GRAVITY data for WR 78, a single WN7h star, along with the best-fit model shown in red. The top left panel shows the u-v coverage for the observation. The remaining panels, from left to right, show NFLUX, T3PHI, DPHI and |V| respectively, color-coded according to baselines. The data are zoomed in to a wavelength range of around 2.09–2.21 μm, with three strong emission lines present around 2.11, 2.16 and 2.19 μm. The |V| data show clear features corresponding to the first two spectral lines, decreasing in prominence from longer to shorter baselines. The best-fit model for such a system is an unresolved point source emitting the 2.19 μm spectral line and a slightly resolved Gaussian (fwhm ≈ 0.51 ± 0.02 mas) emitting the 2.11 and 2.16 μm spectral lines.