Tracing the variability or stability of exoplanet atmosphere escape, using ground-based low- and high-resolution spectroscopic observations of ultra-hot Jupiters.

Atmospheric escape is thought to sculpt the exoplanet population, carving features such as the radius gap and the Neptune desert. Close-in planets are subjected to intense XUV/EUV irradiation that can drive hydrodynamic outflows, but whether this loss is steady or episodic, and how it responds to stellar activity, is losely constrained due to a lack of multi-epoch observations that require large amounts of telescope time. Ultra-hot Jupiters (UHJs) are natural laboratories for these questions: their thermally ionized, chemically simple atmospheres and large scale heights make escape signatures readily detectable from few or even individual observations of their atmospheres. The physics we learn there can inform smaller, more vulnerable Neptune-sized planets, where escape may matter more for demographics but is far harder to observe.

High resolution: kinematics and epoch-to-epoch variability

High-resolution cross-correlation spectroscopy resolves line velocities and combines thousands of metal lines into species-specific detections, with a clean separation of planetary, stellar, and telluric signals. We are conducting a uniform re-analysis of archival high-resolution transmission spectroscopy observations for 13 UHJs to test how stable or variable escape-related signatures are from one epoch to the next, by carefully accounting for external sources of variabilty such as stellar activity, observing conditions, and reduction pipeline choices. Because archival epoch coverage can be sparse, we are planning to extend the program with the TOU high-resolution spectrograph on UF's DEFT, which WILL provide temporal coverage no public high-resolition instrument or archive can match.

Low resolution: the helium triplet as a scalable escape tracer

The metastable helium triplet at 10830 Å is a leading ground-accessible tracer of escaping gas. Our GTC/EMIR observations (R ∼ 1000) of the hot Jupiter WASP-69b test whether excess helium absorption can be detected at modest resolution, extending the escape question to a cooler, complementary regime. A successful detection would show that efficient, lower-cost helium surveys are feasible for many more targets, giving the breadth needed for population-level constraints. Together, the two approaches link the detailed physics of individual outflows to the demographic questions that motivate this work.

The Impact of Stellar Flares on Exoplanet Atmospheres

My most recent published work at the University of Florida with Dr. Jason Dittmann focused on finding stellar flares in data from the Transiting Exoplanet Sattelite Survey (TESS) mission.

We searched the TESS light curves of all M dwarf stars within 15 parsecs and determined a split in their relative activity levels based on their flaring frequency. Stellar flares may have a significant impact on planetary atmospheres, especially for exoplanets orbiting near their host stars. The most prevalent hosts of rocky exoplanets are these M dwarfs, as their small sizes and relatively low luminosities result in deeper transit depths, allowing for easier detections of Earth-like planets in their closer-in habitable zones. However, these stars are more active than Sun-like stars, so we additionally analyzed flares on M dwarf planet hosts recently observed or those with scheduled follow-up observations of their planets’ atmospheres with JWST (Cycles 1–4). We find consistent flaring for these targets compared with our volume-limited, 15 pc sample and split them into the relative activity categories.

With this work, we place the flaring of these planet hosts within the context of the local M dwarf population. This characterization is useful for determining optimal targets for follow-up observations of planetary atmospheres. Beyond the implications of stellar activity on exoplanet atmosphere retention, the signals associated with these stellar phenomena can significantly impact observed spectra and therefore complicate the interpretation and characterization of these atmospheres.

Young Exoplanet Detection

In 2024, our team detected and characterized the nearest Earth-sized exoplanet orbiting a Sun-like star, HD 63433 d. This newly-discovered world is the third planet found in this system, and it closely orbits its stellar host with a period of about 4 days. Notably, the host star is a member of a 400 Myr stellar association, making this triple-planetary system over 10x younger than our own solar system! Our team is working to better understand the physical/atmospheric properties of this young world. The publication I co-lead with Dr. Melinda Soares-Furtado is listed in my Publications section.

See the NASA discovery alert for our planet here, and my interview on the study here!

Dipper Stars

My collaboration and I published the largest catalog of Dipper Stars to date which you can find in my Publications section.

Dipper stars are a classification of young stellar objects that exhibit dimming variability in their light curves, dropping in brightness by 10-50%, likely induced by occultations due to circumstellar disk material. This variability can be periodic, quasi-periodic, or aperiodic.

These variable sources were found in a visual survey of TESS light curves, where dipping-like variability was observed. We found a typical age among our dipper sources of <5 Myr, with the age distribution peaking at ~2 Myr, and a tail of the distribution extending to ages older than 20 Myr. In our paper we presented the detection and characterization of the largest collection of dipper stars to date: 293 dipper stars, including 234 new dipper candidates. These dipper stars were part of our larger sample which in total made up a catalog of 414 young stellar variables.