The rotation of brown dwarfs

TL;DR

Brown dwarfs tend to remain fast rotators over gigayear timescales, unlike low-mass stars, with observational evidence suggesting limited angular momentum loss mechanisms in the substellar regime.

Contribution

This review summarizes observational evidence for rapid rotation in brown dwarfs and discusses implications for angular momentum evolution and planetary spin-mass relations.

Findings

Brown dwarfs generally retain high rotation rates over long timescales.

Angular momentum loss mechanisms are less effective in brown dwarfs compared to stars.

Fast rotation in brown dwarfs links to planetary spin-mass relations.

Abstract

One of the characteristic features of low-mass stars is their propensity to shed large amounts of angular momentum throughout their evolution. This distinguishs them from brown dwarfs which remain fast rotators over timescales of gigayears. Brown dwarfs with rotation periods longer than a couple of days have only been found in star forming regions and young clusters. This is a useful constraint on the mass dependency of mechanisms for angular momentum regular in stars. Rotational braking by disks and winds become highly inefficient in the substellar regime. In this short review I discuss the observational evidence for the fast rotation in brown dwarfs, the implications, and the link to the spin-mass relation in planets.