2019ApJ...879L..10F

KH 15D is a well-known spectroscopic binary because of its unique and dramatic photometric variability. The variability is explained by a circumbinary dust ring, but the ring itself was never directly detected. We present a new interpretation of the double-peaked [O I] λ6300 profiles as originating from the hot disk surface of KH 15D. By modeling these profiles, we measure emitting radii between ∼0.5 and 5 au, basically a gaseous ring very similar in radial extent to the dust ring inferred from modeling the system's photometric variability. We also discuss the possibility that external photoevaporation driven by ultraviolet photons from the nearby massive star HD 47887 has truncated the outer edge of the disk to the observed value.