Evidence of Radius Inflation Based on 50 Transiting Brown Dwarfs and Low-mass Stellar Companions

TL;DR

This study confirms that many transiting brown dwarfs exhibit radius inflation, especially at close separations, supporting the idea that stellar irradiation influences their sizes.

Contribution

The paper provides the first population-level evidence of radius inflation in transiting brown dwarfs, with detailed analysis of factors like separation and temperature.

Findings

8.7% average radius inflation across the sample

Higher inflation (16%) at separations ≤ 0.05 au

Inflation decreases with increasing separation

Abstract

Statistical assessment of stellar parameters enables validation and improvements in theoretical models. We compiled a sample of 85 transiting stellar and substellar companions, with masses ranging from $\sim$13-100 $M_\mathrm{Jup}$. We focus on analyzing 50 transiting companions with robust ages and model constraints, and evaluate the degree of radius inflation versus mass, separation, equilibrium temperature, and metallicity. Our evaluation of the differences between measured and model radii indicates an $8.7\pm1.9$% radius inflation for the full sample, at $4.6\sigma$ discrepancy, validating the existence of radius inflation at a population level in transiting brown dwarfs. For brown dwarfs at separations $\leq 0.05$ au, we find an even higher radius inflation, with a median inflation of $16\pm6$% at $2.7\sigma$, and the inflation decreases toward wider separations, likely due to reduced stellar irradiation. Finally, we provide our compilation for the community to use.