Deep Chandra Observation of the Pulsar Wind Nebula Powered by the Pulsar J1846–0258 in the Supernova Remnant

We present the results of detailed spatial and spectral analysis of the pulsar wind nebula (PWN) in supernova remnant Kes 75 (G29.7–0.3) using a deep exposure with Chandra X-ray observatory. The PWN shows a complex morphology with clear axisymmetric structure. We identified a onesided jet and two bright clumps aligned with the overall nebular elongation, and an arc-like feature perpendicular to the jet direction. We interpret the arc as an equatorial torus or wisp and the clumps could be shock interaction between the jets and the surrounding medium. Spatial modeling of the features with a torus and jet model indicates a position angle 207 ± 8 for the PWN symmetry axis. The lack of any observable counter jet implies a flow velocity larger than 0.4c. Comparing to an archival observation 6 years earlier, some small-scale features in the PWN demonstrate strong variability: the flux of the inner jet doubles, and the peak of the northern clump broadens and shifts 2 outward. As recently reported from RXTE observations, magnetar-like bursts of the central pulsar occurred coincidentally 7 days before the Chandra exposure. Accompanied with the bursts is a temporary increase in the pulsar flux: during the Chandra observation, the pulsar luminosity is 6 times larger than in quiescent state, and shows substantial spectral softening from Γ = 1.1 to 1.9 with an emerging thermal component. Subject headings: pulsars: individual (PSR J1846–0258) — supernovae: individual (Kes 75) — stars: winds, outflows — X-rays: ISM