 Chandrasekhar's X- and Y-function

Chandrasekhar's X-functions and Y-functions are mathematical functions that arise in the context of the study of stellar structure, particularly in the analysis of certain types of radiative properties and the behavior of radiation in stellar atmospheres. These functions were introduced by the astrophysicist Subrahmanyan Chandrasekhar in the course of his research into the transport of radiative energy in the presence of scattering.