High-resolution X-ray observations of the pulsar wind nebula associated with the gamma-ray sources HESS J1640-465

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 14 × 1022 cm–2, 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 ~ 1.3 × 1033 d 2 10 kpc erg s–1 and L PWN ~ 3.9 × 1033 d 2 10 erg s–1 (d 10 = 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 $\dot{E} \sim 4 \times 10^{36}\;{\rm erg\;s}^{-1}$. 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