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arXiv · 2105.01021

Large closed-field corona of WX UMa evidenced from radio observations

I. Davis·H. K. Vedantham·J. R. Callingham·T. W. Shimwell·A. A. Vidotto·P. Zarka·T. P. Ray·A. Drabent
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Abstract

The space-weather conditions that result from stellar winds significantly impact the habitability of exoplanets. The conditions can be calculated from first principles if the necessary boundary conditions -- namely on the plasma density in the outer corona and the radial distance at which the plasma forces the closed magnetic field into an open geometry -- are specified. Low frequency radio observations ($\nu \lesssim 200$ MHz) of plasma and cyclotron emission from stars probe these magneto-ionic conditions. Here we report the detection of low-frequency ($120-167\,{\rm MHz}$) radio emission associated with the dMe6 star WX UMa. If the emission originates in WX UMa's corona, we show that the closed field regions extends to at least $\approx 10$ stellar radii, that is about a factor of a few larger than the solar value, and possibly to $\gtrsim 20$ stellar radii. Our results suggest that the magnetic-field structure of M dwarfs is in between Sun-like and planet-like configurations, where compact over-dense coronal loops with X-ray emitting plasma co-exist with a large-scale magnetosphere with lower plasma density and closed magnetic geometry.

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I. Davis, H. K. Vedantham, J. R. Callingham, T. W. Shimwell, A. A. Vidotto, P. Zarka, T. P. Ray, A. Drabent. 2021-05-03. Large closed-field corona of WX UMa evidenced from radio observations. https://doi.org/10.1051/0004-6361%2F202140772

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