Chemically peculiar stars as members of open clusters

ABSTRACT The chemically peculiar (CP) stars of the upper main sequence are excellent astrophysical laboratories to test the diffusion, mass-loss, rotational mixing, and pulsation in the (non-)presence of a stable local magnetic field. These processes are time-dependent. The age estimation of Galactic field stars suffers from several limitations. Therefore, studying members of star clusters overcomes these difficulties. We matched the most recently published catalogues of star clusters and CP stars. For the matching, we used the newest Gaia Data Release. We also used the $\Delta$a photometry tool to further distinguish between the CP subgroups. We found 595 CP stars in 408 star clusters of all ages. Furthermore, we report on misclassified metallic line stars (Am or CP1) and objects with no CP classification. The distribution of magnetic and non-magnetic CP stars on the main sequence seems different. We do not detect very young and very old CP stars showing rotationally induced variability. CP members of star clusters help to study all relevant processes responsible for this phenomenon in more detail. Still, a larger sample is desired to put tighter constraints on models.