2010MNRAS.407.1819R

We present multiwavelength observations of the helium-dominated accreting binary KL Dra which has an orbital period of 25 min. Our ground-based optical monitoring programme using the Liverpool Telescope has revealed KL Dra to show frequent outbursts. Although our coverage is not uniform, our observations are consistent with the outbursts recurring on a time-scale of ∼60 d. Observations made using Swift show that the outbursts occur with a similar amplitude and duration (2 weeks) at both UV and optical energies. Although KL Dra is a weak X-ray source, we find no significant evidence that the X-ray flux varies over the course of an outburst cycle. We can reproduce the main features of the 60-d outburst cycle using the disc instability model and a helium-dominated accretion flow. Although the outbursts of KL Dra are very similar to those of the hydrogen-accreting dwarf novae, we cannot exclude the fact that they are the AM CVn equivalent of WZ Sge-type outbursts. With outbursts occurring every ∼2 months, KL Dra is an excellent target to study helium-dominated accretion flows in general.