11 New Transiting Brown Dwarfs and Very Low Mass Stars from TESS

TL;DR

This paper reports the discovery of 11 new transiting brown dwarfs and low-mass stars from TESS, providing insights into their formation, evolution, and the brown dwarf desert through follow-up observations and analysis of their properties.

Contribution

The study adds 11 new transiting brown dwarfs and low-mass stars, expanding the sample size to over 50, and offers new perspectives on their formation mechanisms and the brown dwarf desert.

Findings

Sample size of confirmed transiting brown dwarfs exceeds 50.

Eccentricity distribution does not support a mass transition at 42 M_J.

Metallicity distribution does not indicate a clear formation boundary at 42 M_J.

Abstract

We present the discovery of 11 new transiting brown dwarfs and low-mass M-dwarfs from NASA's TESS mission: TOI-2844, TOI-3122, TOI-3577, TOI-3755, TOI-4462, TOI-4635, TOI-4737, TOI-4759, TOI-5240, TOI-5467, and TOI-5882. They consist of 5 brown dwarf companions and 6 very low mass stellar companions ranging in mass from $25 M_{\rm J}$ to $128 M_{\rm J}$. We used a combination of photometric time-series, spectroscopic, and high resolution imaging follow-up as a part of the TESS Follow-up Observing Program (TFOP) in order to characterize each system. With over 50 transiting brown dwarfs confirmed, we now have a large enough sample to directly test different formation and evolutionary scenarios. We provide a renewed perspective on the transiting brown dwarf desert and its role in differentiating between planetary and stellar formation mechanisms. Our analysis of the eccentricity distribution for the transiting brown dwarf sample does not support previous claims of a transition between planetary and stellar formation at $\sim42$ $M_{\rm J}$. We also contribute a first look into the metallicity distribution of transiting companions in the range $7 - 150$ $M_{\rm J}$, showing that this too does not support a $\sim42$ $M_{\rm J}$ transition. Finally, we also detect a significant lithium absorption feature in one of the brown dwarf hosts (TOI-5882) but determine that the host star is likely old based on rotation, kinematic, and photometric measurements. We therefore claim that TOI-5882 may be a candidate for planetary engulfment.