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 Issue A&A Volume 429, Number 2, January II 2005 489 - 495 Galactic structure, stellar clusters and populations http://dx.doi.org/10.1051/0004-6361:20041385

A&A 429, 489-495 (2005)
DOI: 10.1051/0004-6361:20041385

## Gamma-ray luminosity properties of gamma-ray pulsars

L. Zhang1, 2, Z. X. Han2 and Z. J. Jiang2

1  National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, Kunming, PRC, PR China
e-mail: astroynu@public.km.yn.cn
2  Department of Physics, Yunnan University, Kunming, PR China

(Received 2 June 2004 / Accepted 30 August 2004 )

Abstract
Based on a new self-consistent outer gap model, we statistically study luminosity properties of  -ray pulsars with ages of   yr in the Galaxy as well as those with ages of   yr in the Gould belt using a Monte Carlo method, where the  -ray beaming effect has been included. Generally, the relation between  -ray luminosity,  , and pulsar spin-down power,  , can be expressed as  , where is a parameter that depends on the galactic latitude and the  -ray threshold. For a given  -ray threshold (for example, the EGRET threshold or GLAST threshold), the parameter  is an increasing function of the galactic latitude. For the EGRET threshold,  changes smoothly with the galactic latitude. For the GLAST threshold, however,  has a minimum at  , and  increases by a factor of ~ 2 at the range of  relative to  at  , and then increases smoothly as the galactic latitude further increases. The reason for this is that high galactic latitude  -ray pulsars are dominated by mature pulsars. In fact, the ratio of  -ray pulsars with their ages of  > 106 yr to all simulated  -ray pulsars also increases with the galactic latitude. For the  -ray pulsars produced in a fixed range of galactic latitude, the parameter  increases slightly with the sensitivity of  -ray detector.

Key words: gamma-rays: theory -- stars: pulsars: general -- stars: neutron -- stars: statistics