Color Measurements of Dust Clouds Transiting the White Dwarf J0328-1219

The transiting dust clouds that orbit the white dwarf (WD) J0328-1219 produce dips with nearly identical depths at g ′ and R bands. This resembles a similar finding for WD 1145+017 at near-IR wavelengths, which has been interpreted as requiring an absence of small particles in the dust clouds. Whereas the lack of depth difference at optical wavelengths for J0328-1219 can be used to rule-out the presence of small particles if the dust clouds are optically thin, a constraint on the particle size distribution is not possible if the dust clouds are optically thick.