ELECTRON-POSITRON HEATING AND THE ECLIPSING MILLISECOND PULSAR PSR-1957+20

The companion in the eclipsing millisecond pulsar system PSR 1957 + 20 appears to be strongly heated by the pulsar and may also be rapidly losing mass due to that heating. We present a new mechanism by which the heating may be accomplished: diffusion of mildly relativistic electron-positron pairs from the pulsar's relativistic wind through a thermal wind issuing from the companion. Wave-particle scattering regulates the depth at which the pairs deposit their energy; requirements of self-consistency place bounds on the wave spectrum and pair distribution function. If the pairs carry ≳10% of the pulsar spin-down luminosity, and the companion's heavy element abundance is subsolar, the heating rate can be adequate to drive a wind with sufficient momentum flux to explain the eclipse geometry. Annihilation photons then heat the companion beneath its photosphere and supply a significant part of the power for the optical luminosity. This model also suggests B that the eclipse duration decreases sharply above a critical photon frequency.