Distribution histogram of η₁ values calculated from the RV of template matching. For convenience of plotting, values greater than 20 are capped at 20. In this distribution, about 13.5% of the sources have η₁ > 2.5. Considering the theoretical prediction of DWDs accounting for around 10% in the Milky Way (Maxted & Marsh 1999; Maoz & Hallakoun 2017; Napiwotzki et al. 2020; Korol et al. 2022; O’Brien et al. 2024; Munday et al. 2024) and the need for further selection, η₁ > 2.5 is a loose but reliable criterion.