- Protoplanetary disk chemical evolution
~~Effect of accretion in a viscously-evolving protoplanetary disk~~(published 2020)- Pebble drift with sublimation only
- Pebble drift + full chemistry
- Tidally distorted rocky planets
~~Constraining the composition of USP planets in the~~(published 2020)*Kepler*sample- Shapes of tidally-distorted transits and detectability
- Analytic Roche theory for modified polytrope planets

- Iteratively compute the surface density that is consistent with RADMC temperature profile
- This is important because the temperature determines viscosity, which determines the surface density of the gas and, by extension, the dust, which again feeds back into the temperature
- Couple a chemistry solver to the interpolated physical properties of the gas and dust as they accrete

- Found that accretion can increase the abundances of some species (like hydrocarbons) by orders of magnitude in the inner disk!
- Cosmic ray chemistry also plays an important role, since cosmic-ray driven chemistry can produce intermediates that are then transported to the inner disk

- Applies to midplane only — how does vertical mixing affect these results?
- Gas and dust are well-coupled; can we relax that assumption?

- Smoothed particle hydrodynamics is too noisy, and is very complex in cylindrical coordinates
- Boundary conditions in two dimensions are
non-trivial when we don't know the final
solution
*a priori* - Solving benchmarking problems is much easier than solving even a simple alpha-disk

- Physical model from Birnstiel+2010:
- One-dimensional disk surface density evolution equation
- Analytic prescription for dust velocity as a function of gas velocity
- Solve chemistry globally instead of locally with small water reaction network

- Classic ssurface density evolution equation:
$ \frac{\partial \Sigma}{\partial t} = \frac{3}{R} \frac{\partial}{\partial R} \left[R^{1/2} \frac{\partial}{\partial R} \left(\nu \Sigma R^{1/2}\right)\right] $

- Dust surface density evolution equation:
$ \frac{\partial \Sigma_d}{\partial t} + \frac{1}{R} \frac{\partial}{\partial R} \left[R \left(F_\mathrm{diff} + F_\mathrm{adv}\right)\right] = 0 $

- The Lynden-Bell & Pringle equation assumes Keplerian gas, but the dust equation does not — slight inconsistency
- Static temperature power law, which is not realistic
- Could couple to RADMC
- Could solve with flux-limited diffusion (this is likely more efficient, but more approximation)
- Do we expect a large difference?

Using this model, could we explain certain
“outlier” comets, such as 2I/Borisov, which
have high CO-to-H_{2}O ratios?

- Need realistic temperature structure
- Also may need stellar evolution to move the snowline

- Used a relaxation method (originally proposed by Hachisu), modified to include a point-source star, to solve for planet properties in extreme gravitational fields
- Showed that KOI-1843.03 is likely iron-enhanced to have survived at its position near or at the Roche limit

- Given:
- An equation of state for the core and mantle
- Pressure at center and core-mantle boundary
- Scaled separation from the star and axis ratio

- Use an iterative relaxation method to find self-consistent solutions (to a specified tolerance) for the planet density at all mesh points
- Planet properties cannot be specified in advance!

- Using software I wrote, we have generated lots of planet shapes and their properties
- Want to take those shapes and determine what their transits look like, then correlate with properties
- Also want to explore the possibility of actually detecting distortion

- Machinery to raytrace transits is in place
- More recently, added higher-quality RNG for photon generation
- Outside software used: ISPC, TBB, Embree, OSPRay

- Can we constrain compositions from transit light curves?
- Or is the effect washed out by limb darkening of the host star?
- How do we correlate properties with transit shapes?

- Last summer: Invited speaker, PETSc users meeting
- Upcoming:
- Astrochemical Frontiers (virtual meeting, will submit abstract by May 18)
- Heidelberg summer school on planet formation in protoplanetary disks (application due by June 1, but will university travel be allowed by August?)

- End of summer 2020: First pebble drift paper
- End of fall 2020: Tidally-distorted transits paper
- End of spring 2021: Second pebble drift paper
- Graduation in 2021

- Institute for Disease Modeling
- Perimeter or Flatiron Institutes