Slingshot prominences: nature's wind gauges

TL;DR

This paper introduces a novel method to measure mass loss rates in young, rapidly-rotating stars using observations of slingshot prominences, providing insights into stellar wind properties and their relation to X-ray flux.

Contribution

It presents a new observational technique leveraging prominence data to estimate stellar wind mass loss rates, extending the known relationship with X-ray flux.

Findings

Mass loss rates can be estimated from prominence observations.

No evidence of weakening mass loss at high X-ray flux levels.

Method extends the mass loss rate–X-ray flux relationship over five orders of magnitude.

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.