# Water and OH Emission from the inner disk of a Herbig Ae/Be star

## TL;DR

This paper reports the first detection of hot water and hydroxyl emission from the inner disk of a Herbig Ae/Be star, revealing insights into the molecular composition and physical conditions of the disk.

## Contribution

It presents the first detection of water emission near 2.9 μm from a Herbig Ae/Be star and analyzes the molecular emission as cospatial, linking it to the star's high inclination and dust-depleted inner disk.

## Key findings

- Detection of hot H₂O and OH emission from HD 101412
- Molecules are consistent with being cospatial in the disk
- Inner disk likely dust-depleted, allowing deeper molecular probing

## Abstract

We report the detection of hot H$_{2}$O and OH emission from the Herbig Ae/Be star HD$~101412$ using the Cryogenic Infrared Echelle Spectrograph on the $\textit{Very Large Telescope}$. Previous studies of Herbig Ae/Be stars have shown the presence of OH around some of these sources, but H$_{2}$O has proven more elusive. While marginal water emission has been reported in the mid-infrared, and a few Herbig Ae/Be stars show water emission in the far-infrared, water emission near 2.9 $\mu$m has not been previously detected. We apply slab models to the ro-vibrational OH, H$_{2}$O, and CO spectra of this source and show that the molecules are consistent with being cospatial. We discuss the possibility that the detection of the CO overtone bandhead emission, detection of water emission, and the large line to continuum contrast of the OH lines may be connected to its high inclination and the $\lambda$ Bo\"o nature of this star. If the low abundance of refractories results from the selective accretion of gas relative to dust, the inner disk of HD$~101412$ should be strongly dust-depleted allowing us to probe deeper columns of molecular gas in the disk, enhancing its molecular emission. Our detection of C- and O-bearing molecules from the inner disk of HD$~101412$ is consistent with the expected presence in this scenario of abundant volatiles in the accreting gas.