Differential rotation of main-sequence dwarfs: predicting the dependence on surface temperature and rotation rate

TL;DR

This paper predicts how the surface differential rotation of main-sequence dwarf stars depends on observable parameters like temperature and rotation period, confirming that hotter stars exhibit greater differential rotation, especially among late F-stars.

Contribution

It introduces a theoretical model linking differential rotation to surface temperature and rotation period, simplifying previous models with fewer parameters and providing an analytical approximation.

Findings

Differential rotation increases with surface temperature.

Late F-stars show a steeper increase in differential rotation.

Maximum differential rotation occurs at intermediate rotation rates.

Abstract

Gyrochronology and recent theoretical findings are used to reduce the number of input parameters of differential rotation models. This eventually leads to a theoretical prediction for the surface differential rotation as a function of only two stellar parameters - surface temperature and rotation period - that can be defined observationally. An analytical approximation for this function is suggested. The tendency for the differential rotation to increase with temperature is confirmed. The increase is much steeper for late F-stars compared to G- and K-dwarfs. Slow and fast rotation regimes for internal stellar rotation are identified. A star attains its maximum differential rotation at rotation rates intermediate between these two regimes. The amplitude of the meridional flow increases with surface temperature and rotation rate. The structure of the flow changes considerably between cases of slow and fast rotation. The flow in rapid rotators is concentrated in the boundary layers near the top and bottom of the convection zone with very weak circulation in between.