SS 433 Eastern Jet Turbulence Revealed by Spatially-Resolved IXPE Data Analysis

Abstract

The extended X-ray jet (EXJ) of SS 433/W50 shows hard X-ray and very-high-energy gamma-ray emission, indicating strong particle acceleration, likely sensitive to the EXJ magnetic field structure and turbulence. To study this field, we re-analyze the 2023 Imaging X-ray Polarimetry Explorer (IXPE) observation of the eastern EXJ using the publicly available polarization fitting package LeakageLib. Compared with standard PCUBE and spectropolarimetric analyses, this approach improves the polarization constraints and enables spatially resolved polarization measurements. Dividing the EXJ into head, spine, and sheath regions with independent polarization properties, we find significant (>3 sigma) improvement over a single-zone model. The sheath exhibits lower polarization than the head and spine, while the electric vector position angles are consistent across all regions, indicating magnetic fields aligned with the jet axis. The measurements imply enhanced magnetic turbulence at the jet boundary, potentially driven by Kelvin-Helmholtz instabilities.