All Figures

	Figure 1: Evolution of the chromospheric activity of HD 81809 in the Mt. Wilson S index data, from 1966 to the end of 2002 (see Baliunas et al. 1995, for details, data courtesy of S. Baliunas).
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In the text

Figure 2: Evolution of the mean (averaged over the duration of each XMM- Newton observation, each spanning a few hours) X-ray luminosity in the 0.2-2.5 keV (ROSAT) band (squares, right hand scale) of HD 81809 from April 2001 to May 2007 together with the chromospheric Ca   II activity measured by the SSS at Lowell (crosses, left hand scale). For the X-ray data points taken in 2004-2007 the uncertainty on the X-ray luminosity is smaller than the symbol size.

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In the text

	Figure 3: Evolution of the X-ray surface flux (in the 0.2-2.5 keV band) of HD 81809 from April 2001 to May 2007. The typical X-ray surface flux of the Sun at minimum and maximum of the cycle, in the ROSAT band, is also plotted.
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In the text

Figure 4: The evolution of the coronal X-ray temperature and luminosity along the cycle in both the Sun (crosses, data adapted from Orlando et al. 2001) and HD 81809 (triangles). The figure also shows the synthetic values for HD 81809 obtained assuming a different coverage of AR and CO (squares); the crossed square marks the synthetic values for HD 81809 considering the contribution of a very intense flare (GOES class X9) to the non-flaring corona at the maximum of the cycle.

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In the text

	Figure 5: The modeled emission measure vs. temperature distributions for HD 81809 at cycle maximum (solid histogram) and minimum (dotted histogram). The shaded area marks the contribution from AR.
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In the text