The X-ray synchrotron emission of RCW 86 and the implications for its   age
  We report here X-ray imaging spectroscopy observations of the northeastern shell of the supernova remnant RCW 86 with Chandra and XMM-Newton. Along this part of the shell the dominant X-ray radiation mechanism changes from thermal to synchrotron emission. We argue that both the presence of X-ray synchrotron radiation and the width of the synchrotron emitting region suggest a locally higher shock velocity of V_s = 2700 km/s and a magnetic field of B = 24+/-5 microGauss. Moreover, we also show that a simple power law cosmic ray electron spectrum with an exponential cut-off cannot explain the broad band synchrotron emission. Instead a concave electron spectrum is needed, as predicted by non-linear shock acceleration models. Finally, we show that the derived shock velocity strengthens the case that RCW 86 is the remnant of SN 185. 
Jacco Vink (1,2), Johan Bleeker (1,2) Kurt van der Heyden (3), Andrei   Bykov (4), Aya Bamba (5), Ryo Yamazaki (6) ((1) Utre...