Suzaku observations of Fe K-shell lines in the supernova remnant W51C and hard X-ray sources in the proximity

We have investigated the Fe K-shell lines in W51C with Suzaku, which has the largest effective area in the Fe K-shell band in contemporary X-ray astronomy satellites. The observed 6.7 keV line intensity in the W51C region is consistent with that of the background emission. On the other hand, the observed 6.4 keV line intensity is higher than that of the background with a significance level of 2.0 sigma. The most likely origin of the enhancement is the interaction between low-energy CRs and molecular clouds. The local enhancement of the 6.7 keV line in the compact H II region G49.0-0.3 was found for the first time with a significance level of 3.4𝜎. Spectral analysis revealed that the temperature of the thermal plasma accompanied by the Fe line is kT = 3.0+0.8-0.7 keV, which could be explained by a thermal plasma produced by the stellar winds of O stars.