The Variable Pulsar Wind Nebula of PSR J1809-1917

PSR J1809-1917 is a young (τ = 51 kyr) energetic ( erg s^-1) radio pulsar powering a pulsar wind nebula (PWN). We report on the results of three Chandra X-ray Observatory observations that show that the PWN consists of a small (∼20″) bright compact nebula (CN) and faint extended emission seen up to 2′ from the pulsar. The CN is elongated in the northeast-southwest direction and exhibits morphological and flux variability on a timescale of a few months. We also find evidence of small arcsecond-scale jets extending from the pulsar along the same direction, and exhibiting a hard power-law (PL) spectrum with photon index Γ_jet = 1.2 ± 0.1. The more extended emission and CN share the same symmetry axis, which is also aligned with the direction toward the TeV γ-ray source HESS J1809-193, supporting their association. The spectrum of the extended nebula (EN) fits an absorbed PL with about the same slope as that of the CN, Γ_CN ≈ Γ_EN = 1.55 ± 0.09; no spectral changes across the EN's 2 pc extent are seen. The total PWN 0.5-8 keV luminosity is L _PWN ≈ 9 10³² erg s^-1, about half of which is due to the EN.