2007MNRAS.378..955K

We report on the detection of negative superhumps in KR Aur, a typical VY Scl star. The observations were obtained with a multi-channel photometer over 107 h. The analysis of the data clearly revealed brightness variations with a period of 3.771 (±0.005) h. This is 3.5 per cent shorter than P_orb, suggesting that the observed oscillation is a negative superhump. Negative superhumps in VY Scl stars are widespread. The discovery of powerful soft X-rays from V751 Cyg suggests that VY Scl stars may contain white dwarfs, on to which nuclear burning of the accreted material occurs. If this suspicion is correct, it is possible that the powerful radiation emerging from the white dwarf may cause a tilt of the accretion disc to the orbital plane, and its retrograde precession may produce the negative superhumps seen in VY Scl stars.