Estimating the total radiative power output from the hot outer layers of late-type stellar atmospheres: How many lines are required?

J.G. Doyle

The total radiative power output from the hot outer layers of six late-type stars (of different spectral types and luminosity class) is derived via an emission measure technique. This analysis was based on observational data from the spectral range 100A to 3000A obtained as a result of three separate satellite missions, i.e. Hubble Space Telescope, International Ultraviolet Explorer and the Extreme Ultraviolet Explorer. Solar observational data of active regions, coronal holes, sunspots, 'quiescent' regions and flares were also used. Based on the derived total power output from all these different plasma, it is shown that a linear relationship involving a single transition region line can be used to provide an accurate estimate of the total power output as previously shown for the Sun. The derived relationship does not include losses due to hydrogen, nor the UV continuum which can be a large contributor, particularly for very active stars.