Intense X-ray flares from active stellar systems : EV Lacertae and HD8357.

X-ray light curves (0.5 - 20 keV), each approximately 1 week in duration, are presented for the dMe flare star, EV Lac, and the RS CVn binary system, HD 8357, based on data obtained with the A-1 Sky Survey experiment on HEAO 1. Four flares in all were seen, two from EV Lac and two from HD 8357. Variable low-level quiescent emission was also observed from both objects. These light curves represent the first unambiguous observations of more than one flare plus intervening quiescent X-ray emission from active stellar systems. Estimates of time averaged X-ray flaring luminosities show that for at least some epochs, up to an order of magnitude more energy is expended in X-ray flaring than in optical flaring.