Best-fit XTGRID with WD model to the VLT/X-shooter spectrum of J2102−4145 at orbital phase ϕ = 0.25 (maximum radial velocity difference) in the rest frame of the secondary. The observed spectrum can be reproduced by two nearly identical WD components (red and blue lines). At ϕ = 0.25 and 0.75, the components show the largest radial velocity difference and the double absorption core of the Hα reveals the binarity (inset). The phase-resolved spectral coverage for the entire orbit is available in Fig. 3.