Spectral parameters of J1605 as a function of time as measured in the RGS observations (data points; see text and Table 8 for details). The model fit to the observations in XSPEC is tbabs(bbody-gauss). Circles (black) and squares (red) show the subgroups of old and new observations of the source, obtained respectively in 2002/2003 and after 2012. The analysis of EPIC data (see Fig. 2) are for the observations in the new subgroup (MJD >  56 000). Shaded areas are the results of the fits of RGS1/2 stacked spectra in the two subgroups, with 1σ standard deviations.