DOI

https://doi.org/10.48717/1y80-rj63

Project

EB089

Title

EB089 firsth epoch WX UMa Astrometry

Abstract

WX UMa is a known radio flare star (M6.0V) at only 4.9 pc distance. In our recent EVN project EB082 we have achieved a strong detection (1.2 mJy) of polarized emission (63% LCP). Intriguingly, our analysis shows the radio source to be offset by 6.5 mas (0.032 au) from the location as predicted from Gaia DR2 and EDR3 positional and proper motion data. Therefore, the emission appears to originate from outside the coronal envelope of the star, an unprecedented conclusion which suggests the presence of a sub-stellar companion driving the emission. The emission is strongly circularly polarized as expected for the ECMI mechanism that would drive such radiation. We request three follow-up observations to conclusively establish the offset using multiple phase reference targets (MultiView) and to perform astrometric determination of the position and motion of the emission. We will also schedule polarization calibration targets to ensure polarimetric accuracy of the data, which together with our measurements of brightness, variability and motion should allow us to characterize the nature of this emission, and the underlying engine powering it.