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A. K. Dupree (Smithsonian Astrophysical Observatory/CfA), J. Sanz-Forcada (INAF Osservatorio Astronomica di Palermo and ESA)
The Helium I 10830 Angström line has been surveyed at high resolution in the spectra of cool stars. Since the lower level of the transition is generally populated by recombination from He II following photoionization, its strength offers an insightful tool for the presence of coronal radiation. Additionally, because the line-forming process is independent of local conditions, the line profile can also probe atmospheric dynamics. We have used the SOFIN spectrograph on the Nordic Optical Telescope with high resolution (R ~ 100,000) and good signal-to-noise to survey active cool stars (both binary and single stars) in the He I line. In addition, the extreme ultraviolet flux for the same objects measured directly with the Extreme Ultraviolet Explorer satellite makes possible an empirical determination of the dependence of the helium line strength on the coronal radiation field of the star. This dependence differs between active dwarf and giant stars. Signs of mass motions are also found in some objects.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.