XMM-Newton RGS spectra in photon flux units per 10³ s (=ks). The 2021d37.1 spectrum (grey shading) is compared to the same-epoch 2006d39.7 spectrum (down-scaled by factor 5; red) and the bright-only 2006 spectrum on day 26.1 (black). The top panel shows a larger wavelength range while the bottom panel zooms into the variable soft excess with several unknown narrow emission and absorption features, where only the corresponding wavelength is indicated.