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
| Authors | |
|---|---|
| Year of publication | 2014 |
| Type | Article in Periodical |
| Magazine / Source | ASTRONOMY & ASTROPHYSICS |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1051/0004-6361/201423521 |
| Field | Astronomy and astrophysics |
| Keywords | stars: chemically peculiar; stars: early-type; techniques: photometric; open clusters; associations: general |
| Description | 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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