Modeling UV emission from accretion

 

I created an updated version of the Calvet & Gullbring (1998) accretion shock models to reproduce the observed UV excess for the largest sample of Classical T Tauri Stars with multiple HST STIS observations. I found significant amounts of variability on timescales of days to weeks. One of the targets displayed evidence of a dusty accretion column connecting the inner disk to the stellar surface, which is contrary to the canonical picture of a dust-free inner gas disk. One of the other objects showed changes in the UV excess as large as an order of magnitude over timescales of about a week.

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Simulations of accretion onto young stars

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I constructed a 1D time dependent simulation that traces along the magnetic field from the footprint in the disk to the shock at the star. This simulation found that small shocks can form near the disk and propagate towards the star if density perturbations are present in the disk. I also connected these simulations with the accretion shock models above to generate synthetic light curves to make predictions about the effect of disk/star parameters on the observed light curves. 

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D'Alessio Irradiated Accretion Disk (DIAD)

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Using the radiative transfer/disk structure code, DIAD, I can create model spectral energy distributions of transitional and pre-transitional protoplanetary disks. Below is an example of one of the models. The black line is the model, the red lines are spectra and the green points are photometry. The different components of the disk that the model simulates are shown as segmented lines.

 

These models allow us to obtain physical parameters associated with these systems such as dust grain size, settling, viscosity, and the inner and outer radii of the disk.