EDP Sciences
Free Access
Volume 399, Number 2, February IV 2003
Page(s) 525 - 530
Section Stellar clusters and associations
DOI https://doi.org/10.1051/0004-6361:20021802

A&A 399, 525-530 (2003)
DOI: 10.1051/0004-6361:20021802

Non-LTE abundances of magnesium, aluminum and sulfur in OB stars near the solar circle

S. Daflon1, K. Cunha1, V. V. Smith2 and K. Butler3

1  Observatório Nacional, Rua General José Cristino 77 CEP 20921-400, Rio de Janeiro, Brazil
    e-mail: daflon@on.br;katia@on.br
2  Department of Physics, University of Texas at El Paso, El Paso, TX 79968-0515, USA
    e-mail: verne@barium.physics.utep.edu
3  Institut für Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, 81679 München, Germany
    e-mail: butler@usm.uni-muenchen.de

(Received 15 October 2002 / Accepted 29 November 2002)

Non-LTE abundances of magnesium, aluminum and sulfur are derived for a sample of 23 low- $v \sin i$ stars belonging to six northern OB associations of the Galactic disk within 1 kpc of the Sun. The abundances are obtained from the fitting of synthetic line profiles to high resolution spectra. A comparison of our results with HII region abundances indicates good agreement for sulfur while the cepheid abundances are higher. The derived abundances of Mg show good overlap with the cepheid results. The aluminum abundances for OB stars are significantly below the cepheid values. But, the OB star results show a dependence with effective temperature and need further investigation. The high Al abundances in the cepheids could be the result of mixing. A discussion of the oxygen abundance in objects near the solar circle suggests that the current mean galactic oxygen abundance in this region is 8.6-8.7 and in agreement with the recently revised oxygen abundance in the solar photosphere. Meaningful comparisons of the absolute S, Al and Mg abundances in OB stars with the Sun must await a reinvestigation of these elements with 3D hydrodynamical model atmospheres for the Sun. No abundance gradients are found within the limited range in galactocentric distances in the present study. Such variations would be expected only if there were large metallicity gradients in the disk.

Key words: stars: abundances -- stars: early-type

Offprint request: S. Daflon

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