Element abundance inhomogeneity in the interstellar medium based on the data of HDE 226868 (Cyg X-1) and $\alpha$ Cam

Synthetic spectrum modelling with allowance for non-LTE effects was used to determine element abundances in the atmospheres of two O-supergiants with similar physical characteristics: HDE 226868 (Cyg X-1 optical component) and $\alpha$ Cam localized at a distance of 2.5–2.7 kpc from each other. The average CNO, as well as Al, S, and Zn abundance differences are 0.15–0.30 dex. HDE 226868 has higher abundances compared to $\alpha$ Cam. The differences are in good qualitative agreement with heavy element distribution over the Galaxy disk derived by Luck et al. on the basis of 50 galactic Cepheids. This fact confirms the inhomogeneity of heavy element distribution on the scale of 2 kpc and is in agreement with the concept of preservation of the intrinsic particularities of interstellar medium “superclouds” on a time-scale of more than 1 Gyr.