Unified NLTE Model Atmospheres Including Spherical Extension and Stellar Winds - Part Four - Improved Line Transfer and Wind Contamination of H he Profiles

Details Unified NLTE Model Atmospheres Including Spherical Extension and Stellar Winds - Part Four - Improved Line Transfer and Wind Contamination of H he Profiles Unified NLTE Model Atmospheres Including Spherical Extension and Stellar Winds - Part Four - Improved Line Transfer and Wind Contamination of H he Profiles

Jun 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...273..533s&link_type=abstract

Astronomy and Astrophysics, Vol.273, NO. 2/JUNII, P. 533, 1993

Astronomy and Astrophysics

Astrophysics

40

Stars: Atmospheres, Line Formation, Stars: Early Type, Stars: Emission Lines, Stars: Mass Loss

Scientific paper

The treatment of NLTE multilevel radiative transfer in the presence of sub- and supersonic velocity fields of unified model atmospheres is discussed. The solution of the line transfer in the comoving frame is obtained via Accelerated Λ-Iteration where we apply the new Approximate Λ-Operator developed by Puls (1991). This method yields excellent convergence also in cases of very complex model atoms, where many strong, intermediate and weak lines have to be treated simultaneously and where other operators failed to achieve convergence.
This algorithm is used to investigate the contamination of photo spheric hydrogen and helium absorption lines by emission of the stellar wind. It is found that in the case of early 0-supergiants close to the Eddington-limit wind contamination is significant and leads to systematic errors in the determination of stellar parameters, if purely hydrostatic, plane parallel NLTE models are used for the spectral analysis.
Additionally, a specific behavior of the mean line intensity, namely a local minimum around the sonic point, is discussed by means of a second order Sobolev Approximation accounting for curvature terms in the velocity field.

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