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Session 40 - The Environment of Stars: From Protostars to the Main Sequence.
Display session, Tuesday, June 11
Great Hall,
We present sub-arcsecond imaging of the distribution of dust in the young binary system, T Tauri. Mid-infrared array and VLA aperture synthesis images resolve the 0.7'' binary in the wavelength ranges 7.8--12.5 \mum and 0.7--3.4 cm. At all wavelengths, the emission around each of the binary components is unresolved; no circumbinary disk is detected. In agreement with previous observations, the optically invisible ``infrared companion,'' T Tau S, dominates the emission at infrared wavelengths and in radio emission at \lambda = 1.3 and 3.4 cm. Surprisingly, the optical primary T Tau N radiates more strongly at \lambda = 7 mm.
For T Tau S, the spectral index in the range \lambda = 0.7--3.4 cm is \alpha = 1.2, consistent with free-free emission from an ionized wind, but too small to be attributed to thermal emission from circumstellar dust. For T Tau N, the emission at \lambda = 7 mm fits both an extrapolation from the submillimeter fluxes of the combined components with \alpha = 3.4 and from the radio fluxes for T Tau N with \alpha = 2.6. These results are consistent with predominantly thermal dust radiation as a source of the emission from T Tau N at \lambda = 7 mm; the change in slope at longer wavelengths may arise from an increasing free-free contribution at cm wavelengths. With the aid of a model of the spectral energy distribution, we interpret these results to indicate that most of the dust in the T Tau binary system lies within a disk around T Tau N. Dust associated with T Tau S, though less massive, is warmer and perhaps in a more active state of accretion onto the star.
