PULSAR DEATH LINES AND DEATH-VALLEY

In most models of a spinning-down neutron star's magnetosphere, the star turns off as a radio pulsar when it can no longer produce electron-positron pairs. The period (P) at turnoff depends upon the magnitude and the structure of the star's surface magnetic field. Only the magnetic dipole component of this field (B(p)) is inferred from the observed spin-down rate of a pulsar. Turnoff should occur in a B(p) - P death valley with well-defined boundaries rather than a death line. It is argued that most of the additional higher energy pulsed flux from rapidly spinning pulsars like the Crab and Vela pulsars is a consequence of pair-production in the outer magnetosphere. The necessary parameters for sustaining pair production there leads to a separated death tine, or possibly a death valley, which does not fall in the death valley of radio pulsars. Maximum high-energy gamma-ray luminosity and probably a quenching of radio emission are expected just above this death line is reached. This is compared to observations of canonical and millisecond radio pulsars and gamma-ray sources.