donation, e.g., an extremely low mass white dwarf. Here, 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. We identified 97 new BL candidates across 35 open clusters, almost tripling the previously known sample of 36. Based on the estimated completeness of $\approx$3\%, thousands of BLs are likely hidden within the cluster population. Detailed spectroscopic and time-series analyses will be essential to confirm their mass-transfer histories.