A multicomponent model for the optical to gamma-ray emission from the Crabpulsar

We present a multicomponent model to explain the features of the pulsed emission and spectrum of the Crab Pulsar, on the basis of X and gamma-ray observations performed with BeppoSAX, INTEGRAL and CGRO. This model explains the evolution of the pulse shape and of the phase-resolved spectra, ranging from the optical/UV to the GeV energy band, on the assumption that the observed emission is due to several components. The first component, C_O, is assumed to have the pulsed double-peaked profile observed at the optical frequencies, while the second component, C_X, isdominant in the interpeak and second peak phase regions. The spectra of these components are modelled with log-parabolic laws. Moreover, to explain the properties of the pulsed emission in the MeV-GeV band, we introduce two more components, C_O_gamma and C_X_gamma, with phase distributions similar to those of C_O and C_X and log-parabolic spectra with the same curvature but different peak energies. This multicomponent model is able to reproduce both the broadband phase-resolved spectral behaviour and the changes of the pulse shape with energy. We also propose some possible physical interpretations in which C_O and C_X are emitted by secondary pairs via a synchrotron mechanism while C_O_gamma and C_X_gamma can originate either from Compton scattered or primary curvature photons.