Query : 2012A&A...545A..42P

2012A&A...545A..42P - Astronomy and Astrophysics, volume 545A, 42-42 (2012/9-1)

Constraining γ-ray pulsar gap models with a simulated pulsar population.


Abstract (from CDS):

With the large sample of young γ-ray pulsars discovered by the Fermi Large Area Telescope (LAT), population synthesis has become a powerful tool for comparing their collective properties with model predictions. We synthesised a pulsar population based on a radio emission model and four γ-ray gap models (Polar Cap, Slot Gap, Outer Gap, and One Pole Caustic). Applying γ-ray and radio visibility criteria, we normalise the simulation to the number of detected radio pulsars by a select group of ten radio surveys. The luminosity and the wide beams from the outer gaps can easily account for the number of Fermi detections in 2 years of observations. The wide slot-gap beam requires an increase by a factor of ∼10 of the predicted luminosity to produce a reasonable number of γ-ray pulsars. Such large increases in the luminosity may be accommodated by implementing offset polar caps. The narrow polar-cap beams contribute at most only a handful of LAT pulsars. Using standard distributions in birth location and pulsar spin-down power ({dot}(E)), we skew the initial magnetic field and period distributions in a an attempt to account for the high {dot}(E) Fermi pulsars. While we compromise the agreement between simulated and detected distributions of radio pulsars, the simulations fail to reproduce the LAT findings: all models under-predict the number of LAT pulsars with high {dot}(E), and they cannot explain the high probability of detecting both the radio and γ-ray beams at high {dot}(E). The beaming factor remains close to 1.0 over 4 decades in {dot}(E) evolution for the slot gap whereas it significantly decreases with increasing age for the outer gaps. The evolution of the enhanced slot-gap luminosity with {dot}(E) is compatible with the large dispersion of γ-ray luminosity seen in the LAT data. The stronger evolution predicted for the outer gap, which is linked to the polar cap heating by the return current, is apparently not supported by the LAT data. The LAT sample of γ-ray pulsars therefore provides a fresh perspective on the early evolution of the luminosity and beam width of the γ-ray emission from young pulsars, calling for thin and more luminous gaps.

Abstract Copyright:

Journal keyword(s): stars: neutron - pulsars: general - gamma rays: stars - radiation mechanisms: non-thermal - methods: numerical - surveys

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 SNR G119.5+10.2 SNR 00 06.6 +72 47           ~ 249 1
2 M 1 SNR 05 34 30.9 +22 00 53           ~ 6120 1
3 NAME Geminga Psr 06 33 54.153 +17 46 12.91           ~ 1200 0
4 NAME Vela Pulsar Psr 08 35 20.65525 -45 10 35.1545     15.10     ~ 2282 1
5 PSR J1028-5819 Psr 10 28 27.888 -58 19 06.14           ~ 103 1
6 PSR B1046-58 Psr 10 48 13.0500 -58 32 06.200           ~ 265 0
7 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14046 0
8 PSR J2021+3651 Psr 20 21 05.40 +36 51 04.5           ~ 185 1
9 PSR J2229+6114 Psr 22 29 05.262 +61 14 08.48           ~ 217 2

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