Program: GN-2024A-Q-230

As white dwarfs cool down, their atmospheric composition evolves due to various physical mechanisms. The so-called Hot DQ white dwarfs are characterized by their large masses (M>0.9 Msol) and ionized carbon atmospheres. Even after over a decade after their discovery, their spectral evolution remains unclear, and neither their progenitor nor descendant atmospheric compositions have been clearly identified. Progress on this issue has been mostly thwarted by a small number of known of Hot DQ as well as candidates for the surrounding spectral evolution steps. We have identified 25 white dwarfs using Gaia XP spectra that are promising Hot DQ white dwarfs or one of their progenitors/descendants. 15 of these will be observable this semester. Observing these targets with Gemini would allow us to confirm their atmospheric composition, create a statistically significant sample of these stars and put robust constraints on possible evolution scenarios for Hot DQs.