A Crab pulsar model - X-ray, optical, and radio emission

Abstract

The predicted electron-positron pair production in the Crab pulsar outer magnetosphere at the ''outer gap,'' 3 x 10/sup 7/ cm from the neutron star, is considered as a source of pulses at all observed energies. A pulse and interpulse that are roughly symmetric with separation somewhat less than 180/sup 0/ are expected for arbitrary angles between the stellar magnetic moment and spin. The model gives optical and X-ray pulses from inverse Compton scattering of radio photons by e/sup +/ and e/sup -/ that are created with ..gamma../sub parallel3/ and ..gamma../sub perpendicular4/ relative to B. The Compton boosting occurs during the time before synchrotron radiation reduces ..gamma../sub perpendicular/to below approx.2. The lower-energy pulsed X-ray polarization is predicted to be similar to the optical pulse polarization. The synchrotron radiation gives very hard X-rays and ..gamma..-rays up to 10/sup 3/ MeV. The Crab radio emissions, except for the precursor, are also predicted to originate from the ''outer gap.'' Because of the much weaker magnetic fields near the light cylinder in much slower pulsars, significant Compton boosting and radio emission within the outer gap are possible only in the fastest pulsar with parameters similar to those of the Crab.