Radiative Transfer in Astronomical Masers. I. The Linear Maser
Abstract
A comprehensive, unified approach to radiative transfer in astronomical maser sources is presented. A general formalism and detailed analytic solutions are given for the linear maser, including the case of a source illuminated by background radiation. A new, general expression is presented for the product of intensities of the two streams on any given ray. The complete analytic solution of a linear maser without background radiation is developed, and the results of the numerical calculations of Alcock and Ross (1985) are explained. A detailed solution is presented of a threedimensional maser of an arbitrary shape. This general solution is then expressed in terms of the escape probability approach, providing for the first time a rigorous, formal foundation for the employment of this useful method in numerical solutions of the level populations of a maser system. The general solution is applied to the spherical geometry, discussing the observational implications.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 1990
 DOI:
 10.1086/169372
 Bibcode:
 1990ApJ...363..628E
 Keywords:

 Interstellar Masers;
 Radiative Transfer;
 Background Radiation;
 Computational Astrophysics;
 Maser Outputs;
 Astrophysics;
 MASERS;
 RADIATIVE TRANSFER