The inhomogeneous wind of the LBV candidate CygOB2 No.12

We present the results of high-resolution spectroscopy of the extremely luminous star CygOB2 No. 12. We identified about 200 spectral features in the range 4552–7939˚A, including the interstellar Na I, KI lines and numerous very strong DIBs, along with the He I, CII, and Si II lines. An MK spectral type we derived for the object is B4.5±0.5 Ia+ . Our analysis of the radial velocity data shows the presence of a gradient in the stellar atmosphere, caused by both atmospheric expansion and matter infall onto the star. The Hα emission displays broad Thompson wings, a slightly blue-shifted P Cyg type absorption component and a time-variable core absorption. We conclude that the wind is variable in time.