X-ray studies of the gamma-ray pulsar J1826-1256 and its pulsar wind nebula with Chandra and XMM-Newton

We have analysed archival XMM-Newton and Chandra observations of the γ-ray radio-quiet pulsar J1826-1256 and its pulsar wind nebula. The pulsar spectrum can be described by a power-law model with photon index Γ ≈ 1. We find that the nebular spectrum softens with increasing distance from the pulsar, implying synchrotron cooling. The empirical interstellar absorption-distance relation gives a distance of ≈3.5 kpc to J1826-1256. We also discuss the nebula geometry and the association between the pulsar, the very high energy source HESS J1826-130, the supernova remnant candidate G18.45-0.42 and the open star cluster Bica 3.