The ubiquity of carbon dredge-up in hydrogen-deficient white dwarfs as revealed by GALEX

The convective dredge-up of carbon from the interiors hydrogen-deficient white dwarfs has long been invoked to explain presence absorption features in spectra cool DQ stars ($T_{\rm eff} < 10{,}000\,{\rm K}$). It hypothesized that this transport process is not limited and also operates, albeit less efficiently, non-DQ within same temperature range. This population predominantly composed DC dwarfs, which exhibit featureless optical spectra. However, no direct observational evidence ubiquitous pollution thus far uncovered. In Letter, we analyze data Galaxy Evolution Explorer (GALEX) reveal photometric signature ultraviolet lines most $8500\,{\rm K} \leq T_{\rm 10{,}500\,{\rm K}$ Our results show vast majority experience at some point their evolution.