Gamma-ray luminosity properties of gamma-ray pulsars

Abstract

Based on a new self-consistent outer gap model, we statistically study luminosity properties of gamma-ray pulsars with ages of less than or equal to2 x 10(7) yr in the Galaxy as well as those with ages of less than or equal to5 x 10(6) yr in the Gould belt using a Monte Carlo method, where the gamma-ray beaming effect has been included. Generally, the relation between gamma-ray luminosity, Lgamma, and pulsar spin-down power, L-sd, can be expressed as L-gamma proportional to L-sd(delta), where delta is a parameter that depends on the galactic latitude and the gamma-ray threshold. For a given gamma-ray threshold (for example, the EGRET threshold or GLAST threshold), the parameter delta is an increasing function of the galactic latitude. For the EGRET threshold, delta changes smoothly with the galactic latitude. For the GLAST threshold, however, delta has a minimum at \b less than or equal to 5degrees, and delta increases by a factor of similar to2 at the range of \b = 5degrees-10degrees relative to delta at \b less than or equal to 5degrees, and then increases smoothly as the galactic latitude further increases. The reason for this is that high galactic latitude gamma-ray pulsars are dominated by mature pulsars. In fact, the ratio of gamma-ray pulsars with their ages of >10(6) yr to all simulated gamma-ray pulsars also increases with the galactic latitude. For the gamma-ray pulsars produced in a fixed range of galactic latitude, the parameter delta increases slightly with the sensitivity of gamma-ray detector.