The frequency of peculiar A and metallic-line stars in open clusters.

Abstract

view Abstract Citations (68) References (72) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The frequency of peculiar A and metallic-line stars in open clusters. Hartoog, M. R. Abstract MK spectral types were determined for 263 B and A stars in the southern galactic clusters NGC 2287, 2422, 2451, 2516, 2547, 3228, and 3532 in order to investigate the frequency of Ap and Am stars in galactic clusters. In these seven clusters 11 Ap stars and 203 normal B5 to AS dwarfs were found. This frequency is lower than that found in two independent field samples. When this sample is combined with published data for other clusters, a 2 test indicates that the cluster frequency is lower than the field frequency at the 99.4 percent and 98.6 percent confidence levels for two field samples. Several systematic effects that may have influenced this result are investigated. It is possible that systematic effects may account for the apparent deficiency, but further work is required to show this. There is an indication that the frequency of Ap stars may increase with age, but this result is not statistically significant. Some Ap stars appear in peculiar positions in the cluster color-magnitude diagram, probably because of the effect on their color of flux redistribution caused by the peculiar abundances. The frequency of Am stars in galactic clusters appears to be normal compared with the field. The frequency of Am stars appears to increase with cluster age. A 2 test indicates this increase is significant at the 96.5 percent confidence level. Subject headings: clusters: open - stars: evolution - stars: metallic-line - stars: peculiar A - stars: stellar statistics Publication: The Astrophysical Journal Pub Date: May 1976 DOI: 10.1086/154337 Bibcode: 1976ApJ...205..807H full text sources ADS | data products SIMBAD (264)