Max-Planck Institut für Astrophysik,
In this paper we describe the status of the continuing effort to
construct realistic models for expanding atmospheres (e.g.,radiation
driven winds of hot stars, SNIa, and novae). The potential of our
theoretical concept is demonstrated by an application to the O3Iaf star
HD 93129A. We present our method of O-star diagnostics, which is based
on a comparison of calculated synthetic high-resolution spectra
covering the observable UV region with observed spectra. As a result
we get physical constraints on the properties of stellar winds, and the
stellar parameters and abundances can be determined.
Observed Copernicus (900-1500Å; Morton & Underhill 1977)
and IUE (1500-1800Å; Walborn et al. 1985)
high-resolution UV spectrum of the O4I(f) star Puppis.
The most important strong and weak winds lines are identified and marked.
The large number of wind contaminated FeVlines
between 1250 and 1500Å is striking.
(From Pauldrach et al. 1994b).
Comparison of observed and calculated synthetic
spectrum of the O3If* star HD 93129A.
The upper two panels show the ORFEUS spectrum, where
the interstellar molecular lines
of H2 and HD are included in the spectrum fit. The lower three panels
show the usual IUE spectrum where the narrow sharp interstellar lines are
not included in the spectral fit (from Taresch et al. 1997).
Although such models already reproduce the observed quantities
satisfactorily the method is still affected by shortcomings. Special
emphasis is therefore given to the latest improvements which involve a
fundamental step towards a realistic description of stationary wind
models. These improvements comprise the use of accurate atomic data
for a very detailed multilevel non-LTE treatment of the metal ions, the
revised inclusion of EUV and X-ray radiation by shock-heated matter,
and, most importantly, the consistent calculation of line blocking
and blanketing. With the solution of the latter problem the
astrophysically important information about the ionizing fluxes of
O stars is obtained as a by-product.
stars: atmospheres, early-type, mass-loss, blanketing, X-rays