The Interaction of X-Ray Sources with Optically Thin Environments

The physical conditions in an optically thin gas surrounding a source of X-rays are calculated for various combinations of parameters characterizing the source and the gas. The source of luminosity L is assumed to emit its radiation in the form of thermal bremsstrahlung at a temperature T~, and the gas density N is assumed to be constant and low enough so that all ions, except those having metastable states, are in their ground states. The electron temperature and the ionization equilibrium of hydrogen, helium, carbon, nitrogen, oxygen, and neon are plotted as a function of the parameter L/Nr2 (r is the distance from the source) for T~ equal to 1, 10, and 100 million degrees The coefficient for absorption of X-rays of various energies is calculated as a function of electron temperature for a gas excited by brems- strahiung radiation, and for a gas whose equilibrium is established purely by collisions The results are briefly applied to problems in X-ray astronomy