Sub-luminous gamma-Ray pulsars

TL;DR

This paper investigates sub-luminous gamma-ray pulsars that are fainter than expected, exploring whether their faintness is due to orientation effects and proposing a lower-altitude emission model.

Contribution

It introduces the concept of sub-luminous gamma-ray pulsars and discusses their potential as an orientation effect with a proposed lower-altitude emission mechanism.

Findings

Sub-luminous pulsars are fainter than the typical gamma-ray luminosity trend.

Limited geometrical data suggest these pulsars may have aligned geometries.

A lower-altitude, lower-power accelerator gap could explain their gamma-ray emission.

Abstract

Most pulsars observed by the Fermi LAT have gamma-ray luminosities scaling with spindown power Edot as L_gamma (Edot x 10^33 erg/s)^{1/2}. However, there exist one detection and several upper limits an order of magnitude or more fainter than this trend. We describe these `sub-luminous' gamma-ray pulsars, and discuss the case for this being an orientation effect. Of the 12 known young radio pulsars with Edot>10^34 erg/s and d<2kpc several are substantially sub-luminous. The limited available geometrical constraints favor aligned geometries for these pulsars, although no one case for alignment is compelling. In this scenario GeV emission detected from such sub-luminous pulsars can be due to a lower altitude, lower-power accelerator gap.