Coronal activity in F-, G-, and K-type stars; relations between parameters characterizing stellar structures and X-ray emission |
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Authors: | CJ Schrijver R Mewe C Zwaan |
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Institution: | The Astronomical Institute, Space Research Laboratory, Beneluxlaan 21, 3527 HS Utrecht, The Netherlands |
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Abstract: | A sample of 52 stars containing dwarfs and giants is subjected to a multidimensional factor analysis. The parameters used are the soft X-ray flux at the stellar surface Fx, the Ca II H+K line-core flux FH+K, the stellar radius and mass. We find a high correlation between Fx and the Ca II H+K excess flux ΔFH+K obtained by subtracting an observational lower-limit flux from FH+K. We conclude that the lower-limit Ca II flux is uncorrelated with the stellar X-ray emission. The common-factor analysis shows that, for the present sample, Fx depends only on ΔFH+K, and not on the stellar radius or mass. All stars included in our analysis follow the relation Fx ∝ Δ1.4H+K over almost four decades in Fx. |
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