Top: part of the X-shooter counts spectrum of BZB J0816–1311 in the UVB arm before flux calibration and telluric corrections. The absorption features are identified as corresponding to the Mg II doublet in three intervening systems, respectively at z = 0.1902, z = 0.2336, and z = 0.2882. The corresponding positions are indicated by the dashed vertical lines. Bottom: UV-to-NIR spectrum of BZB J0816–1311 obtained with X-shooter after flux calibration and telluric corrections. The spectrum is dominated by the non-thermal emission from the nucleus and is well described by a power law (see Table 9 for details). No other extragalactic spectral features are identified.