Model atmosphere analysis of the A3 Ia - O supergiant HD 33579 in the Large Magellanic Cloud.
Abstract
Summary. A fine analysis of HD 33579, an A3Ia-O supergiant in the Large Magellanic Cloud, has been done by evaluating 4 high dispersion spectra(12.3A/mm) taken at the European Southern Observatory. The Observations are best fitted by a model atmosphere (radiative equilibrium, LTE, no line blanketing) with the parameters Te =81300 and log g =0.7 and a micro- turbulence varying with the optical depth from 6 km/s at T =2.0-26 km/s in the outermost layers. The computed continuum agrees reasonably with photoelectric measurements. The computed and observed colour indices (corrected for interstellar absorpilon) are (U - B)cai = -0.29,(U- B)obs = -0.28,(B V)cai= + 0.13, (B- V)obs = +0.14. The bolometric correction is B.C. =0.06. The profiles of the absorption lines are asymmetric, which can be interpreted by a depth dependent radial large scale motion. A strong H -emission can be explained by a chromospheric shell, which is moving with a velocity up to 170 km/s relative to the photosphere. The average metal abundance is practically same as for the sun (loge - +0.12). We have computed the luminosity as L/ , the radius as R/ and the mass as / 25. Key words: fine analysis - model atmospheres - abundance determination - supergiant - Large Migeilanic Cloud
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1972
- Bibcode:
- 1972A&A....20..275W