Temperature Equilibration Behind the Shock Front: an Optical and X-ray
  Study of RCW 86
  We study the electron-proton temperature equilibration behind several shocks
of the RCW 86 supernova remnant. To measure the proton temperature, we use
published and new optical spectra, all from different locations on the remnant.
For each location, we determine the electron temperature from X-ray spectra,
and correct for temperature equilibration between the shock front and the
location of the X-ray spectrum. We confirm the result of previous studies that
the electron and proton temperatures behind shock fronts are consistent with
equilibration for slow shocks and deviate for faster shocks. However, we can
not confirm the previously reported trend of the electron temperature to proton
temperature ratio of 1/v^2.
