Modeling of Coronal X-Ray Emission from Active Cool Stars

X-ray pulse-height spectra of the most active cool stars in the Hyades cluster obtained with the Einstein IPC cannot be modeled using isothermal thin plasma emission. Addition of a second isothermal component provides acceptable fits. However, a more physically meaningful set of coronal parameters is provided by models which consist of an ensemble of loops with a single maximum temperature, but with the temperature distribution within the loop determined by loop physics. Such models have been successfully fit to the IPC pulse-height spectra. Constraints on loop parameters are discussed for four F-G dwarfs in the Hyades.