Suzaku observation of an iron K-shell line in the spiral galaxy NGC 6946

Abstract

An emission line at ~6.7 keV is attributable to a He-like iron K-shell transition, which indicates existence of a thin thermal plasma with a temperature of several keV. Using Suzaku archival data, we searched for the iron K-line from the spiral galaxy NGC 6946, and found the iron K-line at 6.68+/-0.07 keV at the 3.1 sigma level in the central r<2.'5 region. The iron line luminosity from the central region was estimated to be (2.3+/-1.2)x10^{37} erg s^{-1} at a distance of 5.5 Mpc. The origin of the iron emission line is discussed.