Fall Tutorial – Finalized

After putting a lot of thought into my fall tutorial the plan is all set (mostly) and the paper work is filled out and going down the line of approval. I decided to use HYPERION which is a radiative transfer program written by T. Robitaille. It’s really new. The paper introducing the program came out in 2011 and the actual code library was released just within the past few months. I think it will be good for a few reasons 1.) It appears to cull the best parts of former radiative transfer libraries and combine into one package 2.) It has a python wrapper which I, the user, use to make my models 3.) The documentation seems really thorough especially given how new it is.

Instead of just “playing in parameter space” I’m going to actually try to make a model of the circumstellar environment of RR Tau. HYPERION produces synthetic SEDs and images as its results so it might be something that could be useful in conjunction with the observational data. Still, the primary goal is to learn about radiative transfer and understand these environments is greater detail which I think HYPERION will be perfect for.

I spoke with Bernadette today about this and she was very helpful in getting me started with how to approach this project. One of things we talked about is how current SED models of Herbig Ae/Be stars have dips in the SEDs (I’ll find a plot of this to put here to make this clearer) and that has been used as an indication for gaps and holes in the disk. The problem with suppositions like this from SED models is that they are not unique solutions so there is an uncomfortable level of uncertainty. The reason for this is because SEDs are the result of blackbody modeling so the inputs are distance from the material and the density of the material. From the way Bernadette described it the models pick the temperature distribution, I’m unclear of the specifics but basically the lack of constraints prevents the models from being rigorous.

One of the interesting things about HYPERION in light of this is that many of the inputs for the models get into the composition of the material in the system. It will be interesting to see how the results I get compare to previous SEDs produced from models.

Another thing that Bernadette brought up is that for SEDs of disks my optical monitoring won’t be useful in constraining the model because disks fall in the IR region. So I’ll have to see what data is already available from places like ISO and Spitzer.

CLOUDY came up in our conversation as a possible code library to look into. I actually have worked with CLOUDY before when I was doing work on quasar absorption lines at UMass. I was using it to get metallicity values from column densities but Bernadette said that it’s good for understanding winds. That’s definitely something I’m interested in but I think for just the sake of time (and sanity) I’ll focus on HYPERION for now.

Also, I got many many many papers and authors to read. I’ll be starting up Literature Reviews again with a vengeance.

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