Modeling of the magnetic stellar wind braking of the ssrAp 33 Lib (HD137949)

TL;DR

This paper models magnetic stellar wind braking in the star 33 Lib, demonstrating its role in stellar spin-down and providing a method to estimate stellar mass-loss rates.

Contribution

It introduces a numerical model of magnetic braking using MESA, accounting for magnetic field evolution and wind, and defines a parameter to quantify braking significance.

Findings

Stars with rotation periods up to 80 years can form due to magnetic braking.

The method allows estimation of mass-loss rates for moderate-mass stars.

The dimensionless parameter $$ indicates when braking is significant.

Abstract

Using the ssrAp star 33 Lib (HD137949) as an example, we show that magnetic braking caused by the interaction of a strong magnetic field with a stellar wind can play a key role in slowing the rotation of ssrAp stars. Numerical modeling of stellar rotation spin-down in the MESA package, taking into account the evolution of magnetic fields and the stellar wind, shows that stars with rotation periods of up to 80 years and longer can form. Moreover, braking by a magnetized wind makes it possible to estimate the mass-loss rate for stars of moderate mass ($1.25 M_\odot < M < 2 M_\odot$), which is difficult to do by other methods. We introduce the dimensionless parameter $\Xi$, which reflects the spin-down time and the stellar lifetime. Thus, when $\Xi \gg 1$, braking is important, whereas when $\Xi \ll 1$, it is negligible.