# Orion Source I's disk is salty

## TL;DR

This study reports the first detection of salty molecules NaCl and KCl, including their vibrationally excited states, in the disk around Orion SrcI, revealing insights into the disk's composition, excitation mechanisms, and potential as a diagnostic tool.

## Contribution

It is the first detection of NaCl and KCl molecules and their vibrationally excited states in the interstellar medium outside evolved star ejecta, providing new insights into high-mass protostellar disks.

## Key findings

- Detected NaCl and KCl molecules and their isotopologues in Orion SrcI disk.
- First observation of vibrationally excited states of these molecules in the ISM.
- Vibrational states likely excited radiatively via mid-infrared transitions.

## Abstract

We report the detection of NaCl, KCl, and their $^{37}$Cl and $^{41}$K isotopologues toward the disk around Orion SrcI. About 60 transitions of these molecules were identified. This is the first detection of these molecules in the interstellar medium not associated with the ejecta of evolved stars. It is also the first ever detection of the vibrationally excited states of these lines in the ISM above v = 1, with firm detections up to v = 6. The salt emission traces the region just above the continuum disk, possibly forming the base of the outflow. The emission from the vibrationally excited transitions is inconsistent with a single temperature, implying the lines are not in LTE. We examine several possible explanations of the observed high excitation lines, concluding that the vibrational states are most likely to be radiatively excited via rovibrational transitions in the 25-35 {\mu}m (NaCl) and 35-45 {\mu}m (KCl) range. We suggest that the molecules are produced by destruction of dust particles. Because these molecules are so rare, they are potentially unique tools for identifying high-mass protostellar disks and measuring the radiation environment around accreting young stars.