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W.J. Forrest, B. Sargent (U. Rochester), E. Furlan (Cornell U.), C.H. Chen (JPL), F. Kemper (UCLA), N. Calvet, L. Hartmann (CfA), K.I. Uchida (Cornell U.), D.M. Watson, J.D. Green (U. Rochester), L.D. Keller (Ithaca College), G.C. Sloan, T.L. Herter (Cornell U.), B.R. Brandl (Leiden U.), J.R. Houck, D.J. Barry, P. Hall (Cornell U.), P.W. Morris (SSC), J. Najita (NOAO), P.C. Myers (CfA), P. D'Alessio (CRYA UNAM), M. Jura (UCLA)
We present the first Spitzer Infrared Spectrograph* observations of the disks around classical T Tauri stars: spectra in the 5.3-30 micron range of six stars that appear not to be members of close binary systems. The spectra are dominated by emission features from amorphous silicate dust, and a continuous component from 5 to 8 microns that in most cases comprises an excess above the photosphere throughout our spectral range. There is considerable variation in the silicate feature/continuum ratio, which implies variations of inclination, disk flaring, and stellar mass accretion rate. In some of our stars, structure in the silicate feature suggests the presence of a crystalline component, somewhat surprising for objects this young (1-2 Myr). In one, CoKu Tau 4, no excess above the photosphere appears at wavelengths shortward of the silicate features, similar to 10 Myr old TW Hya, TWA 3 and HR 4796A. This indicates a truncation of the inner the disk, a feature suggestive of gravitational influence by planets or close stellar companions; CoKu Tau 4 would be the first star in the million-year-old age range in which such a central clearing is found.
* 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.
This work is based [in part] 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.
Support for this work was provided by NASA through the Spitzer Fellowship Program, under award 011 808-001.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.