The optical to γ-ray emission of the Crab pulsar: a multicomponent model

¹ Dipartimento di Fisica, Università di Roma “La Sapienza”, Piazzale A. Moro 2, 00185, Roma, Italy e-mail: enrico.massaro@uniroma1.it
² INAF-IASF, Sezione di Palermo, via Ugo La Malfa 153, 90146, Palermo, Italy

Received: 1 March 2006
Accepted: 20 June 2006

Abstract

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 γ-ray observations obtained 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 more 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, is dominant in the interpeak and second peak phase regions. The spectra of these components are modelled with log-parabolic laws and their spectral energy distributions have peak energies at 12.2 and 178 keV, respectively. To explain the properties of the pulsed emission in the MeV-GeV band, we introduce two more components, and , with phase distributions similar to those of C_O and C_X and log-parabolic spectra with the same curvature but peak energies at about 300 MeV and 2 GeV. 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 and can originate either from Compton scattered or primary curvature photons.