2013MNRAS.433.1599L

A surprisingly large fraction (70percent) of hot, carbon-dominated atmosphere (DQ) white dwarfs are magnetic and/or photometrically variable on short time-scales up to ∼ 1000s. However, here, we show that the hot DQ magnetic white dwarf SDSS J000555.90-100213.5 is photometrically variable by 11percent on a longer time-scale, with a period of 2.110±0.045d. We find no evidence of the target fluctuating on short time-scales at an amplitude of ≲ ±0.5percent. 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 rotation of the magnetic hot DQ white dwarf. We suggest that some hot DQ white dwarfs, varying on short time-scales, 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.