Small planets show a radius valley near 1.8 R⊕ splitting them into rocky super-Earths and volatile sub-Neptunes, but whether rocky planets can be born rocky, or are all stripped cores of planets that lost an envelope, is still unsettled. We test two planet formation scenarios, Sub-Neptune (no planet born rocky) and Sub-Neptune+Super-Earth (some are), as priors to analyze this question. We...
Using a novel crossmatch of GALAH DR4 stellar abundances with K2 and TESS planet detections, we apply the gradient boosted decision tree ensemble model XGBoost to investigate relative importances of specific chemical abundances and molar ratios in predicting small planet hosts. In contrast to previous studies, we find a consistently high feature importance for oxygen across models. Using a...
I aim to determine the inclination of the rotation axis of stars that host exoplanets and to use that information to find the true mass of their exoplanets. To detect exoplanets via the radial velocity method, one measures the minute redshifts and blueshifts in a star’s spectrum as a star’s planet causes orbital reflex motion towards and away from the observer. The strength of the radial...
Ultra-cool dwarfs are the smallest and coolest stars on the main sequence. While M dwarfs are generally known to harbour a large number of planets, including rocky, Earth-mass exoplanets, the occurrence rate and architectures of planetary systems around ultra-cool dwarfs remain poorly constrained. To date, the only well-characterized planetary system around an ultra-cool dwarf is the...
The spatial distribution of starspots on red dwarf stars remains an open question in stellar astrophysics. Understanding whether red dwarfs’ starspots are preferentially equatorial—akin to the Sun—or are preferentially polar can give us insight into how these generate their magnetic dynamos and help to better characterize the atmospheres of the planets that orbit them as atmospheric...
Stellar ages are a foundational component of astronomy research, but are notoriously difficult to measure for low mass main sequence stars. Fortunately, variability indicators such as rotation period, flaring rate, and amplitude of flux variability can provide some age constraints, but they evolve in nonlinear and non-monotonic ways. Furthermore, these indicators are typically characterized as...
Convective boundary mixing occurs at the boundaries between convection and radiation zones in stars, where the material in the convection zone crosses the convective boundary. This can change the location of the convective boundary and bring more hydrogen into the core of the star, which has many effects on its evolution, including an extended main sequence lifetime. We use 1D stellar...
Trans-Neptunian Objects (TNOs) are small, distant bodies beyond Neptune that provide important context on the formation and evolution of the outer Solar System. However, the faintest TNOs are difficult to detect because their weak signals can be easily confused with noise and subtraction artifacts. Manual identification of genuine TNOs is therefore a time-consuming process that can require...
Exceeding temperatures of up to 3,300K, WASP—189b's dayside hemisphere is a unique laboratory in which we can probe the extreme atmospheric conditions experienced by the population of ultra-hot Jupiter (UHJ) exoplanets. Using high-resolution observations from GHOST on Gemini South, we detect various metals within WASP—189b's atmosphere, alongside a first tentative detection of neutral...
We report the first detection of brightness variability in an extremely metal-poor brown dwarf. These objects are ancient, very low-mass members of the Milky Way that formed when the Galaxy contained far fewer heavy elements than it does today. Using the 10.4-m Gran Telescopio Canarias, we found that the nearest known extreme T subdwarf, WISEA,J181006.1$-$101000.5, changes its $J$-band...
Type IIn supernovae (SNe) are a subclass of Type II SNe characterized by narrow hydrogen emission lines produced by interactions between SN ejecta and surrounding circumstellar material (CSM). Some Type IIn SNe show these features only briefly, indicating less extended CSM and motivating their classification as Type IIn-like SNe. The origin of this CSM remains a major outstanding...
This research presents the first mid-infrared characterization of the Galactic Center (GC) Wolf-Rayet (WR) and Ofpe/WN9 star population using integral-field spectroscopy from the JWST Mid-Infrared Instrument MRS. Data consist of calibrated, three-dimensional FITS spectral cubes spanning λ∈[4.9, 27.9] μm at resolving power R∈[1330, 3750]. As an initial application, the spectrum of the Ofpe/WN9...
Young stellar associations provide an opportunity to investigate the recent star formation history of the Solar Neighborhood by identifying groups of stars that share similar ages and kinematic properties. In this work, I investigate two nearby young stellar associations, SCYA 75 (Ophiuchus Southeast) and SCYA 103 (Scorpius-Centaurus), to explore whether their stellar populations show evidence...
To date, ALMA has conducted thousands of protostellar disk observations, and studying this archive has revealed much about the nature of these dusty disks around infant stars. Including that many of even the youngest disks contain an indicator of planet formation: axisymmetric substructures. However, the high computational/observational requirements of current methods mean only a small portion...
Young Stellar Objects (YSOs) range from the beginning of star formation (protostars) up until the beginning of the main sequence (T Tauri stars). By looking at the inception of the formation process, we can gain insight into stellar evolution, star-forming regions and their structures, and the motion of stars and surrounding matter. Using the Orion star-forming complex as a primary testing...
