Brown Dwarf Disks at Ages of 5-10 Myr

TL;DR

This study investigates the properties and composition of brown dwarf disks in the 5-10 million-year-old Upper Scorpius region using infrared observations, revealing a low disk fraction and evidence of disk evolution.

Contribution

It provides new observational data on brown dwarf disks at 5-10 Myr, including disk fraction, structure, and composition, and discusses their evolution and potential lifetimes.

Findings

Disk fraction of 10.7% in Upper Scorpius

Detection of silicate emission features indicating disk composition

Observation of flat disk structures at this age

Abstract

We present Spitzer/IRAC and MIPS 24mu archival observations for 28 brown dwarfs in the Upper Scorpius (UppSco) region. We find a disk fraction of 10.7%^(+8.7%)_(-3.3%). One object shows a small excess at 24mu but none at shorter wavelengths, and may be a candidate transition disk. Three objects show emission in the 10mu silicate feature and we present compositional fits for these sources. Flat structures are observed for all disk sources in UppSco. Also presented are the MIPS/70mu observations for the TW Hydrae Association brown dwarf 2MASS J1139511-315921. We discuss the structure and chemistry of brown dwarf disks at ages of ~5-10 Myr, and consider the possible effects of the brown dwarf densities in these clusters on the disk lifetimes.