1999ApJS..122..269D

Over half of the sources detected in the Extreme-Ultraviolet Explorer (EUVE) All-Sky Survey and Deep Survey (50-760 Å) that have known optical counterparts are late-type stars. The EUV emission from late-type stars is thought to originate from hot, collisionally dominated, optically thin plasmas, with temperatures ranging between 10⁵ and 10⁸ K, that are confined by magnetic structures analogous to those observed on the Sun. The different filters providing wavelength discrimination used on the EUVE scanning telescopes are sensitive to emission from optically thin plasmas with temperatures throughout this range. We have investigated the responses of each of the EUVE photometric instruments as a function of plasma temperature for different interstellar medium column densities. The results will be of use for interpreting EUVE photometric count rates for astrophysical collisionally dominated, optically thin plasma sources. The different sources of uncertainty entering into these types of calculation are reviewed. Three issues of special importance not generally considered in the interpretation of EUV observations of radiative loss are emphasized: (1) current radiative loss models are incomplete in their treatment of ionization states with n=2 and n=3 ground states; (2) the interstellar medium neutral and ionized He absorbing columns are generally unknown and represent potentially large uncertainties in the interpretation of EUV photometry; and (3) plasma chemical composition has a large influence on the shape of radiative loss curves, photometric flux calibrations, and derived emission measures.