Evolutionary status and magnetic activity distribution of sample stars. Left: colour-magnitude diagram of sample stars compared with the PARSEC isochrones (Bressan et al. 2012) projected into the Gaia eDR3 photometric system (Evans et al. 2018). Right: mean ⟨$R_{\mathrm{H}\mathrm{K}}^{\mathrm{\prime }}$⟩ index distribution of sample stars. The grey areas represent the ± 1σ envelopes of 1000 realisations of the $R_{\mathrm{H}\mathrm{K}}^{\mathrm{\prime }}$ index distribution assuming a Gaussian distribution of the average ⟨$R_{\mathrm{H}\mathrm{K}}^{\mathrm{\prime }}$⟩ index of each star around the value provided in the AMBRE-HARPS catalogue of $R_{\mathrm{H}\mathrm{K}}^{\mathrm{\prime }}$ indices with the uncertainty given in the catalogue.