A study of UV spectra of zeta Aur/VV CEP systems. VIII. Chromospheric ionization and opacity.
Abstract
Using 25 high resolution IUE spectra of Zeta Aur, 32 Cyg and 31 Cyg taken during chromospheric eclipse, the Fe I/Fe II ionization equilibrium has been determined empirically as Fe I/Fe II of about 10 exp -3.5. Fe is ionized by UV radiation from the B star companion while recombination is controlled by electrons from collisionally ionized hydrogen. An attempt is made to estimate average electron densities n(e) and temperatures T(e) consistent with both Fe I/Fe II ratios and the necessary hydrogen ionization. Typical values as taken from 32 Cygni are n(e) = about 5 x 10 to the 6th/cu cm, T(e) = about 10,500 K at h = about 5 x 10 to the 12th cm (nH = about 10 to the 9th/cu cm), with uncertainties of a factor of two for densities and about 500 K for temperatures. A density model of the inner chromosphere is derived which is in agreement with both the absorption line data and the continuum opacities which have been observed from IUE spectra near total eclipse at five selected wavelengths (i.e., from wavelength dependent eclipse) if pure Rayleigh scattering by neutral hydrogen is assumed for the continuum absorption coefficient.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1986
- Bibcode:
- 1986A&A...170...70S
- Keywords:
-
- Atmospheric Ionization;
- Chromosphere;
- Late Stars;
- Opacity;
- Supergiant Stars;
- Ultraviolet Spectra;
- B Stars;
- Density Distribution;
- Hydrogen Ions;
- Iron;
- Iue;
- Stellar Envelopes;
- Astrophysics