Outer atmospheres of cool stars. XV. High-dispersion ultraviolet studies of active chromospheric G-K dwarfs.

Abstract

The authors have obtained IUE ultraviolet echelle spectra of the three late-type active-chromosphere dwarf stars χ¹ Ori, ξ Boo A and ɛ Eri. These are compared with previously published observations of the quiet chromosphere dwarfs α Cen A and α Cen B. The spectra indicate a gross strengthening of chromospheric and transition-region line fluxes from quiet to active dwarf stars without a fundamental change in the line shapes. Qualitatively the same spectroscopic behavior is seen in detail on the solar surface between regions of strong and weak magnetic fields. They believe that the correspondence between the stellar and solar behavior is not accidental, but instead affirms that enhanced chromospheric and coronal emission on late-type main sequence stars is a result of increased surface coverage of magnetic active regions.