Revisit of 77 Clusters Candidates with Multiple Main Sequences using Gaia DR3

Abstract

Abstract Gaia DR3 data provide the latest and full astrometric data for more than 1.5 billion sources, and these allow us to revisit the 77 special open cluster candidates collected from LISC star cluster catalog. According to their unclear color–magnitude-diagram (CMD) morphology, they are difficult to be ensured as real open clusters (OCs), and their cluster properties are still poorly known. We perform a cluster census by reidentification for these clusters using pyUPMASK based on the photometric and astrometric stellar information. We have redetected these 77 objects and they should be real OCs, of which five clusters are potential binary clusters. Their basic parameters are obtained by fitting isochrones to observed CMDs. Our results show that their CMDs display more clean main sequences (MSs) and less member stars lying on the right of lower MSs relative to most of clusters in our initial sample, but broad MSs have not changed significantly. We suggest that efficient clustering algorithm combined with precision data can only partly reduce some stars lying on the right of lower MSs, and a simple stellar population of binary and rotating stars can partly reproduce multiple MS phenomena, including split and broad MSs.