On the presence of ultrafast outflows in the WAX sample of Seyfert galaxies

The study of winds in active galactic nuclei (AGNs) is of utmost importance as they may provide the long sought-after link between the central black hole and the host galaxy, establishing the AGN feedback. Recently, Laha et al. reported the X-ray analysis of a sample of 26 Seyferts observed with XMM-Newton, which are part of the so-called warm absorbers in X-rays (WAX) sample. They claim the non-detection of Fe K absorbers indicative of ultrafast outflows in four observations previously analysed by Tombesi et al. They mainly impute the Tombesi et al. detections to an improper modelling of the underlying continuum in the E = 4-10 keV band. We therefore re-address here the robustness of these detections and we find that the main reason for the claimed non-detections is likely due to their use of single events only spectra, which reduces the total counts by 40 per cent. Performing a re-analysis of the data in the whole E = 0.3-10 keV energy band using their models and spectra including also double events, we find that the blueshifted Fe K absorption lines are indeed detected at > 99 per cent. This work demonstrates the robustness of these detections in XMM-Newton even including complex model components such as reflection, relativistic lines and warm absorbers.