The outer atmosphere structure of three late type stars.

Abstract

Far ultraviolet emission lines of three late type stars, two dwarfs (chi Her and beta Com) and one subgiant (Iota Vir), have been analysed to determine the structure of their outer atmospheres. Emission line fluxes are used to find the emission measure distributions. Using three boundary values of the electron pressure, calculated in a previous paper, a sample of transition region models has been derived. The temperature gradients reach a maximum value at a certain temperature which depends only on the shape of the emission measure. The steep temperature gradient models give an impossible negative energy input at a temperature of about 10 to the 5th K. However the radiation losses exceed the net conductive fluxes at low Te.