Photoelectric search for peculiar stars in open clusters XV. Feinstein 1, NGC 2168, NGC 2323, NGC 2437, NGC 2547, NGC 4103, NGC 6025, NGC 6633, Stock 2, and Trumpler 2
2014
The chemically peculiar (CP) stars of the upper main sequence
are mainly characterized by strong overabundances of heavy
elements. Two subgroups (CP2 and CP4) have strong local
magnetic fields which make them interesting targets for
astrophysical studies. This star group, in general, is often
used for the analysis of stellar formation and evolution in the
context of diffusion as well as meridional circulation. In
continuation of a long term study of CP stars (initiated in the
1980s), we present new results based on photoelectric
measurements for ten open clusters that are, with one
exception, younger than 235 Myr. The very efficient tool of
Delta a photometry was applied. It samples the flux depression
at 5200 angstrom typically for CP stars. In addition, it is
able to trace emission line Be/Ae and lambda Bootis stars.
Virtually all CP2 and CP4 stars can be detected via this tool,
and it has been successfully applied even in the Large
Magellanic Cloud. For all targets in the cluster areas, we
performed a kinematic membership analysis. We obtained new
photoelectric Delta a photometry of 304 stars from which 207
objects have a membership probability higher than 50%. Our
search for chemically peculiar objects results in fifteen
detections. The stars have masses between 1.7 M(sun) and 7.7
M(sun) and are between the zero- and
terminal-age-main-sequence. We discuss the published spectral
classifications in the light of our Delta a photometry and
identify several misclassified CP stars. We are also able to
establish and support the nature of known bona fide CP
candidates. It is vital to use kinematic data for the
membership determination and also to compare published spectral
types with other data, such as Delta a photometry. There are no
doubts about the accuracy of photoelectric measurements,
especially for stars brighter than 10th magnitude.
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