Doppler mapping of CP-star surfaces with weak and strong magnetic fields [chapter]

V. L. Khokhlova
The Sun and Cool Stars: activity, magnetism, dynamos  
A code for Doppler mapping of the distribution of chemical elements on stellar surfaces (Goncharskij et al, 1977 (Goncharskij et al, , 1982 has been used during the past decade to make maps for several CP-stars. The code is based on Tikhonov's method of solution of so-called ill-posed inverse problems and on an analytical expression of local line profiles in the form of the Milne-Eddington solution of the radiative transfer equation. This code takes into account the atmospheric model of the
more » ... ic model of the star through an assumed central depth of very strong and saturated lines, and through limb-darkening coefficients. As a solution one gets local line profiles and hence local equivalent widths. Recently some more sophisticated codes were developed by Piskunov (1985) and Vogt et al. (1987) which use the results of the numerical solution of the transfer equation directly for local profiles and are thus able accurately to take into account an appropriate atmospheric model. In these codes the results of solution are local abundances of an element. Only Piskunov's code provides a simultaneous solution for all Stoke's parameters (
doi:10.1007/3-540-53955-7_154 fatcat:zh3b4yueznaypi4hnl3tuk6sma