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Session 22 - YSOs' Variability.
Display session, Monday, January 15
North Banquet Hall, Convention Center
We investigate the photopolarimetric variability of a magnetic accretion disk model for pre-main sequence T Tauri stars. In these dynamical models, material from a magnetically truncated Keplerian disk is accreted along magnetic field lines onto the stellar surface at high latitudes, resulting in two diametrically opposite UV hot spots which are the proposed origins of the UV excesses in T-Tauri stars. As the star rotates, the observed UV excess varies, as will the polarization arising from intrinsic spot polarization and also the scattering of spot radiation in the circumstellar disk. We investigate the photopolarimetric variability in a simplified model in which the hot spots are parameterized by two small circles with surface temperatures greater than that of the underlying star. The photopolarimetric variability is then calculated, as a function of stellar rotation, using a Monte Carlo radiation transfer code that calculates the emergent flux and polarization arising from the star -- spot -- disk system. We find that the resulting photopolarimetric variations are consistent with the observed variability in T-Tauri stars and suggest that this spot model is the source of the polarimetric variability in T-Tauri stars.
