Kovtyukh V. Physical and chemical characteristics of the pulsating supergiants and non-variable late-type stars and distribution of the metallicity in the observable part of the Galactic disc.

The thesis reports the results of the spectroscopic investigation of the Main Sequence (MS) stars, giant stars, non-variable supergiants, classical cepheids and virginides of spectral classes F, G, K that are published in 64 papers. Using the line-depth ratios technique, the programs for determination of the effective temperatures for the MS stars, giant stars and supergiant stars (spectral classes F-K, internal precision 5-25 K) were elaborated. A new gap in the distribution of stars within the MS in the temperature range 5560 to 5610 K was discovered. Thesis presents the results of a detailed multiphase spectroscopic analysis of many classical cepheids. We discovered the first lithium-rich cepheids in the Galaxy. We suggest that the observed features on the line profiles in the spectra of X Sgr, V1334 Cyg, EV Sct, and BG Cru can be caused by the non-radial oscillations. Reddenings of 74 F, G, K supergiants and 164 classical cepheids based on spectroscopic data were derived. Using 380 high-resolutionspectra of 190 galactic cepheids, the radial elemental distribution in the galactic disc between galactocentric distances in the range 4-16 kpc were investigated.