Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1988
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988a%26a...195..208l&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 195, no. 1-2, April 1988, p. 208-213. Research supported by the Northern Irela
Astronomy and Astrophysics
Astrophysics
34
Abundance, B Stars, Early Stars, Helium, Star Clusters, Stellar Spectrophotometry, Least Squares Method, Polynomials, Stellar Temperature
Scientific paper
From narrow-band photometry of B-type stars, Nissen (1974, 1976) concluded that helium was underabundant by a factor of approximately 1.7 in the young cluster h and Chi Per, a conclusion subsequently supported by Wolff and Heasley (1985). Here, high-resolution spectra of a subset of Nissen's sample of cluster stars are presented, and LTE model atmosphere analyses performed to derive helium abundnces from the lines at 4009, 4026, 4121, 4143, 4437 and 4471 A. One star (Oosterhoff 2232) was found to be a double-lined spectroscopic binary, while the other five have a normal mean helium abundance of 10.92 + or - 0.05. The principal reason for the disagreement between the helium abundance is the difference in the adopted surface gravities, deduced by Nissen from the Stromgren beta index and, in this work, from profile fitting the H-delta and H-epsilon lines. The latter method leads to values systematically lower by approximately 0.3 dex. The uncertainties associated with deriving gravities from the index are briefly discussed.
Brown Paul J. F.
Dufton Philip L.
Lennon Daniel J.
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