Relation between the temperature and the median value of Hα for each star. Colours are given according to log RHK value sources: values from the literature are plotted in red, while for the blue dots the values are derived from X-ray luminosity. The blue triangles indicate that the value for a star is only an upper limit. Green diamonds indicate the bright stars sample. Open symbols correspond to quiet stars. The line only shows the fit of the binaries to have a sample unbiased by activity. The line shows the best fit for the quiet stars. The position of the Sun is also shown with ⊙.
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