I am currently a PhD candidate at Steward Observatory at University of Arizona. I study exoplanet formation and evolution, particularly in binary star systems, through direct imaging and high-contrast imaging ground-based observations. I'm a part of the MagAO-X team, the extreme adaptive optics instrument on the Magellan Clay telescope in Chile. I have also worked with Keck/NIRC2 images, and with unresolved companions in stellar binaries in Gaia.
Image: Orion Nebula from JWST/NIRCam, source: PDRs4All

Direct Imaging of Exoplanets in Reflected Light with GMagAO-X

Direct imaging of exoplanets to date has been limited to planets that are self-luminous - they are young enough and hot enough to glow in infrared wavelengths. This limits direct imaging to young, hot, massive planets on wide separations from their host stars. To fully probe the range of exoplanetary systems out there, we need to move to being able to image planets in the light they reflect from their host star, like how we see the Moon in the sunlight it reflects. The GMagAO-X instrument is an extreme adaptive optics instrument being built for the Giant Magellan Telescope in Chile, and it will be capable of imaging hundreds of exoplanets in reflected light from the ground. To prepare for these challenging observations, we need fully understand GMaxAO-X's ability to characterize their atmospheres and how to interpret their spectra, as well as figure out how to design GMagAO-X to maximize information content. I am conducting an internship at NASA Ames working with Natasha Batalha to model exoplanet reflected light spectra with GMagAO-X.

Pup Search: The ExAO non-interacting
white dwarf-main sequence binary system survey

White dwarfs are the only probes of the composition of non-volatiles in exoplanetary material due to their strong gravity. "Pollution" in white dwarfs is useful for a lot of informative science probing exoplanet composition outside ~5 AU, material that survived the AGB phase. About 30-50% of single white dwarfs have shown metal lines in thier spectra. So called "Sirius Like Systems" -- non-interacting white dwarf-main sequence binaries -- are probes of planetary systems around one star in a wide binary system. I am PI of the Pup Search (named for the White Dwarf Sirius B, "the pup", the companion to Sirius A the "dog star") - exploiting the high contrast imaging power of MagAO-X and SCExAO to find new white dwarf-main sequence binaries and obtain spectra with VIS-X and HST. They're good dogs.


Proper Motion Anomaly (PMa) is a change in the velocity of a star in the plane of the sky between the Hipparcos astrometric satellite (1991) and the Gaia astrometric satellite (2016). A change in velocity is an acceleration, which Newtonian mechanics tells us is caused by a massive object, like in this case a hidden stellar or substellar companion. We are using proper motion anomaly to generate a target list for detecting new young substellar companions in Scorpius Centaurus Star Forming Region with MagAO-X.

HIP 67506 AC

In Pearce et al. 2022 we detected a promising candidate companion signal at ~2 lambda/D which was estimated may be near the stellar/substellar mass boundary. In April 2022 we confirmed the candidate signal with MagAO-X and determined it is a mid-M dwarf. In this paper we also demonstrate that the previously-identified wide stellar companion HIP 67506 B is actually a much further distant background star.

Binary Differential Imaging

Planets are much much fainter than stars. In order to image a planet directly, we must remove the influence of the starlight to reveal the faint source lying underneath. Binary Differential Imaging leverages the advantage of simultaneously imaging a science target and a star to use to build a model of the point spread function by imaging both stars in a binary in a single image, and using each star as the reference for the other. I reduced a binary differential imaging dataset of 17 binaries imaged in L-prime band with MagAO/Clio on the Magellan Telescope from 2014-2017 using principle component analysis to recontruct the starlight model.

Boyajian's Star's Wide Companion

Boyajian's Star (aka KIC 8462852, aka Tabby's Star) has made waves in both astrophysics and the popular imagination due to its enigmatic light curve from the Kepler space telescope that is not well explained yet by any physical (or alien) theory (hint: it's not aliens). I showed that it has an here-to-fore unconfirmed wide stellar companion currently ~880 AU away. The companion is not an explanation for the light curve (despite claims to the contrary) but it is another piece of the puzzle.

Orbit Fitting of Wide Stellar Binaries with Gaia

The Gaia astrometric satellite provides unprecedented accuracy of astrometry motion. I showed that the relative velocity between two stars in a wide binary, for which both stars are well resolved by Gaia and have high quality astrometric solutions, can be used to constrain the orbital elements of the binary orbit.
I produced an open source python package that automatically fits orbital elements for two Gaia EDR3 sources with just the source ID numbers and a mass estimate for each.

Orbital Motion of Wide Planetary-Mass Companions to Low-Mass Stars

Planetary mass companions are large mass planets (on the order of 15 Mjup) on wide orbits (100’s of AU) from their host stars. They exist in a parameter such that it is unclear if they represent the high end of planetary masses, the low end of brown dwarf masses, or if there is even is a dividing line in the substellar mass function at all. I measured precise milliarcsecond astrometry of the PMC GSC 6214-210 B in 10 years of Keck/NIRC2 images, and fit the motion for orbital elements using the Orbits for the Impatient rejection sampling algorithm.

Stuff I've made

Exoplanet Occurrence Rates Plot

Everyone knows the obligatory semi-major axs vs mass plot that every exoplanet scientist is required by law to show in every talk. We wondered how literature occurrence rates would look overlaid on this plot. So we made it.
The hard work of compiling the literature was done by Rachel Bowens-Rubin, I made the plot pretty.
If you use it please give credit!

Projecc: A silly little python package for dealing with orbits

Projecc is a little python package for projecting orbital elements onto the sky plane and vice versa.


Mini lit reviews I wrote up to explain something to myself.

Combining filter curves with spectra

I often get confused on definitions and how to correctly report the flux in a filter.

Why is 60 deg the average inclination on a uniform half-sphere?

I did the math.

Gaia RUWE as an indicator of multiplicity

The Gaia astrometric satellite assumes each point source is a single star to fit astrometry to its motion. So the presence of subsystems unresolved in Gaia will cause the motion to deviate from a single star, and cause error in the fit. The error is encapsulated in the Renormalized Unit Weight Error (RUWE) term. Thus, RUWE can be used as a signpost of the presence of unresolved multiple stars.
In this unpublished mini-lit review I summarize recent work on RUWE and what it can reveal about unresolved multiples in Gaia DR2 and EDR3.

Astro References

Handy to have.