The extreme helium star BD -9 4395.
Abstract
Simultaneous optical and UV spectroscopy is used to investigate both the photospheric variations and emission-line behavior of the extreme helium star BD-9 deg 4395. The photospheric parameters of the star are rederived from the optical spectra by the method of fine analysis, on the basis of up-to-date atomic data and new line-blanketed model atmospheres. The principal results are: T(eff) = 22,700 K, log g = 2.55, n(H)/n(He) = 0.0015, and n(C)/n(He) = 0.0004. Assuming an He-shell model, a mass of about 0.7 solar mass is obtained. The emission-line spectrum which principally contains lines due to He I, C II, and Si II, is probably due to recombination in a shell, or extended atmosphere, with a temperature slightly below T(eff). Both nonvariable and variable components may be identified, and suggest substantial dynamical activity in the shell.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1992
- Bibcode:
- 1992A&A...260..133J
- Keywords:
-
- B Stars;
- Helium;
- Stellar Composition;
- Stellar Spectra;
- Ultraviolet Astronomy;
- Emission Spectra;
- Line Spectra;
- Astrophysics