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.