اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLarge closed-field corona of WX UMa evidenced from radio observations
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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 ($ u 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 UMas 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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