Stellar XUV Spectra from Coronal Loop Models

Following the analogy with the solar corona, we describe the observed EUV and X-ray emission from late-type stars as originating from optically thin plasma magnetically confined in closed loops, according to the model by Serio et al. (1981). This model takes into account optically thin radiative losses, thermal conduction, and heating terms in the energy balance equation, as well as gravity in the hydrostatic equilibrium equation, thus providing a description physically more appropriate than that obtained by simple one- or two-temperature thermal models. We generate loop models with a variety of characteristic parameters (such as loop base pressure, loop length, or stellar surface gravity), to synthesize XUV spectra from the emission measure vs. temperature model distribution, and to fold them through the relevant instrumental response, in order to allow a direct comparison with observational data. In this paper, we show some examples of this approach pertaining to ROSAT and EUVE data.