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Helium abundance in atmospheres of stars appearing in OB associations and young clusters
An improved version of Liubimkov's (1974) method is used to determinethe relative helium abundance, N(He)/N(H), in the atmospheres of 80stars of spectral types O6.5 to B2 belonging to OB associations andyoung clusters. Specific results are presented for Mon OB1 and OB2, CepOB2 and OB3, Sco OB2, Lac OB1, Ori OB1, and Cas OB6. It is shown thatthe mean value of N(He)/N(H) increases with increasing stellar age andincreasing cluster or association size. A relative helium abundance of0.09 to 0.10 is found to be appropriate for stars that are severalmillion years old, and a relative abundance of 0.13 is obtained forstars older than 10 million years. It is noted that the latter value isalso characteristic of hot field stars.
| A Spectroscopic and Photometric Investigation of the Association Cepheus OB2
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...154..923S&db_key=AST
| Determination of size, color indices, and spectral classes of stars in an area centered on R.A.=21h24m, Dec=+58.5deg.
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Member of following groups:
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Observation and Astrometry data
| Constellation: | Céphée |
| Right ascension: | 21h10m57.66s |
| Declination: | +60°13'16.3" |
| Apparent magnitude: | 9.309 |
| Proper motion RA: | -1.3 |
| Proper motion Dec: | -5.3 |
| B-T magnitude: | 9.58 |
| V-T magnitude: | 9.332 |
Catalogs and designations:
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