Accretion and Outflow Activity in Brown Dwarfs

TL;DR

This paper reviews observational evidence of accretion and outflow activities in brown dwarfs and very low-mass stars, highlighting their similarities to star formation processes and recent advances with new instruments.

Contribution

It summarizes current observational techniques and findings on accretion and outflow in brown dwarfs, emphasizing the role of new instruments like VLT/X-Shooter.

Findings

Accretion characteristics are continuous across the sub-stellar boundary.

Outflow activity has been confirmed via spectro-astrometry and millimeter imaging.

Recent instruments enable broader wavelength studies of these phenomena.

Abstract

An investigation of the magnetospheric accretion and outflow signatures in sub-stellar objects is a natural extension of similar studies conducted on classical T Tauri stars (CTTS), and helps understand if brown dwarfs (BDs) follow the same formation mechanism as stars. Over the past decade, evidence for accretion in very low-mass stars (VLMs) and BDs has been accumulated using various techniques, which indicates that the overall accretion characteristics are continuous across the sub-stellar boundary. Outflow activity in VLMs and BDs has been confirmed based on spectro-astrometry of forbidden emission lines observed in the optical, and in millimetre continuum images of CO J=2-1 emission. This review summarizes the past and current state of observational work on accretion and outflow activity in VLMs and BDs, particularly with the advent of new instruments such as VLT/X-Shooter which has allowed the study of several accretion and outflow indicators over a wider wavelength range.