Formation of neutral disk-like zone around the active hot stars in   symbiotic binaries
  In this contribution we present the ionization structure in the enhanced wind from the hot star in symbiotic binaries during active phases. Rotation of the hot star leads to the compression of the outflowing material towards its equatorial plane. As a result a neutral disk-like zone around the active hot star near the orbital plane is created. We modelled the compression of the wind using the wind compression model. Further, we calculated the neutral disk-like zone in the enhanced wind from the hot star using the equation of the photoionization equilibrium. The presence of such neutral disk-like zones was also suggested on the basis of the modelling the spectral energy distribution of symbiotic binaries. We confront the calculated ionization structures in the enhanced wind from the hot star with the observations. We found that the calculated column density of the neutral hydrogen atoms in the neutral disk-like zone and the emission measure of the ionized part of the wind from the hot star are in a good agreement with quantities derived from observations during active phases. The presence of such neutral disk-like zones is transient, being connected with the active phases of symbiotic binaries. During quiescent phases, such neutral disk-like zones cannot be created, because of insufficient mass loss rate of the hot star. 
Zuzana Carikova and Augustin Skopal
astro-ph.SR