Spitzer IRS Spectra of Young Stars Near the Hydrogen Burning Mass Limit

We present Spitzer Infrared Spectrograph* (IRS) measurements for two young stars in the Taurus star-forming region, with masses near the hydrogen-burning mass limit . While one of the objects displays no mid-infrared excess, the other one shows a large excess at wavelengths longward of 10 microns. The latter spectrum resembles in detail the spectra of flared, optically-thick accretion disks around more massive classical T Tauri stars. A bright and complex 10 micron silicate emission feature in this spectrum indicates the presence in the disk photosphere of small dust grains that contain significant amounts of crystalline silicates.

This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through Contract Number 1257184 issued by JPL/Caltech, and Cornell subcontracts 31419-5714 to the University of Rochester.

* The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation funded by NASA through the Jet Propulsion Laboratory and the Ames Research Center.