2022ApJ...938...59S

The physics of particle acceleration at supernova remnant (SNR) shocks is one of the most intriguing problems in astrophysics. SNR RCW 86 provides a suitable environment for understanding the physics of particle acceleration because one can extract the information on both accelerated particles and acceleration environment in the same regions through the bright X-ray emission. In this work, we study X-ray proper motions and spectral properties of the southwestern region of RCW 86. The proper motion velocities are found to be ∼300-2000 km s^–1 at a distance of 2.8 kpc. We find two inward-moving filaments, which are more likely reflected shocks rather than reverse shocks. Based on the X-ray spectroscopy, we evaluate thermal parameters such as the ambient density and temperature, and nonthermal parameters such as the power-law flux and index. From the decrease in flux over time of several nonthermal filaments, we estimate the magnetic field amplitudes to be ∼30-100 μG. Gathering the physical parameters, we then investigate parameter correlations. We find that the synchrotron emission from thermal-dominated filaments is correlated with the ambient density n_e as (power-law flux) $\propto {n}_{{\rm{e}}}^{1.0\pm 0.2}$ and (power-law index) $\propto {n}_{{\rm{e}}}^{0.38\pm 0.10}$, and not or only weakly correlated with the shock velocity and shock obliquity. As an interpretation, we propose a shock-cloud interaction scenario, where locally enhanced magnetic turbulence levels have a great influence on local acceleration conditions.