Non-LTE analysis of massive O-stars. II. The O4 star zeta Puppis
Abstract
A non-LTE analysis of the O4f-star ζ Puppis is carried out using low noise coudé spectrograms. The detailed fit of the photospheric hydrogen and helium spectrum reveals:
1.The "spectroscopic" effective temperature is significantly lower than assumed previously: Teff=42000±2500 K. 2.The gravity is low: g = 1O3.5±0.15 cm s-2, which corroborates spectroscopically that ζ Puppis is further evolved from the ZAMS than early O-stars of luminosity class V. 3.Helium is slightly overabundant: NHe/(NH + NHe) =0.1410.03. 4.The final non-LTE model, which is plane parallel and in hydrostatic and radiative equilibrium, is able to reproduce the observed photospheric hydrogen and helium line profiles as well as the observed energy distribution and angular diameter. 5.The influence of the expanding envelope on the apparent angular diameter is examined by calculating the radiative transfer in spherical symmetry for Thomson-scattering in the stellar wind. For ζ Pup the correction to the angular diameter, as derived from interferometric measurements, is small. We conclude the "classical" non-LTE calculations, if carefully applied, can reproduce the hydrogen and helium line spectrum as well as the energy distribution and the angular diameter of ζ Puppis consistently.- Publication:
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Astronomy and Astrophysics
- Pub Date:
- February 1983
- Bibcode:
- 1983A&A...118..245K
- Keywords:
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- Nonequilibrium Thermodynamics;
- O Stars;
- Stellar Mass;
- Abundance;
- Diameters;
- H Lines;
- Helium;
- Stellar Envelopes;
- Astrophysics