2009ApJ...706.1269L

We present a Chandra X-ray observation of the very high energy γ-ray source HESS J1640-465. We identify a point source surrounded by a diffuse emission that fills the extended object previously detected by XMM-Newton at the centroid of the HESS source, within the shell of the radio supernova remnant (SNR) G338.3 - 0.0. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula (PWN) and extends asymmetrically to the southwest of a point source presented as a potential pulsar. The spectrum of the putative pulsar and compact nebula are well characterized by an absorbed power-law model which, for a reasonable N_H value of 14x10²²/cm2, exhibit an index of 1.1 and 2.5 respectively, typical of Vela-like PWNe. We demonstrate that, given the H I absorption features observed along the line of sight, the SNR and the H II surrounding region are probably connected and lie between 8 kpc and 13 kpc. The resulting age of the system is between 10 and 30 kyr. For a 10 kpc distance (also consistent with the X-ray absorption) the 2-10 keV X-ray luminosities of the putative pulsar and nebula are L_PSR ∼ 1.3x10³³ d ²_10 kpc_ erg/s and L_PWN∼ 3.9x10³³ d ² ₁₀ erg/s (d₁₀= d/10 kpc). Both the flux ratio of L_PWN/L_PSR ∼ 3.4 and the total luminosity of this system predict a pulsar spin-down power around E{_dot} ∼ 4x10³⁶ erg/s. We finally consider several reasons for the asymmetries observed in the PWN morphology and discuss the potential association with the HESS source in terms of a time-dependent one-zone leptonic model.