Mean spectrum of TIC 378898110, combining 49 one-minute spectra obtained using Goodman + SOAR on 2021 July 05. Visible features are marked. All tick marks below the spectrum refer to He i. For comparison, we also plot a synthetic, 14 000 K, log g = 8.0, helium-atmosphere white dwarf spectrum (grey, dashed) from Cukanovaite et al. (2021) scaled to the same mean flux and offset by −3.5 mJy.