  Stars with masses in the range 7-10Msun end their lives either as massive
white dwarfs or weak type II supernovae, and there are only limited
observational constraints of either channel. Here we report the detection of
two white dwarfs with large photospheric oxygen abundances, implying that they
are bare oxygen-neon cores and that they may have descended from the most
massive progenitors that avoid core-collapse.
