Non-stationary processes in supergiant stars of spectral class B and A
In this report we have presented the results of spectral observations of the supergiant stars HD 187982 (Sp. A1 Iab) for 2016-2021, HD 208501 (Sp. B8 Ib) for 2013-2021, and HD190603 (Sp. B1.5 Ia) for 2010-2021. Spectral observations was made at 2 m telescope of Shamakhy Astrophysical observatory by using a fibre echelle spectrograph ShAFES. In spectral range λ3700-9000Å, with spectral resolution R=28000 and R=56000.
1. HD 187982 (Sp. A1 Iab). Spectrophotometrical parameters: equivalent widths EW, central depth Rλ, radial velocities RV of the lines Hα-Hε, HeI 5876, D NaI, Si II λ6347, 6371Å for all data was determined. Our measurements for 2017 data showed that measure of variability for hydrogen lines higher than the other spectral lines.
2. HD 208501 (Sp. B8 Ib). The profiles, radial velocities and equivalent widths of Hα, Hβ, HeI and doublet NaID lines in the spectrum of the HD208501supergiant star variation at intervals of one week or shorter time intervals. Also, a unique observation fact was revealed such as the weakening of the Hα linear profile to the level of a continuous spectrum, its formation and disappearance at full emission and full absorption. The study found that the radial velocity of the absorption component of the Hα line profile, the values of the radial velocities of the Hβ and doublet NaID lines varies in the antiphase, and the radial velocity of the HeI line at certain time intervals changes synchronous or in the antiphase with the radial velocities of the NaID, Hα, and Hβ lines. The results of observations prove that around the HD208501 star exists a disc-like gas envelope of non-uniform density that rotates at a certain angle. It is assumed that these changes are due to the pulsating of the star and the interaction of the star with the circumstellar envelope.
3. HD190603 (Sp. B1.5 Ia). The shape, radial velocity and equivalent width of the Hα and Hβ line profiles in the spectrum of the supergiant star HD190603 vary with time. The Hα line profile consists of an absorption and an emission component. The emission component, depending on time, consists of one, two or three components. The absorption and emission components radial velocity and equivalent width of the Hα and Hβ line vary in time with a period approximately of 100 - 120 days.