Wavelength microns

114 J. Najita: The evolution of gas in disks

1.0 —i—i—nm—i—i—i—i—i—i—n~~n—i—r-

Wavelength (microns)

Wavelength (microns)

Figure 4. Spectrum of the transitional T Tauri star TW Hya in the 4.6 ¡m region (histogram), as shown in Figure 2, but here focusing on the structure in the continuum. The strong emission lines that extend above the plotted region are the bright CO fundamental emission lines seen in Figure 2. For comparison, the predicted stellar spectrum for TW Hya is also shown (lighter line). The model stellar spectrum fits many of the weaker features seen in the continuum. However, it predicts stronger stellar CO absorption in the low vibrational transitions (indicated by the lower vertical lines) than is seen in the measured spectrum. This suggests that the stellar photospheric spectrum is veiled by CO emission from warm disk gas.

would imply a higher temperature for the emitting gas that is consistent with the warm molecular gas that is inferred for this system from UV fluorescent molecular hydrogen lines (Herczeg et al. 2002).

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