Infrared-to-ultraviolet wavelength-dependent variations within the pulse profile peaks of the Crab Nebula pulsar

We present evidence of wavelength-dependent variations within the infrared, optical, and ultraviolet pulse profile peaks of the Crab Nebula pulsar. The leading and trailing edge half-width half-maxima of the peaks display clear differences in their wavelength dependences. In addition, phase-resolved infrared-to-ultraviolet color spectra show significant variations from the leading to trailing edges of the peaks. The color variations between the leading and trailing edges remain significant over phase differences smaller than 0.0054, corresponding to timescales of <180 mu s. These results are not predicted by any current models of the pulsar emission mechanism and offer new challenges for the development of such models.