Jets from the Upper Scorpius Variable Young Star System 2MASS J16075796-2040087 Via KECK/HIRES Spectro-astrometry

TL;DR

This study investigates the jets and outflows from the young star 2MASS J16075796-2040087 in Upper Scorpius, revealing complex jet structures and challenging the presence of a traditional MHD disk wind, with implications for star-disk interactions.

Contribution

It provides detailed spectro-astrometric analysis of FELs, identifying jet components and questioning the existence of a classic MHD disk wind in a young star with accretion bursts.

Findings

The HVC traces an asymmetric bipolar jet ~700 au long.

The low-velocity emission resembles jet features and may originate from a slow jet near a close companion.

No clear evidence of a traditional MHD disk wind was found.

Abstract

2MASS J16075796-2040087 is a ~ 5 Myr young star in Upper Sco with evidence for accretion bursts on a timescale of about 15 days and, uncommonly for its age, outflows traced by multi-component forbidden emission lines (FELs). The accretion bursts may be triggered by a companion at ~ 4.6 au. We analyze HIRES spectra optimised for spectro-astrometry to better understand the origin of the several FEL velocity components and determine whether a MHD disk wind is present. The FEL high velocity component (HVC) traces an asymmetric, bipolar jet ~ 700 au long. The jet's position angle (PA) ~ 277 degrees is not perpendicular to the disk. The lower-velocity emission, classified previously as a disk wind low-velocity component (LVC), is found to have more in common with the HVC and overall it is not possible to identify a MHD disk wind component. The spectro-astrometric signal of the low velocity emission resembles those of jets and its density and ionisation fraction fall into the range of HVCs. We suggest a scenario where the accretion bursts due to the close companion power the jets past the age where such activity ends around most stars. The low-velocity emission here could come from a slow jet launched near the close companion and this emission would be blended with emission from the MHD wind.