Spectral energy distribution of BPS BS 16981−0016. Top panel: filter-averaged fluxes converted from observed magnitudes from different photometric surveys are shown (violet: GALEX, Bianchi et al. 2017; bright yellow: DELVE, Drlica-Wagner et al. 2021; cyan: Gaia EDR3, Riello et al. 2021; black: Gaia DR3 XP box filters, Gaia Collaboration 2023; blue: APASS9, Henden et al. 2016; yellow: SDSS, Alam et al. 2015; dark yellow: Skymapper, Onken et al. 2019; pink: UKIDSS, Lawrence et al. 2007; dark red: VIKING, Edge et al. 2013; red: 2MASS, Skrutskie et al. 2006; magenta: WISE, Schlafly et al. 2019). The respective full width at tenth maximum are shown as dashed horizontal lines. The best-fitting model, degraded to a spectral resolution of 6 Å, is plotted in grey. In order to reduce the steep SED slope the flux is multiplied by the wavelength cubed. Bottom panel: difference between synthetic and observed magnitudes divided by the corresponding uncertainties (residual χ).