Extended Data Fig. 7: Observed spectral energy distribution for WD0032–317 compared to the best-fitting composite theoretical model spectra of a white dwarf and a black body/brown dwarf.
The archival GALEX ultraviolet photometry, where the contribution from the companion is negligible, appears as blue square-shaped error bars. Minimal/maximal photometric values in different bands, extracted from the light curves, appear as green-shades circle-shaped error bars for LCOGT’s r′, i′, and z bands, and as red-shades diamond-shaped error bars for the WISE W1 band. A theoretical model spectrum of a hydrogen-dominated white dwarf with an effective temperature of 37,000K and a surface gravity log g=7.263 is shown in dashed light blue. The best-fitting brown-dwarf (64,65; for the night side, with [M/H] = -0.5 (He) or [M/H] = -1.0 (hybrid) and log g = 5.5) and black-body (for the day side) models are plotted in solid purple and dotted orange, respectively. The theoretical spectra were scaled using the system’s distance measured by the Gaia mission, and the estimated component radii (left: assuming a helium-core white dwarf (He), right: assuming a ‘hybrid’ carbon-oxygen core white dwarf with a thick helium envelope). The brown-dwarf model is shown multiplied by a factor of 4, to fit the displayed range. The composite model of the system at orbital phase 0 (0.5) is plotted in solid dark grey (black). The units shown on the y axis are the flux per wavelength, λ, multiplied by λ4, for visual clarity. The bottom panels show the residuals of the day-side (middle) and the night-side (bottom) fits. The error bars in the residual plots show the standard deviation and take into account both the photometric and the model uncertainties.
