Abstract

Validity of clumping approximations for mass-loss rates determination

Jiří Kubát (Astronomical Institute Ondřejov)

Brankica Šurlan (Astronomical Institute Ondřejov)

Clumping in stellar winds of hot stars is a possible consequence of radiative-acoustic instability appearing in solutions of radiative-hydrodynamical equations. However, clumping is usually included to stellar atmosphere modeling and radiative transfer calculations in a highly approximate way via a global free parameter called the clumping factor. Using different values of clumping factors many researchers succeeded to fit the observed spectra better and to correct observed mass loss rates. This lead to a conclusion that the stellar wind is clumped. But it is not enough to understand clumping. We critically check various methods of the treatment of clumping and their influence on the mass-loss rates in order to check their validity and to summarize current state of knowledge including highly sophisticated 3-D modeling of clumping as a necessary method to understand the real nature of the clumps.