Stellar Winds in O and B Type Stars: Hydrogen Atmosphere

Abstract

We present the results of calculations of radiation driven stellar winds O-B stars. The equations of conservation of mass and momentum are solved self consistently with the equation of line transfer. The influence of radiation presence in the line on the outward momentum of the outer layers of the O and B type stars is investigated assuming an isothermal Hydrogen atmosphere. Lines in Lyman, Balmer Paschen, and Brackett series are used to calculate the line radiation pressure assuming 10 levels of H. We have considered realistic stars by using their observational data. In addition to the radiation pressure in the line we have taken into account the electron scattering and the continuum radiation is neglected. We employed Saha equation for estimating the ionized H atoms and Boltzmann equation for calculating the occupation numbers in different stages of excitation. We have applied a non-LTE two level-atom approximation to solve the line transfer for the purpose of calculating the radiation pressure in the line. The effects of radial velocity gradients, aberration and advection have been taken into account in the calculation of radiation pressure in the lines. We have applied this theory to several stars making use of their observationally derived temperatures, masses, radii and mass loss rates. We have derived the ionized fraction of the hydrogen atoms, electron density, the population density in different states of excitation, thermalization parameters, radial optical depths, the line radiation pressure due to combined effect of Lyman, Balmer, Paschen and Brackett lines up to 10 levels.