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Issue A&A Volume 382, Number 3, February II 2002 Page(s) 999 - 1004 Section Formation, structure and evolution of stars DOI 10.1051/0004-6361:20011703

A&A 382, 999-1004 (2002)
DOI: 10.1051/0004-6361:20011703

On the effective temperature scale of O stars

F. Martins¹, D. Schaerer¹ and D. J. Hillier<sup>2

1</sup>  Observatoire Midi-Pyrénées, Laboratoire d'Astrophysique, 14 Av. E. Belin, 31400 Toulouse, France
²  Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA

(Received 18 September 2001 / Accepted 16 November 2001 )

Abstract
We rediscuss the temperature of O dwarfs based on new non-LTE line blanketed atmosphere models including stellar winds computed with the CMFGEN code of Hillier & Miller (1998). Compared to the latest calibration of Vacca et al. (1996), the inclusion of line blanketing leads to lower effective temperatures, typically by ~4000 to 1500 K for O3 to O9.5 dwarf stars. The dependence of the T_eff-scale on stellar and model parameters - such as mass loss, microturbulence, and metallicity - is explored, and model predictions are compared to optical observations of O stars. Even for an SMC metallicity we find a non-negligible effect of line blanketing on the T_eff-scale. The temperature reduction implies downward revisions of luminosities by ~0.1 dex and Lyman continuum fluxes Q₀ by approximately 40% for dwarfs of a given spectral type.

Key words: stars: general -- stars: temperature -- stars: fundamental parameters -- stars: atmospheres

Offprint request: F. Martins, martins@ast.obs-mip.fr

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