Low Energy X-ray Emission from Young Isolated Neutron Stars

A young neutron star with large spin-down power is expected to be closely surrounded by an e pair plasma maintained by the conversion of γ-rays associated with the star’s polar-cap and/or outer-gap accelerators. Cyclotron-resonance scattering by the e and e within several radii of such neutron stars prevents direct observations of thermal X-rays from the stellar surface. Estimates are presented for the parameters of the Planck-like X-radiation which ultimately diffuses out through this region. Comparisons with observations, especially of apparent blackbody emission areas as a function of neutron star age, support the proposition that we are learning about a neutron star’s magnetosphere rather than about its surface from observations of young neutron star thermal X-rays.