Hi, I'm Ian, a recent PhD from the Center for Astrophysics | Harvard &
Smithsonian. I focused on studying large exoplanets with large
telescopes and writing software to analyze them. I worked on all stages of the process, including extraction and reduction of the raw time series spectral
data, detrending of potential signals via different Gaussian Process (GP) and Principal Component Analysis (PCA) techniques, and the applications of a range of statistical Bayesian inference frameworks including Markov chain Monte Carlo (MCMC) and nested
sampling to study the atmospheres of these other worlds.
As a tutor coordinator, I was looking for an efficient way to match tutor-mentors with students. This turned into a fun weekend project turning the raw data from the awesome scheduling tool WhenIsGood into a colorful matching matrix showing the common overlap in different people's schedules.
WhenIsGood
An example of the site seen on the user's end. Just click and drag over your availability and submit when
you are done. The unix timestamps for the entries from each user is stored at the bottom of the results page HTML within
a javascript tag. I extract this data in the next step to create the following visualization.
Matching Matrix
This is the resulting matching matrix seen on the tutor coordinator's end. The data is automatically
downloaded, extracting, and post-processed to display the intersections between available dates/times for
all tutor-mentor / student combinations. A handy tooltip also displays the overlapping
times for a given tutor-mentor / student pair, which is automatically copied to the clipboard at the click of a
mouse.
Data wrangling/visualization of publicly available exoplanet data, with Julia and Pluto.jl.
Exoplanet locator
A groovy exoplanet sky chart created with data queried from the exoplanet archive, bright star locations from the Hipparcos, Yale Bright Star, Gliese (HYG) database, and asterisms from the Stellarium public repo.
System parameters calculator
Self-consistent computations of exoplanet parameters from stellar and orbital observations. Useful for
estimating the potential observability of an exoplanet's atmopshere.
Integrated orbit of a hypothetical three-body star-planet-moon system via s=2 Adams-Moulton method. This is motivated by the first potential discovery of an exomoon made not too long ago.
Population dynamics
The same integration method applied to the Lotka–Volterra system of differential equations describing population growth.
Orbital dynamics code written in Fortran, visualized in Python.
Artificial energy loss
Particle stream trajectory in a binary Roche Potential with artificial energy loss every time step to mimic the energy that is lost to shocks and other collisions in real fluid interactions. This was done by having the test particle lose energy while maintaining its angular momentum. I also added a little kick in the z component of the particle's initial velocity to make it a little more fun to watch.
WASP-12/b system
Top-down view of the same code applied to WASP-12/b (to scale). I waited until a full orbit to turn on the artificial energy loss to mimic one full lap of the accretion stream before colliding with itself. The corners due to the Coriolis force are clearly seen and the orbit settles down into its circularization radius (in green), as predicted from angular momentum conservation.
Hydrodynamical simulations of planetary cannibalism made with FLASH.
WASP-12/b 2D
An analog to the toy-model from the particle trajectory code above. I replaced the massless test particle in that code with a fluid outflow boundary, following properties adopted from Lai et al. (2010). I then added an artificial ramp up in density at around the 5 day mark to effectively fast-forward the disk to a more evolved state.
WASP-12/b 3D
I adapted the hydro simulation to 3D to create the image above. This is an isodensity contour plot taken partway through the simulation. The location of L1 can be seen as the orange-yellow sphere towards the bottom left. These simulations were used to create virtual light curves to compare with observations from HST's Cosmic Origins Spectrograph.
We present a new ground-based visual transmission spectrum of the hot Jupiter WASP-43b, obtained as part of ACCESS. We collected four transits observed between 2015 and 2018, with a combined wavelength coverage between 5300 and 9000 Å and an average photometric precision of 708 ppm in 230 Å bins. We perform an atmospheric retrieval of our transmission spectrum combined with literature Hubble Space Telescope/WFC3 observations to search for the presence of clouds/hazes as well as Na, K, Hα, and H₂O planetary absorption and stellar spot contamination. We do not detect a statistically significant presence of Na I or K I alkali lines, or Hα in the atmosphere of WASP-43b. We find that the observed transmission spectrum can be best explained by a combination of heterogeneities on the photosphere of the host star and a clear planetary atmosphere with water.
We present a new ground-based visible transmission spectrum of the high-gravity, hot
Jupiter HAT-P-23b, obtained as part of the ACCESS project. We derive the spectrum from five transits
observed between 2016 and 2018, with combined wavelength coverage between 5200 Å - 9269 Å in 200 Å bins, and with a
median precision of 247 ppm per bin. HAT-P-23b's relatively high surface gravity (g ~ 30 m/s²), combined with
updated stellar and planetary parameters from Gaia DR2, gives a 5-scale-height signal of 384 ppm for a
hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the planet with the tentative
presence of TiO, after simultaneously modeling stellar contamination, using spots parameter constraints from
photometry. If confirmed, HAT-P-23b would be the first example of a high-gravity gas giant with a clear
atmosphere observed in transmission at optical/NIR wavelengths; therefore, we recommend expanding observations
to the UV and IR to confirm our results and further characterize this planet. This result demonstrates how combining
transmission spectroscopy of exoplanet atmospheres with long-term photometric monitoring of the host stars can help
disentangle the exoplanet and stellar activity signals.
We present a new ground-based visual transmission spectrum of the hot Jupiter WASP-43b, obtained as
part of ACCESS. We collected four transits observed between 2015 and 2018, with a combined wavelength coverage
between 5300 and 9000 Å and an average photometric precision of 708 ppm in 230 Å bins. We perform an atmospheric
retrieval of our transmission spectrum combined with literature Hubble Space Telescope/WFC3 observations to search
for the presence of clouds/hazes as well as Na, K, Hα, and H₂O planetary absorption and stellar spot contamination.
We do not detect a statistically significant presence of Na I or K I alkali lines, or Hα in the atmosphere of
WASP-43b. We find that the observed transmission spectrum can be best explained by a combination of
heterogeneities on the photosphere of the host star and a clear planetary atmosphere with water.
