On the Radii of Brown Dwarfs Measured with AKARI Near-Infrared Spectroscopy

TL;DR

This study measures the radii of 16 brown dwarfs using AKARI near-infrared spectroscopy, revealing a minimum radius at mid-to late-L spectral types and confirming theoretical models of brown dwarf evolution.

Contribution

It provides new empirical radius measurements for brown dwarfs and identifies a radius minimum at specific temperatures, supporting existing theoretical models.

Findings

Brown dwarf radii range from 0.64 to 1.13 RJ.

Radius minimum occurs at Teff~1600 K.

Results align with theoretical radius-mass and radius-age relations.

Abstract

We derive the radii of 16 brown dwarfs observed by AKARI using their parallaxes and the ratios of observed to model fluxes. We find that the brown dwarf radius ranges between 0.64-1.13 RJ with an average radius of 0.83 RJ. We find a trend in the relation between radii and Teff; the radius is at a minimum at Teff~1600 K, which corresponds to the spectral types of mid-to late-L. The result is interpreted by a combination of radius-mass and radius-age relations that are theoretically expected for brown dwarfs older than 10^8 yr.