What can we expect from a census of Ap stars in open star clusters in the Galaxy and beyond?

Year, pages: 2008, 385 - 390

We discuss the presence of magnetic peculiar stars in open clusters on the basis of photometric identification, in a sample that covers not only the solar neighbourhood but also wider galactic regions. Our study includes the possible influence of metallicity and/or other environmental properties. The compactness of a cluster is investigated as a parameter in Ap-star formation. For that purpose we use the classical p-m-r "richness" groups defined by Trumpler (1930), together with approximate cluster volumes derived from a recent study of cluster diameters by van den Bergh (2006). Basing our study on a sample of 80 galactic clusters with published Δa photometry, we notice (a) that the Trumpler richness groups correspond to distinctly separated mean cluster diameters (2.0/3.4/4.9 pc) and (b) that the resulting densities (Ap stars per pc³) point overwhelmingly to the p group as the principal domain of Ap stars. A special feature is the prevailing appearance of p-group Ap stars alone in the inner galactic quadrants, unaccompanied by parallel behaviour of the m and r groups. Whether or not this is a metallicity effect has to be substantiated by the including additional clusters to improve the statistics. It does seem to be the case in the Large Magellanic Cloud, according to a study of a photometric sample of Ap stars, though the frequency is clearly lower on account of the lower metallicity of this satellite galaxy.

Maitzen, H., Paunzen, E., Netopil, M. 2008. What can we expect from a census of Ap stars in open star clusters in the Galaxy and beyond?. In Contributions of the Astronomical Observatory Skalnaté Pleso, vol. 38, no.2, pp. 385-390. 1335-1842.

Maitzen, H., Paunzen, E., Netopil, M. (2008). What can we expect from a census of Ap stars in open star clusters in the Galaxy and beyond?. Contributions of the Astronomical Observatory Skalnaté Pleso, 38(2), 385-390. 1335-1842.