Highly ionized iron absorption lines from outflowing gas in the X-ray spectrum of NGC 1365

We present the discovery of four absorption lines in the X-ray spectrum of the Seyfert galaxy NGC 1365, at energies between 6.7 and 8.3 keV. The lines are detected with high statistical confidence (from 120 j for the strongest to ∼4 j for the weakest) in two XMM-Newton observations 60 ks long. We also detect the same lines, with a lower signal-to-noise ratio (but still 12 j for each line), in two previous shorter (∼10 ks) XMM-Newton observations. The spectral analysis identifies these features as Fe xxv and Fe xxvi Ka and Kb lines, outflowing with velocities varying between ∼1000 and ∼5000 km s1 among the observations. These are the highest quality detections of such lines so far. The high equivalent widths [EW(Ka) ∼ 100 eV] and the Ka/Kb ratios imply that the lines are due to absorption of the AGN continuum by a highly ionized gas with column density NH ∼ 5 # 1023 cm2 at a distance of ∼(50–100)RS from the continuum source.