Gamma-Ray Pulsars in the Unidentified Population: The ‘Outer Gap’ Perspective

Abstract

Given that pulsars and AGN are the only identified GeV point sources, it isn’t too bold to infer a substantial pulsar contribution to the Unidentified population. Specific models however predict differently the types of pulsars present in the observed sample. The dominant factors are the efficiency of spindown-gamma conversion, the high energy beam shape and the gamma ray spectrum. I’ll review briefly the main features of the `outer gap’ picture. Consequences for the relative numbers and Galactic distributions of the objects expected in the EGRET survey are then discussed, including young pulsars, `Geminga’s, binaries and millisecond pulsars. With recent counterpart work, we can already test and refine these predictions. The final, and main, point is that what we actually see teaches us in return important lessons about the pulsar physics. With up to a third of the spindown luminosity appearing as GeV gamma rays, these lessons give powerful constraints on the nature of the pulsar machine