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