Outflow from the very massive Wolf-Rayet binary Melnick 34

TL;DR

This study uses high-resolution optical spectroscopy to reveal an outflow from the massive Wolf-Rayet binary Melnick 34, demonstrating its influence on the surrounding interstellar medium and suggesting periodic activity linked to its X-ray behavior.

Contribution

First spatially resolved optical spectroscopic analysis of the ISM around Melnick 34, identifying a cone-like outflow structure and linking it to the binary's periodic X-ray activity.

Findings

Detected a cone-like outflow structure from Melnick 34

Observed increased extinction towards the R136 cluster

Residual variations may be linked to the binary's 155-day cycle

Abstract

Melnick 34 (Mk 34) is one of the most massive binary systems known and is one of the brightest X-ray point sources in the 30 Doradus region. We investigated the impact of this massive system on the surrounding interstellar medium (ISM) using the optical spectroscopic capabilities of the narrow-field mode (NFM) of the Multi-Unit Spectroscopic Explorer (MUSE). MUSE-NFM spatially resolved the ISM in the vicinity of Mk 34 with a resolution comparable to that of the HST. The analysis of the [NII]$\lambda$6583 and [SII]$\lambda$6717 emission lines reveals a cone-like structure apparently originating from Mk 34 and extending southeast. Electron density maps and radial velocity measurements of the ISM lines further support an outflow scenario traced by these emissions. While no clear northwestern counterpart to this outflow was observed, we note increased extinction in that direction, towards the R136 cluster. The ISM material along the projected diagonal of the outflow on both sides of Mk 34 shows similar properties in terms of the emission line ratios seen in the Baldwin-Phillips-Terlevich diagram. These results are consistent across two observational epochs. Additionally, we examined the residual maps within a 0.5" radius of Mk 34 after modeling and subtracting the point spread function. The observed variations in the residuals could potentially be linked to Mk 34's known periodic behavior. However, further observations with appropriate cadence are needed to fully monitor the 155 day periodicity of Mk 34's X-ray emissions.