Research

Figure 9 from Schmidt et al. 2023.

Gaia + TESS = Transiting Brown Dwarfs & Very Low-mass Stars

Gaia's third data release presented tens of thousands of single-lined spectroscopic binary systems' orbital parameters, but it is only sensitive to things much more massive than exoplanets. This includes brown dwarfs, which aren't massive enough for their cores to fuse hydrogen, and low-mass stars that are (but are still quite faint). We can use these orbit fits to infer the minimum mass of the much fainter secondary. This is nice, but not as informative as having an upper limit as well, which we need an inclination to get. Combining Gaia's catalog with transits (which get you the inclination) from the Transiting Exoplanet Survey Satellite (TESS) mission results in masses and radii for hundreds of transiting low-mass stars or brown dwarfs!

I presented a poster on this at Exoplanets V in June 2024, so you might have seen it there!

You can read more about this paper here! (Verification of Gaia Data Release 3 Single-lined Spectroscopic Binary Solutions With Three Transiting Low-mass Secondaries)

Figure 2 From Schmidt, Schlaufman, and Hamer 2024.

The Ages & Evolution of Resonant and Ultra-short-period Small Planets in Kepler

Stars in our galaxy form close to the mid-plane of the disk and experience random kicks over billions of years. Because of this, the velocity dispersion of a sample of stars (i.e. how much their 3D velocities vary as a group) increases as the sample gets older. When we measure this velocity dispersion for exoplanet systems, we can tell which exoplanet populations are older or younger than others. If you then calibrate the relationship between age and velocity dispersion in a region of our galaxy, you can also obtain age offsets between those exoplanet populations. I used this methodology to show that ultra-short-period planets, small planets that orbit their host stars in under a day, have taken billions of years to tidally migrate to their observed locations.

If you were at Extreme Solar Systems V in March 2024 or Exoplanets V in June 2024, you have heard me speak about this!

You can read more about this paper here! (Resonant and Ultra-short-period Planet Systems Are at Opposite Ends of the Exoplanet Age Distribution)

Figure 4 from Schmidt et al. 2025.

The Nature of K2-18 b from its JWST NIRISS & NIRSpec Transmission Spectrum

K2-18 b is a sub-neptune, a class of exoplanets that are massive enough to have accreted a sizeable amount of volatiles (molecules that vaporize at low temperatures) but not massive enough to clearly have a gas giant-like structure (i.e. hydrogen-dominated and no surface). There are a variety of theoretical models for what structures are plausible for these kinds of planets, but there are many degeneracies that make it difficult to distinguish one from another. Previous observations of K2-18 b using the James Webb Space Telescope's NIRISS and NIRSpec instruments were used to claim that it might have signs of harboring a liquid water surface ocean, but when my collaboration reanalyzed those data in the context of updated atmosphere and interior modeling, we did not find evidence in support of this claim.

I presented a poster about this work at ExoClimes VII in July 2025, so you might have seen it there!

You can read more about this paper here! (A Comprehensive Reanalysis of K2-18 b's JWST NIRISS+NIRSpec Transmission Spectrum)

Figure 2 From Schmidt & Schlaufman 2025.

The Origins of Hot Jupiters via a Kinematic Age Study of their Orbital Period Distribution

In a similar fashion to my paper on the Kepler field, applying my age-velocity dispersion relation methodology to the solar neighborhood allows us to probe the formation of hot Jupiters, giant exoplanets that orbit their host stars in under 10 days. Splitting the hot Jupiter population into three subpopulations based on their debiased orbital period distribution, we find that most hot Jupiters migrated inward to their observed separations over a billion years after they initially formed.

If you were at Know Thy Star, Know Thy Planet II in February 2025, you have heard me speak about this!

I recently submitted this paper and will be talking about it at NOIRLab's The Solar System In Context in September 2025 and the 51 Pegasi b 30th Anniversary Conference in October 2025! (Most Hot Jupiters Were Cool Giant Planets for More Than 1 Gyr)

Figure from Schmidt, Thorngren, & Schlaufman 2025.

Shallow Heating in the Hot Jupiter Population via Delayed Interior Cooling

Hot Jupiters have larger radii than they are predicted to have based on theoretical models of cool giant planet structure. This has led to much debate about what kinds of physical processes are heating their interiors and thereby inflating their radii. Some processes take place deep in the interior and are able to reinflate hot Jupiters as their host stars expand and brighten as they age. Others occur at much shallower depths and are only able to delay the rate at which a planet initially shrinks after it forms. Investigating the hot Jupiter population as a whole using a homogeneous set of stellar parameters and state-of-the-art giant planet interior thermal evolution models, we find that shallow heating is responsible for most of this observed radius inflation.

I presented a poster about this work at Know Thy Star, Know Thy Planet II in February 2025, so you might have seen it there!

I am going to be submitting this paper imminently! A link will appear once it is accepted. (Shallow Heating is the Dominant Source of Hot Jupiter Radius Inflation)

Figure 14 From Wang et al. 2025.

A Tidal Evolution Model for Exoplanet Systems

Using the Leconte et al. 2010 coupled ODEs for an exoplanet system's tidal evolution in conjunction with Amard et al. 2019 stellar tracks with rotation, I have created a forward model for the tidal evolution and fates of exoplanet systems, I previously used this in my second paper to investigate USP planet formation, but here I used it to investigate the fate of HAT-P-67 b under different assumptions for tidal dissipation efficiency.

You can read more about my contribution in this paper here! (A Revised Density Estimate for the Largest Known Exoplanet, HAT-P-67 b)

Figure 21 From Mukherjee et al. 2025b.

JWST Atmosphere Retreivals with POSEIDON

I use the publicly-available POSEIDON exoplanet atmosphere retrieval code to perform atmosphere retrievals for the JWST Grand Tour Spectroscopic Survey (GO 5924). In the case of WASP-94 Ab, my retrievals on the spherical NIRISS SOSS transmission spectrum showed that not considering limb asymmetries during the retrieval analysis could significantly bias atmospheric metallicity measurements.

You can read more about my contribution in this paper here! (Cloudy mornings and clear evenings on a giant extrasolar world)

JWST Data Reduction with the FIREFLy Pipeline

In addition to my retrieval work for the JWST Grand Tour program, I'm also responsible for producing data reductions for several of our targets, including HAT-P-1 b in NIRSpec G395H, KELT-7 b in NIRISS SOSS, WASP-76 b in NIRISS SOSS, and WASP-12 b in NIRSpec PRISM. These papers are still forthcoming and/or the data has not yet been taken, so I can't show any figures from them yet.

My Research