New non-Gaussian feature in COBE-DMR 4 year maps

We extend a previous bispectrum analysis of the cosmic microwave background temperature anisotropy, allowing for the presence of correlations between different angular scales. We find a strong non-Gaussian signal in the "inte rscale" components of the bispectrum: their observed values concentrate clo se to zero instead of displaying the scatter expected from Gaussian maps. T his signal is present over the range of multipoles l = 6-18, in contrast wi th previous detections. We attempt to attribute this effect to galactic for eground contamination, pixelization effects, possible anomalies in the nois e, documented systematic errors studied by the COBE team, and the effect of assumptions used in our Monte Carlo simulations. Within this class of syst ematic errors, the confidence level for rejecting Gaussianity varies betwee n 97% and 99.8%.