On the sensitivity of HeI singlet lines to the FeIV model atom in O stars
arXiv:astro-ph/0605211 · doi:10.1051/0004-6361:20054489
Abstract
Recent calculations and analyses of O star spectra have revealed discrepancies between theory and observations, and between different theoretical calculations, for the strength of optical HeI singlet transitions.We investigate the source of these discrepancies. Using a non-LTE radiative transfer code we have undertaken detailed test calculations for a range of O star properties. Our principal test model has parameters similar to those of the O9V star, 10 Lac. We show that the discrepancies arise from uncertainties in the radiation field in the HeI resonance transition near 584Angs. The radiation field at 584Angs. is influenced by model assumptions, such as the treatment of line-blanketing and the adopted turbulent velocity, and by the FeIV atomic data. It isshown that two FeIV transitions near 584Angs can have a substantial influence on the strength of the HeI singlet transitions. Because of the difficulty of modeling the HeI singlet lines, particularly in stars with solar metalicity, the HeI triplet lines should be preferred in spectral analyses. These lines are much less sensitive to model assumptions.
7 pages, 9 figures, accepted for publication in A&A
Cited by in corpus (8)
- A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
- Stellar and wind properties of massive stars in the central parsec of the Galaxy
- Bright OB stars in the Galaxy IV. Stellar and wind parameters of early to late B supergiants
- Statistical properties of a sample of periodically variable B-type supergiants - Evidence for opacity-driven gravity-mode oscillations
- Hydrogen and helium line formation in OB dwarfs and giants. A hybrid non-LTE approach
- The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. III. More Results from the Magellanic Clouds
- The ionizing radiation from massive stars and its impact on HII regions: results from modern model atmospheres
- Central stars of planetary nebulae in the Galactic bulge