The Li dip : a probe of angular momentum transport in low mass stars

TL;DR

This study investigates how angular momentum transport mechanisms affect lithium depletion in low-mass stars, using models that incorporate rotation-induced mixing and element segregation, to explain the Li dip observed in Hyades stars.

Contribution

It demonstrates that wind-driven meridian circulation and shear turbulence can explain the Li dip, highlighting the need for an additional mechanism on the cool side.

Findings

The hot side of the Li dip is explained by current models.

An additional angular momentum transport mechanism is needed on the cool side.

The same mechanism may explain the Sun's flat rotation profile.

Abstract

We use the measures of Li and rotational velocities in F Hyades stars to assess the role of the wind-driven meridian circulation and of shear turbulence in the transport of angular momentum in stars of different masses. Our models include both element segregation and rotation-induced mixing, and we treat simultaneously the transport of matter and angular momentum as described by Zahn (1992) and Maeder (1995). We show that the hot side of the Li dip in the Hyades is well explained within this framework, which was also successfully used to reproduce the C and N anomalies in B type stars (Talon et al. 1997). On the cool side of the dip, another mechanism must participate in the transport of angular momentum; its efficiency is linked to the depth of the surface convection zone. That mechanism should also be responsible for the Sun's flat rotation profile.