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Session 41 - T Tauri Stars & Protostellar Regions.
Display session, Wednesday, June 11
South Main Hall,
We report the results of Monte Carlo simulations of photopolarimetric variability in T Tauri stars (TTS). In particular, we have created a time-variable, multi-wavelength model of a rotating star with hot spots, surrounded by a circumstellar disk.
This study is motivated by recent theoretical work (e.g. Shu et al. 1994) which predicts that hot spots on stellar surfaces will arise as the result of magnetically channeled accretion of disk material. According to the theory, the stellar magnetic field threads the disk, truncating it within a certain inner radius and carrying disk material along field lines to the stellar surface. The impact of these accretion streams on the surface generates hot spots, which produce periodic photometric variability such as is commonly observed among TTS (e.g. Bouvier et al. 1993).
Our modeling shows that the presence of such spots will also produce periodic polarimetric variability, and that this variability depends not only on spot properties (size, position, etc.) but on inner disk properties as well. Specifically, we find that the amplitude, morphology, and wavelength dependence of the polarimetric variability are highly sensitive to the inner radius at which the circumstellar disk is truncated.
This study demonstrates the potential usefulness of polarimetry as a diagnostic of inner disk morphology in TTS. The modeling presented here provides a means of interpreting such polarimetric observations within the context of a theory which has become central to our understanding of early stellar evolution.
Program listing for Wednesday