UBVJHK synthetic photometry of Galactic O stars

¹ Max-Planck Institut fr Extraterrestrische Physik, Postfach-1312, 85741 Garching, Germany e-mail: martins@mpe.mpg.de
² GRAAL, CNRS UMR 5024, Université Montpellier II, 34095 Montpellier Cedex 5, France e-mail: bertrand.plez@graal.univ-montp2.fr

Received: 2 June 2006
Accepted: 14 June 2006

Abstract

Aims.The development of powerful infrared observational techniques enables the study of very extincted objects and young embedded star-forming regions. This is especially interesting in the context of massive stars that form and spend a non negligible fraction of their life still enshrouded in their parental molecular cloud. Spectrophotometric calibrations are thus necessary to constrain the physical properties of heavily extincted objects.

Methods.Here, we derive UBVJHK magnitudes and bolometric corrections from a grid of atmosphere models for O stars. Bessel passbands are used. Bolometric corrections (BC) are derived as a function of and are subsequently used to derive -spectral type (ST) and absolute magnitudes- relations.

Results.Infrared magnitudes and, for the first time, bolometric corrections are given for the full range of spectral types and luminosity classes. Infrared colors are essentially constant, and is 0.05 mag bluer than previously proposed. Optical calibrations are also provided and are similar to previous work, except for which is found to be at minimum -0.28 for standard O stars, slightly higher (0.04 mag) than commonly accepted.

Conclusions.We present a consistent set of photometric calibrations of optical and infrared magnitudes and bolometric corrections for Galactic O stars as a function of and spectral type based on non-LTE atmosphere models including winds and line-blanketing.