The evolutionary state of the chemically peculiar members of the open cluster NGC 2516

Abstract

ABSTRACT We aim at establishing safe membership and evolutionary status of 11 chemically peculiar (CP) stars that are residing in the domain of the open cluster NGC 2516 and are frequently referred to as cluster members. We queried the Gaia EDR3 catalogue in an area with a radius of 1° and selected 37 508 stars brighter than G = 19 mag. The cluster membership was determined in parallax-proper motion-space and 719 probable and 764 possible members were found. The obtained average astrometric and photometric parameters of the cluster are in good agreement with the most recent literature data. The evolutionary status of the target stars was determined with respect to Padova isochrones. After minor adjustments including the metallicity, the reddening, and the transformation scale variation, a perfect fit of the model to the observations over the whole observed magnitude range was achieved. Only 5 of the 11 considered CP stars could be classified as highly probable cluster members. Among the Ap/Bp stars with previously detected magnetic fields HD 65987 and HD 65712 have a high membership probability and the magnetic star CPD−60 944B is a possible cluster member. Further we discuss the blue straggler nature of HD 66194 and the magnetic star HD 65987. To our knowledge, HD 65987 is currently the only known blue straggler, with a field of the order of a few hundred Gauss. The most striking result of our study is that the strongly magnetic A0p star HD 66318 with previously reported very low fractional age does not belong to the NGC 2516 cluster at a high level of confidence.