X-ray and Gamma-ray Emission from Pulsar Magnetospheres

For polar-cap models based on electromagnetic cascades induced by curvature radiation of beam particles we calculate broad-band high-energy spectra of pulsed emission expected for classical (∼ 10 G) and millisecond pulsars (∼ 10 G). The spectra are a superposition of curvature and synchrotron radiation components and most of their detailed features depend significantly on the magnetic field strength. The relations of expected pulsed luminosity LX (between 0.1 keV and 10 keV) as well as Lγ (above 100 keV) to the spin-down luminosity Lsd are presented. We conclude that spectral properties and fluxes of pulsed non-thermal X-ray emission of some objects, like the Crab or the millisecond pulsar B1821−24, pose a challenge to the polar-cap models based on curvature and synchrotron radiation alone. On the other hand, such models may offer an explanation for the case of B1706−44.