A method for adding opacity distribution functions

An efficient method is presented for calculating composite opacity distribution functions (ODFs) for several opacity sources using the ODFs for each individual source. This algorithm makes it possible to change the chemical composition in the calculation of blanketed model atmospheres without recalculating the ODFs. The algorithm assumes that the strength of the opacity sources affected by the abundance change are uncorrelated in frequency with each other and with the rest of the opacity, within narrow spectral intervals. The mathematical basis of the method is introduced, the different numerical parts of the algorithm are described, and the accuracy and efficiency of the method is discussed together with some numerical examples.