Spectra (black data points, left-hand axes, 2.5 keV binning) for V5668, integrated between days –7 and +37 after the optical maximum. Also shown are the SPI background spectra (red, right-hand axes) in the energy range 450–500 keV (panel a) and 1240–1310 keV (panel b). The background is well suppressed, and no significant line-like or continuum excesses above background can be identified. The zero-flux level is indicated by green solid lines. See text for details.