The WISE Light Curves of Polars

We have extracted the WISE (Wide-field Infrared Survey Explorer) single-exposure data for a sample of 72 polars, which are highly magnetic cataclysmic variables (CVs). We combine these data with both published and unpublished optical and infrared data to explore the origins of the large amplitude variations seen in these systems. In nearly every case, we find evidence for cyclotron emission in the WISE bandpasses. We find that the derived magnetic field strengths for some polars are either too high, or cyclotron emission from lower field components, located spatially coincident to the main accreting poles, must be occurring. We have also estimated field strengths for a number of polars where no such values exist. In addition, contrary to expectations, we find that emission from the fundamental cyclotron harmonic (n = 1) appears to be nearly always present when the magnetic field is of the appropriate strength that it falls within a WISE bandpass. We find that the light curves for RBS 490, an ultrashort-period (46 minutes) CV, suggest that it is a polar. Modeling its spectrum indicates that its donor star is much hotter than expected. Nearly all of the detected polars show 11.5 μm (“W3 band”) excesses. The general lack of variability seen in the W3 bandpass light curves for higher-field polars demonstrates that these excesses are probably not due to cyclotron emission. There is circumstantial evidence that these excesses can be attributed to bremsstrahlung emission from their accretion streams. Reduction of the Spitzer 24 μm image of V1500 Cyg shows that it appears to be located at the center of a small nebula.