Discovery of quiescent X-ray emission from HR1099 and RS CVn [6]

OBSERVATIONS with the HEAO 1 satellite have shown that RS CVn binary systems represent a new class of soft X-ray sources¹. While the space density of the normal period RS CVn systems is large⁹, only 26 are known optically¹⁰ and, because of their low X-ray luminosity, only about nine of these should be observable from HEAO 1. We present here our discovery of X-ray emission from HR1099 (ref. 2) and the prototype member of this class, RS CVn itself. We also comment on the possible nature of the X-ray emission mechanism in these systems.