Abstract
ABSTRACT Whilst ‘slingshot’ prominences have been observed on M-dwarfs, most if not all theoretical studies have focused on solar-like stars. We present an investigation into stellar prominences around rapidly rotating young M-dwarfs. We have extrapolated the magnetic field in the corona from Zeeman-Doppler maps and determined the sites of mechanical stability where prominences may form. We analyse the prominence mass that could be supported and the latitude range over which this material is distributed. We find that for these maps, much of this prominence mass may be invisible to observation – typically <1 per cent transits the stellar disc. On the rapidly rotating M-dwarf V374 Peg (Prot = 0.45 d) where prominences have been observed, we find the visible prominence mass to be around only 10 per cent of the total mass supported. The mass loss rate per unit area for prominences scales with the X-ray surface flux as $\dot{M}/A \propto \, F_\mathrm{ X}^{1.32}$ that is very close to the observationally derived value for stellar winds. This suggests that prominence ejection may contribute significantly to the overall stellar wind loss and spin-down. A planet in an equatorial orbit in the habitable zone of these stars may experience intermittent enhancements of the stellar wind due to prominence ejections. On some stars, this may occur throughout 20 per cent of the orbit.
Highlights
Stellar prominences are condensations of coronal plasma supported by the stellar magnetic field
The mass loss rate associated with the prominences can be found by considering the flow of material along these closed prominence bearing loops, since this is the mechanism by which the prominence formation sites fill up
In (b) of Figure 5 we show the prominence mass loss rates per unit area that would be predicted from the visible mass
Summary
Stellar prominences are condensations of coronal plasma supported by the stellar magnetic field. Cameron & Robinson (1989) deduced that these features originate from material co-rotating with the star, close to or beyond the stellar co-rotation radius They explained these features as the presence of large condensations of hydrogen, supported by the strong magnetic fields found on such rapidly rotating, young stars. Villarreal D’Angelo et al (2019) showed that for a solar like star these prominences reach their maximum mass and lifetime once the star reaches the zero-age main-sequence but that on fast rotators these prominences could be supported up to an age of 800Myrs During this time they will be contributing to the mass and angular momentum loss to varying degrees. For young stars, where prominences are more massive than their solar counterparts, the accumulative mass loss rate from regular ejection of the supported prominences may not be negligible and could have consequences for the stellar evolution
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