The Truncated Disk of CoKu Tau/4

• Published in: The Astrophysical journal 2005-03, Vol.621 (1), p.461-472
• Main Authors: D’Alessio, Paola, Hartmann, Lee, Calvet, Nuria, Franco-Hernández, Ramiro, Forrest, William J, Sargent, Ben, Furlan, Elise, Uchida, Keven, Green, Joel D, Watson, Dan M, Chen, Christine H, Kemper, F, Sloan, G. C, Najita, Joan
• Format: Article
• Language: English
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/427490

We present a model of a dusty disk with an inner hole that accounts for the Spitzer Space Telescope Infrared Spectrograph observations of the low-mass pre-main-sequence star CoKu Tau/4. We have modeled the mid-infrared spectrum (between 8 and 25 mu m) as arising from the inner wall of a disk. Our model disk has an evacuated inner zone of radius similar to 10 AU, with a dusty inner "wall" of half-height similar to 2 AU that is illuminated at normal incidence by the central star. The radiative equilibrium temperature decreases from the inner disk edge outward through the optically thick disk; this temperature gradient is responsible for the emission of the silicate bands at 10 and 20 mu m. The observed spectrum is consistent with being produced by Fe-Mg amorphous glassy olivine and/or pyroxene, with no evidence of a crystalline component. The mid-infrared spectrum of CoKu Tau/4 is reminiscent of that of the much older star TW Hya, where it has been suggested that the significant clearing of its inner disk is due to planet formation. However, no inner disk remains in CoKu Tau/4, consistent with the star being a weak-emission (nonaccreting) T Tauri star. The relative youth of CoKu Tau/4 ( similar to 1 Myr) may indicate much more rapid planet formation than typically assumed.