Optical spectrum of Cyg OB2 No. 12

We have identified about 200 spectral features at 4552-7939{AA}, including interstellar NaI, KI and numerous DIBs, which are in the strongest absorptions in the spectrum, along with the HeI, CII, SiII lines. A two-dimensional spectral classification indicates that the star's spectral type is B5+/-0.5 Ia^+^.

Our analyses of the radial velocities pattern shows the presence of a radial velocity gradient in the stellar atmosphere due to the infall of matter onto the star. The strong H(alpha) emission line displays broad Thompson wings and time-variable core absorption, providing evidence that the stellar wind is inhomogeneous and slightly blue-shifted P Cygni absorption profile. We conclude that the wind is time-variable.