Continuum normalized, co-added fluxed spectrum of RGS1 and RGS2 data at the wavelength around the putative redshift 0.09017 Ne IX Heα absorption line. The FUV predicted line centroid wavelength is shown with the orange line, while the dotted red curve shows the expected absorption signal based on the simultanous fitting of XMM-Newton and Chandra data with the redshifted slab model (Sect. 5.1.1).