Nucleonic gamma-ray production in Pulsar Wind Nebulae

Observations of the inner radian of the Galactic disk at very high energy (VHE) gamma-rays have revealed at least 16 new sources. Besides shell type supernova remnants, pulsar wind nebulae (PWN) appear to be a dominant source population in the catalogue of VHE gamma-ray sources. Except for the Crab nebula, the newly discovered PWN are resolved at VHE gamma-rays to be spatially extended (5-20 pc). Currently, at least 3 middle aged (t > 10 kyrs) PWN (Vela X, G18.0-0.7, and G313.3+0.6 in the “Kookaburra” region) and 1 young PWN MSH 15-52 (t = 1.55 kyrs) have been identified to be VHE emitting PWN (sometimes called “TeV Plerions”). Two more candidate “TeV Plerions” have been identifed and have been reported at this conference [1]. In this contribution, the gamma-ray emission from Vela X is explained by a nucleonic component in the pulsar wind. The measured broad band spectral energy distribution is compared with the expected X-ray emission from primary and secondary electrons. The observed Xray emission and TeV emission from the three middle aged PWN are compared with each other.