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Spectral Microvariability and a structure of winds of hot stars

The project of studing the fast line profile microvariability (LPmV) has started in 2001. In our paradigm the microvariability means that line profiles have a very weak variations with the amplitude about of 1% in units of the continuum adjacent to the line.

This means that we need the spectra of a very good quality with the signal to noise ratio S/N>200. It is why, we selected bright (V<6m) . northern O and early B stars whose spectra could be obtained with the parameters required to look for variability at the using the CEGS echelle spectrograph, maintained at the coude focus of the 1-m Northern Caucasus Special Astrophysical Observatory (SAO) telescope (Musaev 1996). The list of the program stars includes 29 obiects.

When choosing appropriate dates of observations, the program stars can be observed for almost the entire night. As a result, long series of observations (spanning two or three stellar rotation periods) needed for an accurate separation of the regular line-profile variability component can be obtained when they are observed for three to six nights. We suggest the following strategy for observations: obtaining long series of observations with the 1-m SAO telescope in order to reveal the overall pattern of variability in the program stars, and studying in detail those stars in which profile variability or any unusual spectral features were detected using the 1.8-m telescope of the Bohinsan astronomical observatory (BOAO) in the South Korea or 6-m SAO telescope.

To the present day we have obtained more than 1200 spectra of 12 of the program stars with using 1-m and 6-m SAO telescopes, 6-m SAO telescope and the 1.8-m telescope of the BOAO. The position of all observed stars on the HR diagram can be found here. Part of the program stars was observed with the Zeeman analyzer at the SAO 1-m telescope for trying to detect magnetic fields of O and early B stars.