# Searching for chemical signatures of brown dwarf formation

## TL;DR

This study investigates the chemical signatures and formation mechanisms of brown dwarfs by analyzing stellar parameters and abundances in stars hosting brown dwarf companions, revealing different formation pathways for massive and low-mass brown dwarfs.

## Contribution

It provides new insights into the formation mechanisms of brown dwarfs, highlighting differences in metallicity and abundance patterns between massive and low-mass brown dwarf hosts.

## Key findings

- Stars with massive brown dwarfs have similar metallicity to stars without planets.
- Stars with less-massive brown dwarfs tend to have slightly higher metallicity.
- Massive and low-mass brown dwarfs show differences in orbital period and eccentricity.

## Abstract

Recent studies have shown that close-in brown dwarfs in the mass range 35-55 M$_{\rm Jup}$ are almost depleted as companions to stars, suggesting that objects with masses above and below this gap might have different formation mechanisms. We determine the fundamental stellar parameters, as well as individual abundances for a large sample of stars known to have a substellar companion in the brown dwarf regime. The sample is divided into stars hosting "massive" and "low-mass" brown dwarfs. Following previous works a threshold of 42.5 M$_{\rm Jup}$ was considered. Our results confirm that stars with brown dwarf companions do not follow the well-established gas-giant planet metallicity correlation seen in main-sequence planet hosts. Stars harbouring "massive" brown dwarfs show similar metallicity and abundance distribution as stars without known planets or with low-mass planets. We find a tendency of stars harbouring "less-massive" brown dwarfs of having slightly larger metallicity, [X$_{\rm Fe}$/Fe] values, and abundances of Sc II, Mn I, and Ni I in comparison with the stars having the massive brown dwarfs. The data suggest, as previously reported, that massive and low-mass brown dwarfs might present differences in period and eccentricity. We find evidence of a non-metallicity dependent mechanism for the formation of massive brown dwarfs. Our results agree with a scenario in which massive brown dwarfs are formed as stars. At high-metallicities, the core-accretion mechanism might become efficient in the formation of low-mass brown dwarfs while at lower metallicities low-mass brown dwarfs could form by gravitational instability in turbulent protostellar discs.