A surprisingly large fraction ( 70 % ) of hot , carbon dominated atmosphere ( DQ ) white dwarfs are magnetic and/or photometrically variable on short timescales up to \sim 1000 s. However , here we show that the hot DQ magnetic white dwarf SDSS J000555.90-100213.5 is photometrically variable by 11 % on a longer timescale , with a period of 2.110 \pm 0.045 days .
We find no evidence of the target fluctuating on short timescales at an amplitude of \lesssim \pm 0.5 \% .
Short period hot DQ white dwarfs have been interpreted as non-radial pulsators , but in the case of SDSS J0005-1002 , it is more likely that the variability is due to the magnetic hot DQ white dwarf rotating .
We suggest that some hot DQ white dwarfs , varying on short timescales , should be more carefully examined to ascertain whether the variability is due to rotation rather than pulsation .
All hot DQs should be monitored for long period modulations as an indicator of rotation and magnetism .