Ultraviolet Spectroscopy of Cool Stars from IUE

Abstract

AbstractObservations of cool stars with the IUE satellite have shown that although main sequence stars have uv spectra similar to that of the sun, the spectra of the giants and supergiants are dominated by lines of neutral atoms and singly charged ions. The atmospheres of the low gravity stars are greatly extended and there is a large opacity in the stronger lines. This leads to multiple scattering and the appearance of many transitions through line ‘leakage’.A review is given of how high resolution IUE spectra have allowed line identifications to be established and some current problems are discussed.The spectroscopic diagnostic techniques for the low gravity, low density atmospheres are also briefly outlined.