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Ultraviolet spectra of two late type M stars R Aql and W Hya were obtained with the International Ultraviolet Explorer (IUE). Spectra were obtained of R Aql near maximum (cf>=0.21) and minimum (cf>=0.65) of the visible light curve. We find that the absolute flux intensity of the Mgn resonance doublet (2796 A, 2803 A) is essentially the same at these phases in the visible light curve. A nebular emission feature at 3133 A is detected at minimum light in R Aql that is possibly due to 0 III. Mg II emission is totally absent in W Hya, which contradicts earlier predictions that this star has an 8000 K permanent chromosphere. These results are discussed as they pertain to the formation of silicate grains in cool M giant atmospheres.


This article was originally published in Astronomy and Astrophysics, volume 92, in 1980.

Peer Reviewed



EDP Sciences



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