K-band spectrum of J0529 from ERIS. The upper panel shows the data (blue; the narrow features at the long end of the band are due to imperfect atmospheric correction) and the fit (orange), with the H I lines marked (the location of the [O III] lines are also marked; the 4363 Å line is expected to be 10–100 times weaker than those at 4959 Å and 5007 Å, the peaks of which are out of the spectral range). Also shown are the atmospheric transmission and the residual, indicating which regions have been excluded from the fit. The lower panel shows the components of the fit: the H I lines (black), Fe II complex (red), and a component that represents either poor slope correction at the band edge (as seen also at the short end of the band) or a possible blue wing on the [O III] line.