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Radial Velocity Variations of the Hα and NaI D Lines for the High-Latitude Supergiant Star 89 Her

Khalilov A. M., Hajiyeva G. M., Hasanova A. R., Hasanova A. B.

Acta Astronomica

2022

Vol. 72, No. 4

297--313

The variations in the spectral parameters of the Hα and sodium doublet NaI D lines of the high-latitude supergiant 89 Her were investigated on the basis of the spectrograms obtained at the 2-m telescope of Shamakhy Astrophysical Observatory between 1975 and 2017. The research has shown that, in addition to shorter periodic changes, which were found earlier by various authors, there are also long period changes in the atmosphere of this star. It has been found that the Hα and sodium doublet NaI D line's radial velocity and the equivalent width of the absorption component vary with a period of 5000 d. The orbital elements of the binary system were determined for the first time within the spectroscopic-binary system model.

Spectroscopic Variability of the Supergiant Star HD 225094

Maharramov Y. M.

Acta Astronomica

2015

Vol. 65, No. 2

205--214

Profile variations in the Hα and Hβ lines in the spectra of the star HD 225094 are investigated using observations carried out in 2013-2014 with the 2-m telescope at the Shamakhy Astrophysical Observatory. The spectral resolution of the collected spectra is approximately 15 000. The absorption and emission components of the Hα line are found to disappear on some observational epochs. It is suggested that the observational evidence for the non-stationary atmosphere of HD 225094 can be associated in part with non-spherical stellar wind.

On the Nature of Regular Pulsation in Two LBV Stars of NGC 300

Dziembowski W. A., Sławińska J.

Acta Astronomica

2005

Vol. 55, No. 2

195--204

Two A-type supergiants in NGC 300 exhibit periodic light variations. The measured periods are 72.5 and 96.1 days. We show that the variability may be explained by the excitation of strange mode driven by the opacity mechanism acting in the layer of the iron opacity bump. The explanation requires that the two stars are significantly undermassive. In sequences of stellar models with decreasing luminosity-to-mass ratio, the unstable strange modes represent continuations of strictly aperiodic thermal modes.