Angular momentum and disk evolution in very low mass systems

TL;DR

This review discusses how brown dwarfs evolve in terms of angular momentum and disks, showing they remain fast rotators after 10 Myr and have scaled-down disks, implying potential for planetary system formation.

Contribution

It provides a comprehensive summary of recent observational results on brown dwarf disk properties and rotational evolution, highlighting differences from stellar counterparts.

Findings

Brown dwarfs beyond 10 Myr are fast rotators and do not spin down.

Brown dwarf disks are scaled-down versions of stellar disks with similar properties.

Disk evolution timescales in brown dwarfs are consistent with those in stars.

Abstract

This review summarises recent observational results regarding the evolution of angular momentum and disks in brown dwarfs. The observations clearly show that brown dwarfs beyond ages of 10 Myr are exclusively fast rotators and do not spin down with age. This suggests that rotational braking by magnetic winds becomes very inefficient or ceases to work in the substellar regime. There is, however, some evidence for braking by disks during the first few Myrs in the evolution, similar to stars. Brown dwarf disks turn out to be scaled down versions of circumstellar disks, with dust settling, grain growth, and in some cases cleared out inner regions. The global disk properties roughly scale with central object mass. The evolutionary timescales in substellar disks are entirely consistent with what is found for stars, which may be challenging to understand. Given these findings, it is likely that brown dwarfs are able to form miniature planetary systems.