White dwarfs within 25pc of the Sun

We compare this ratio with the results of other studies. We find that at least 11% of the WDs within 25pc of the Sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies, or debris disks orbiting them.

Our volume-limited sample reveals a pileup of DC WDs at the well-known cutoff in DQ WDs at T_eff_~6000K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic WDs in the 25pc sample is at least 8% in our volume-limited sample, dominated by cool WDs.

We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ WDs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores.