# Extremely high excitation SiO lines in disk-outflow system in Orion Source I

## TL;DR

This study uses ALMA to detect and analyze high-excitation SiO lines in Orion Source I, revealing details about the disk-outflow system and estimating the central mass of the young stellar object.

## Contribution

First detection of SiO v=4 line in a star-forming region, providing new insights into the disk-outflow dynamics of Orion Source I.

## Key findings

- Detected SiO v=4 J=11-10 line for the first time in star-forming regions.
- Identified compact SiO emission structures associated with the outflow base and disk surface.
- Estimated the central mass of the object to be at least 7 solar masses.

## Abstract

We present high-resolution images of the submillimeter SiO line emissions of a massive young stellar object Orion Source I using the Atacama Large Millimeter/ Submillimeter Array (ALMA) at band 8. We detected the 464 GHz SiO v=4 J=11-10 line in Source I, which is the first detection of the SiO v=4 line in star-forming regions, together with the 465 GHz 29SiO v=2 J=11-10 and the 428 GHz SiO v=2 J=10-9 lines with a resolution of 50 AU. The 29SiO v=2 J=11-10 and SiO v=4 J=11-10 lines have compact structures with the diameter of <80 AU. The spatial and velocity distribution suggest that the line emissions are associated with the base of the outflow and the surface of the edge-on disk. In contrast, SiO v=2 J=10-9 emission shows a bipolar structure in the direction of northeast-southwest low-velocity outflow with ~200 AU scale. The emission line exhibits a velocity gradient along the direction of the disk elongation. With the assumption of the ring structure with Keplerian rotation, we estimated the lower limit of the central mass to be 7 solar mass and the radius of 12 AU< r <26 AU.