2011ApJ...742...62V

The pulsar wind nebula associated with PSR J1826-1334, HESS J1825-137, is a bright very high energy (VHE) source with an angular extent of ∼1° and spatially resolved spectroscopic TeV measurements. The gamma-ray spectral index is observed to soften with increasing distance from the pulsar, likely the result of cooling losses as electrons traverse the nebula. We describe analysis of X-ray data of the extended nebula, as well as three-dimensional time-dependent spectral energy distribution modeling, with emphasis on the spatial variations within HESS J1825-137. The multi-wavelength data place significant constraints on electron injection, transport, and cooling within the nebula. The large size and high nebular energy budget imply a relatively rapid initial pulsar spin period of 13±7 ms and an age of 40±9 kyr. The relative fluxes of each VHE zone can be explained by advective particle transport with a radially decreasing velocity profile with v(r)∝r ^–0.5. The evolution of the cooling break requires an evolving magnetic field which also decreases radially from the pulsar, B(r,t) r^–0.7 {dot}E(t)^1/2. Detection of 10 TeV flux ∼80 pc from the pulsar requires rapid diffusion of high-energy particles with τ_esc ≈ 90(R/10pc)²(E_e/100TeV)^–1 year, contrary to the common assumption of toroidal magnetic fields with strong magnetic confinement. The model predicts a rather uniform Fermi Large Area Telescope (LAT) surface brightness out to ∼1° from the pulsar, in good agreement with the recently discovered LAT source centered 0°.5 southwest of PSR J1826-1334 with extension 0°.6±0°.1.