A Short Characteristic Solution for the 2.5D Transfer Equation in the Envelopes of O and B Stars

We discuss work toward developing a 2.5D non-LTE radiative transfer code. Our code uses the short characteristic method with modifications to handle realistic 3D wind velocities. We also designed this code for parallel computing facilities by representing the characteristics with an impact parameter vector p. This makes the interpolation in the radiation angles unnecessary and allows for an independent calculation for characteristics represented by different p vectors. The effects of the velocity field are allowed for by increasing, as needed, the number of grid points along a short characteristic. This allows us to accurately map the variation of the opacities and emissivities as a function of frequency and spatial coordinates. In the future we plan to use this transfer code with a 2D non-LTE stellar atmosphere program to self-consistently solve for level populations, the radiation field and temperature structure for stars with winds and without spherical symmetry.