# Double-peaked OI profile: a likely signature of the gaseous ring around KH 15D

## TL;DR

This paper interprets the double-peaked [O I] emission profiles of KH 15D as evidence of a gaseous ring at 0.5-5 au, likely truncated by external UV radiation, supporting the presence of a circumbinary dust ring.

## Contribution

It provides a new interpretation of emission line profiles as originating from a gaseous ring, linking spectroscopic features to the physical structure of KH 15D's circumbinary disk.

## Key findings

- Emission radii between 0.5 and 5 au were measured.
- The gaseous ring is similar in extent to the dust ring inferred from photometry.
- External UV photoevaporation may have truncated the disk.

## Abstract

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~{\scriptsize I}]\,$\lambda$6300 profiles as originating from the hot disk surface of KH 15D. By modeling these profiles, we measure emitting radii between $\sim$0.5--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 UV photons from the nearby massive star HD~47887 has truncated the outer edge of the disk to the observed value.