A Suzaku Observation of the Low-Ionization Fe-Line Emission from RCW 86

The newly operational X-ray satellite Suzaku observed the southwesternquadrant of the supernova remnant (SNR) RCW 86 in February 2006 to study thenature of the 6.4 keV emission line first detected with the Advanced Satellitefor Cosmology and Astronomy (ASCA). The new data confirm the existence of theline, localizing it for the first time; most of the line emission is adjacentand interior to the forward shock and not at the locus of the continuum hardemission. We also report the first detection of a 7.1 keV line that weinterpret as the K-beta emission from low-ionization iron. The Fe-K linefeatures are consistent with a non-equilibrium plasma of Fe-rich ejecta withn_{e}t <~ 10^9 cm^-3 s and kT_{e} ~ 5 keV. This combination of low n_{e}t andhigh kT_{e} suggests collisionless electron heating in an SNR shock. The FeK-alpha line shows evidence for intrinsic broadening, with a width of 47(34--59) eV (99% error region). The difference of the spatial distributions ofthe hard continuum above 3 keV and the Fe-K line emission support a synchrotronorigin for the hard continuum.Comment: 6 pages with 6 figures. Accepted for PASJ Suzaku Special Issue (vo. 58, sp.1