Spatially Resolved Mid-IR Imaging of the SR 21 Transition Disk

TL;DR

This study uses mid-IR imaging to resolve dust structures in the SR 21 transition disk, revealing a larger cleared inner region than previously modeled and proposing a new disk configuration with a warm companion.

Contribution

It provides the first spatially resolved mid-IR observations of SR 21, challenging previous models and suggesting a new disk structure with a large inner hole and a potential warm companion.

Findings

Disk is completely cleared within ~10 AU.

Previous models with hot inner disk are inconsistent with data.

A large inner hole with a warm companion best fits the observations.

Abstract

We present mid-IR observations from Gemini/TReCS that spatially resolve the dust emission around SR 21. The protoplanetary disk around SR 21 is believed to have a cleared gap extending from stellocentric radii of ~0.5 AU to ~20 AU, based on modeling of the observed spectral energy distribution. Our new observations resolve the dust emission, and our data are inconsistent with the previous model. We require the disk to be completely cleared within ~10 AU, without the hot inner disk spanning ~0.25-0.5 AU posited previously. To fit the SED and mid-IR imaging data together, we propose a disk model with a large inner hole, but with a warm companion--possibly surrounded by circumstellar material of its own--residing near the outer edge of the cleared region. We also discuss a model with a narrow ring included in a large cleared inner disk region, and argue that it is difficult to reconcile with the data.