Left: L_X/L against L of the our best fitting models (dark blue diamonds with 2σ error bars). Right: Distribution of the L_X/L values from our best fitting models. We indicate the typical observed value of L_X/L (orange dashed line) and the typical scatter around this value (yellow band). We stress that the X-ray luminosity L_X/L is not a free parameter in our fitting and the L_X/L values shown here do not represent the actual X-ray flux of the given stars: this plot serves solely as a check on our assumptions (see text).