Simultaneous IR and optical light curves of 2A0311-227

The complex wavelength dependence^1-4 shown by the light curves of the AM Herculis type binaries such as 2A0311-227 (EF_ΔERI) and AM Her itself has led to suggestions^5-7 that accretion occurs onto both magnetic poles of the white dwarf. The field strengths of the two poles being sufficiently different that one pole dominates at optical wavelengths, while the other produces most of the emission in the IR. Other authors³ have argued for a single pole model explaining the wavelength dependence of the light curves in terms of the rapidly changing cyclotron opacity with wavelength. An observational method of distinguishing between these two models is provided by the rapid flickering, which is a characteristic property of the light curves at both optical and IR wavelengths. We report here that the optical and IR flickering of 2A0311-227 are highly correlated indicating that in this object the dominant source of cyclotron radiation at both wavelengths is the same accretion column.