Issue |
A&A
Volume 650, June 2021
|
|
---|---|---|
Article Number | L20 | |
Number of page(s) | 10 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202140772 | |
Published online | 30 June 2021 |
Letter to the Editor
Large closed-field corona of WX Ursae Majoris evidenced from radio observations
1
ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, Dwingeloo 7991 PD, The Netherlands
e-mail: idavis@caltech.edu
2
Department of Physics and Astronomy, University of New Mexico, Albuquerque, USA
3
Kapteyn Astronomical Institute, University of Groningen, PO Box 72, 97200 AB Groningen, The Netherlands
4
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
5
School of Physics, Trinity College Dublin, the University of Dublin, Dublin-2, Ireland
6
LESIA, CNRS – Observatoire de Paris, PSL 92190 Meudon, France
7
Dublin Institute for Advanced Studies, Dublin, Ireland
8
Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
Received:
9
March
2021
Accepted:
29
April
2021
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 are specified, namely the plasma density in the outer corona and the radial distance at which the plasma forces the closed magnetic field into an open geometry. Low frequency radio observations (ν ≲ 200 MHz) of plasma and cyclotron emission from stars probe these magneto-ionic conditions. Here we report the detection of low-frequency (120–167 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 region extends to at least ≈10 stellar radii, which is about a factor of a few larger than the solar value, and possibly to ≳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 a lower plasma density and closed magnetic geometry.
Key words: stars: coronae / radio continuum: stars / plasmas / radiation mechanisms: non-thermal
© ESO 2021
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.