Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf

TL;DR

This study reports on the observation and modeling of an edge-on circumstellar disk around a young brown dwarf, revealing its structure, inclination, and evidence of a transition disk with a large inner hole, using Hubble, Spitzer, and ground-based data.

Contribution

First detailed multi-wavelength observational analysis and modeling of an edge-on circumstellar disk around a brown dwarf, including disk inclination and structure.

Findings

Disk inclination is approximately 70 degrees from face-on.

The disk contains a large inner hole (~58 R_star), indicating a transition disk.

The disk size exceeds predictions from embryo ejection models.

Abstract

We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosphere reddened by normal extinction. Instead, the slope is consistent with scattered light, indicating that circumstellar material is occulting the brown dwarf. By combining the SpeX data with mid-IR photometry and spectroscopy from the Spitzer Space Telescope and previously published millimeter data from Scholz and coworkers, we construct the spectral energy distribution for 2MASS J04381486+2611399 and model it in terms of a young brown dwarf surrounded by an irradiated accretion disk. The presence of both silicate absorption at 10 um and silicate emission at 11 um constrains the inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional evidence of the high inclination of this disk is provided by our detection of asymmetric bipolar extended emission surrounding 2MASS J04381486+2611399 in high-resolution optical images obtained with the Hubble Space Telescope. According to our modeling for the SED and images of this system, the disk contains a large inner hole that is indicative of a transition disk (R_in~58 R_star~0.275 AU) and is somewhat larger than expected from embryo ejection models (R_out=20-40 AU vs. R_out<10-20 AU).