OnH-functions of radiative transfer

Chandrasekhar'sH-functionH(z) corresponding to the dispersion functionT(z)=|_rs–frs(z)|, where [f_rs(z)] is of rank 1, is obtained in terms of a Cauchy integral whose density functionQ(x,₁,₂,...) can be approximated by approximating polynomials (uniformly converging toQ(x)) having their coefficients expressed as known functions of the parameters_r's. A closed form approximation ofH(z) to a sufficiently high degree of accuracy is then readily available by term by term integration.