Cubic anomalies in the Wilkinson Microwave Anisotropy Probe

We perform a frequentist analysis of the bispectrum of the Wilkinson Microwave Anisotropy Probe first-year data. We find clear signal domination up to 200, with overall consistency with Gaussianity, except for the following features. There is a flat patch (i.e. a low 2 region) in the same-l components of the bispectrum spanning the range l=32-62; this may be interpreted as ruling out Gaussianity at the 99.6 per cent confidence level. There is also an asymmetry between the north and south inter-l bispectrum components at the 99 per cent confidence level. The preferred asymmetry axis correlates well with the (l,b) = (57, 10) direction quoted in the literature for asymmetries in the power spectrum and three-point correlation function. However, our analysis of the quadrupole (its bispectrum and principal axes) fails to make contact with previously claimed anomalies.