Discovery of Pulsed Gamma Rays from the Young Radio Pulsar PSR J1028-5819 with the Fermi Large Area Telescope

TL;DR

This paper reports the discovery of gamma-ray pulsations from the young radio pulsar PSR J1028-5819 using the Fermi LAT, confirming it as the gamma-ray source previously associated with EGRET, and analyzing its emission characteristics.

Contribution

First detection of gamma-ray pulsations from PSR J1028-5819 with Fermi LAT, establishing it as a gamma-ray pulsar and clarifying its association with earlier gamma-ray sources.

Findings

Gamma-ray pulsations detected with phase separation of 0.460.

Gamma-ray efficiency estimated at 10-20%.

Disentanglement of previous gamma-ray sources into at least two sources.

Abstract

Radio pulsar PSR J1028-5819 was recently discovered in a high-frequency search (at 3.1 GHz)in the error circle of the EGRET source 3EG J1027-5817. The spin-down power of this young pulsar is great enough to make it very likely the counterpart for the EGRET source. We report here the discovery of gamma-ray pulsations from PSR J1028-5819 in early observations by the Large Area Telescope (LAT) on the Fermi Gamma-Ray Space Telescope. The gamma-ray light curve shows two sharp peaks having phase separation of 0.460 +- 0.004, trailing the very narrow radio pulse by 0.200 +- 0.003 in phase, very similar to that of other known $\gamma$-ray pulsars. The measured gamma-ray flux gives an efficiency for the pulsar of 10-20% (for outer magnetosphere beam models). No evidence of a surrounding pulsar wind nebula is seen in the current Fermi data but limits on associated emission are weak because the source lies in a crowded region with high background emission. However, the improved angular resolution afforded by the LAT enables the disentanglement of the previous COS-B and EGRET source detections into at least two distinct sources, one of which is now identified as PSR J1028-5819.