Hertzsprung-Russel diagrams of our selected white dwarfs with radial velocity measurements (top panel) and the Gaia-selected common proper motion pairs (bottom panel). The cooling tracks for He-, CO-, and ONe-core white dwarfs (Althaus et al. 2013; Camisassa et al. 2016, 2019) and the isochrones are shown. The corresponding masses and ages are labeled in the top panel for clarity. The solar metallicity BaSTI isochrones with [Fe/H] = 0.06 (blue curves; Hidalgo et al. 2018) and α-enhancement (orange curves; Pietrinferni et al. 2021) are plotted at 1 and 10 Gyr (dashed and solid curves, respectively).