Emission lines in the spectrum of the red-dwarf flare star EV Lac: Modeling of the quiescent chromosphere

We present spectral observations of the red-dwarf flare star EV Lac made at the Crimean Astrophysical Observatory in 1994 and 1995, and describe a method for semi-empirical modeling of the chromospheres of red dwarfs based on their emission spectra. We have modeled the quiescent state of the chromosphere of EV Lac for the cases of a homogeneous chromosphere and of active regions covering one-half and one-third the stellar surface. All models that are consistent with the observations indicate a region with a small vertical temperature gradient, a so-called temperature plateau. The calculated structure of the stellar chromosphere is compared with that of the solar chromosphere.