High-sensitivity radio study of the non-thermal stellar bow shock EB27

TL;DR

This study provides a detailed radio-polarimetric analysis of the stellar bow shock EB27, revealing non-thermal emission characteristics, magnetic field constraints, and refined system parameters, enhancing understanding of stellar bow shocks.

Contribution

It presents the first polarimetric observations of EB27's non-thermal radio emission and models the magnetic field and electron acceleration in this unique stellar bow shock.

Findings

No significant linear polarisation detected above 0.5%.

Diffuse emission is steeper and brighter than previously observed.

Refined system parameters place EB27's origin in Cyg OB2.

Abstract

We present a deep radio-polarimetric observation of the stellar bow shock EB27 associated to the massive star BD+43 3654. This is the only stellar bow shock confirmed to have non-thermal radio emission. We used the Jansky Very Large Array in S band (2 - 4GHz) to test whether this synchrotron emission is polarised. The unprecedented sensitivity achieved allowed us to map even the fainter regions of the bow shock, revealing that the more diffuse emission is steeper and the bow shock brighter than previously reported. No linear polarisation is detected in the bow shock above 0.5%, although we detected polarised emission from two southern sources, probably extragalactic in nature. We modeled the intensity and morphology of the radio emission to better constrain the magnetic field and injected power in relativistic electrons. Finally, we derived a set of more precise parameters for the system EB27-BD+43 3654 using Gaia Early Data Release 3, including the spatial velocity. The new trajectory, back in time, intersects the core of the Cyg OB2 association.