A fine analysis of the helium-rich star HD 184927.
Summary. An LTE fine analysis of the helium-rich star HD 184927 has been performed by using a grid of flux-constant model atmospheres. Observational material includes both high (6.5 A/mm) and moderate dispersion spectrograms covering the spectral region 3600 A- 6200 A and moderate resolution spectral scans. The final model has been adopted to match the following criteria: (1) equal hydrogen abundance from both the hydrogen and helium equivalent widths, (2) ionization equilibria of Si `i/Si iii and S u/S iii, (3) Hy and H profiles, (4) Hel, 4471, 4388, 4143 profiles, and (5) the continuous flux distribution (Balmer discontinuity). A micro-turbulent velocity has been determined from the metallic lines. This model is parameterized by The metal abundances are approximately normal, except for S, Ar, and Fe which may be slightly overabundant. Mass, radius, luminosity, and distance are determined to be = , =7.3 , log(L/L0)=4.l, and r = 1260 pc. These values of mass, radius, and luminosity are typical for helium-rich, or hydrogen-deficient, stars of which a Ori E may be called a prototype. Key words: helium-rich stars - fine analysis - abundance determination - physical parameters Teff = 22500 0K He =0.50 logg=3.80 v =6km/s
Astronomy and Astrophysics
- Pub Date:
- July 1974