Discrete X-ray sources—a theoretical appraisal

Abstract

X-ray and γ -ray astronomy is in its infancy. Parallels in its development with the early history of radio astronomy have often been drawn. In this paper I attempt to unravel the theoretical questions which have been raised by the discovery of the discrete sources. To do this we divide the discussion up into three sections: (1) galactic sources, (2) extragalactic sources; (3) possible discrete sources of γ -rays.