Deep Chandra Observation of the Pulsar Wind Nebula Powered by the Pulsar J1846-0258 in the Supernova Remnant Kes 75

TL;DR

This study provides a detailed spatial and spectral analysis of the pulsar wind nebula in Kes 75 using deep Chandra observations, revealing complex morphology, variability, and spectral changes linked to pulsar activity.

Contribution

It offers the first detailed spatial and spectral modeling of the PWN in Kes 75, identifying jet, torus, and shock features, and documents temporal variability and spectral evolution of the nebula and pulsar.

Findings

Identification of a one-sided jet and bright clumps in the PWN.

Detection of significant variability in the nebula and pulsar over 6 years.

Observation of spectral softening and thermal component emergence in the pulsar.

Abstract

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 one-sided jet and two bright clumps aligned with the overall nebular elongation, and an arc-like feature perpendicular to the jet direction. Further spatial modeling with a torus and jet model indicates a position angle $207\arcdeg\pm8 \arcdeg$ for the PWN symmetry axis. We interpret the arc as an equatorial torus or wisp and the clumps could be shock interaction between the jets and the surrounding medium. 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. In addition, the pulsar flux increases by 6 times, showing substantial spectral softening from $\Gamma$=1.1 to 1.9 and an emerging thermal component which was not observed in the first epoch. The changes in the pulsar spectrum are likely related to the magnetar-like bursts of the pulsar that occurred 7 days before the Chandra observation, as recently reported from RXTE observations.