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Issue A&A
Volume 459, Number 3, December I 2006
Page(s) 859 - 870
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20065118



A&A 459, 859-870 (2006)
DOI: 10.1051/0004-6361:20065118

The optical to $\gamma$-ray emission of the Crab pulsar: a multicomponent model

E. Massaro1, R. Campana1, G. Cusumano2, and T. Mineo2

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 $\gamma$-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, CO, is assumed to have the pulsed double-peaked profile observed at the optical frequencies, while the second component, CX, 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, $C_{O\gamma}$ and $C_{X\gamma}$, with phase distributions similar to those of CO and CX 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 CO and CX 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.


Key words: stars: pulsars: individual: crab pulsar (PSR B0531+21) -- X-rays: stars -- gamma rays: observations -- stars: pulsars: general



© ESO 2006


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