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 infr ared, optical, and ultraviolet pulse profile peaks of the Crab Nebula pulsar. The leading and trailing edge half-width half-maxima of the pe aks display clear differences in their wavelength dependences. In addi tion, phase-resolved infrared-to-ultraviolet color spectra show signif icant variations from the leading to trailing edges of the peaks. The color variations between the leading and trailing edges remain signifi cant over phase differences smaller than 0.0054, corresponding to time scales of <180 mu s. These results are not predicted by any current mo dels of the pulsar emission mechanism and offer new challenges for the development of such models.