Evolution of the chromospheric and coronal activity of intermediate mass stars

Recent ultraviolet and X-ray observations pertaining to the outer atmospheric structure of intermediate mass (4-6 solar masses) stars and the evolution of their structure are presented. A distance-limited (d equal to or less than 200 pc) IUE ultraviolet survey of early K bright giants shows that C IV emission commonly is present. These stars are almost evenly split between stars showing hybrid-chromospheric and coronal outer atmospheric structures. Exosat observations have been obtained for three hybrid stars, of which only Alpha TrA, the nearest, is detected. The temperature of the emitting plasma is likely to be about 10 to the 6th K. Observtions of six K II stars made with the Einstein satellite show no detections. The general conclusion from the available X-ray data is that early K bright giants are not strong X-ray sources.