Slingshot prominences: nature's wind gauges. Issue 3 (24th October 2018)

• Record Type: Journal Article
• Authors: Jardine, Moira; Collier Cameron, Andrew
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 482:Issue 3(2019)
• Page Start: 2853
• Page End: 2860
• Publication Date: 2018-10-24
• Subjects: stars: coronae -- stars: late-type -- stars: magnetic field -- stars: mass-loss -- stars: rotation -- stars: winds, outflows; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty2872
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Mass-loss rates for the tenuous, hot winds of cool stars are extremely difficult to measure, yet they are a crucial ingredient in the stars' rotational evolution. We present a new method for measuring these mass-loss rates in young, rapidly rotating stars. These stars are known to support systems of 'slingshot prominences' fed by hot wind material flowing up from the stellar surface into the summits of closed magnetic loop structures. The material gathers and cools near the co-rotation radius until its density becomes large enough that it is visible as a transient absorption feature in the hydrogen Balmer lines and strong resonance lines such as Ca ii H & K. Here we present the key insight that the sonic point usually lies well below the condensation region. The flow at the wind base is therefore unaffected by the presence of an overlying prominence, so we can use the observed masses and recurrence times of the condensations to estimate the mass flux in the wind. These measurements extend the relationship between mass-loss rate per unit surface area and X-ray flux to span 5 orders of magnitude. They demonstrate no evidence of the suspected weakening of stellar mass-loss rates at high X-ray flux levels.