Predicting the mass loss rates of Mdwarfs

Prominences, cool condensations of coronal plasma, have been observed on many types of star. Rapidly rotating stars are known to show “slingshot prominences”, that form multiple stellar radii above the surface. Models of these features typically focus on solar type stars, especially the prototype AB Doradus. 

Here we model the “prominence formation sites” around a sample of rapidly rotating M-dwarfs. Using Zeeman Doppler Imaging (ZDI) maps of our stellar sample, the magnetic field structure within the corona can be constructed, assuming a potential field. We define “prominence formation sites” as locations of stable equilibrium within the constructed field topologies, which are found via modelling of the ZDI maps. We use the mass loss rates per unit area (Mdot/A) of the modelled prominences to predict this same quantity for the stellar wind, by assuming that the same mechanism of an isothermal up flow feeds both events.

We find that all stars in our sample show prominence formation sites, suggesting that prominences are common features on these stars. We plot the prominence mass loss rates per unit area on Wood’s plot of (Mdot/A) versus stellar X-ray flux and find our line of best fit (Mdot/A proportional to 1.32) matches well with previously published relations. We also show that due to the inclination at which we view these stars, many prominences would not cross the stellar disc from our line of sight and therefore would not be found by observational methods, greatly underestimating the true mass loss rate.