Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aas...193.9908g&link_type=abstract
American Astronomical Society, 193rd AAS Meeting, #99.08; Bulletin of the American Astronomical Society, Vol. 30, p.1396
Astronomy and Astrophysics
Astronomy
Scientific paper
Luminous Blue Variables (LBVs) have recently been recognized as keys to the evolution of massive stars; understanding the physical mechanisms causing their changing spectral type and huge mass loss rates are thus of great importance. We have obtained two data sets of high resolution optical spectra to address the following questions: \begin{enumerate} which physical mechanisms are responsible for the observed spectral variability? do LBV winds have inhomogeneities and/or substructures? For the first question we have obtained high resolution spectra (R~ 60 000, lambda ~3600--7000 Angstroms) of a sample of 20 LBVs and LBV-candidates in the Milky Way and the Magellanic Clouds. Substructures have been detected in almost all our observed objects suggesting that inhomogeneities exist in the wind of at least some LBVs. To address the second question we have observed the galactic LBV HD 160529 over 4 years to study the variability of its optical spectrum. We found that all spectral lines are variable. The lines with P Cygni-type profiles show variations in the emission as well as in the absorption components. Even pure absorption lines, forming deep in the atmosphere (e.g. He I lambda5876 and Mg II lambda4481 ), show signs of wind-influence, indicating that the observed variations are caused at the very base of the wind (e.g. by propagating density fluctuations starting at the photosphere). The results from the analyzes of this data with static NLTE-codes (Hubeny et al.: TLUSTY, SYNSPEC) and with dynamical and pulsational models (Rivinius et al.: SEIDYNAMIC; Kaufer et al.: Monte Carlo code) will be discussed in the paper presentation.
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