Detecting Small Signals: Near-Infrared Studies of Substellar Companions

Citation

Buzard, Camillus Francis (2022) Detecting Small Signals: Near-Infrared Studies of Substellar Companions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/kwkz-t588. https://resolver.caltech.edu/CaltechTHESIS:05192022-142030043

Abstract

As the number of known exoplanets, or planets in other solar systems, grows, we have become empowered to ask deeper and more specific questions about the possibilities presented by our universe. A group of giant gaseous planets called "hot Jupiters" spurred us to think in new ways about giant planet formation. The diversity of solar system architectures, exoplanet sizes, atmospheric composition and dynamics expands our perspective on the many possible outcomes resulting from the same primordial ingredients in different amounts and in different environments. To fully answer these questions, we need to look directly into exoplanet atmospheres. Infrared spectra can reveal atmospheres' molecular content and certain physical processes, such as winds and rotation effects. From spectoscopic measurements, we can test theories of planet formation, evolution, and habitability. Unfortunately, most current direct exoplanet characterization techniques are limited to certain populations, whether planets with specific orbital geometries or planets either very far from or very near their host stars. These well-established methods miss a key population of exoplanets, specifically those that are non-transiting and with orbital separations between roughly 0.15 and 5 AU. This group contains around 19% of the exoplanets known today (a percentage which will only increase in the coming extreme precision radial velocity era) and will almost certainly include the nearest potentially habitable world. This dissertation presents two projects. In the first, we work to further a direct exoplanet characterization approach that will be sensitive to these elusive planets by identifying and reducing an insidious source of structured noise - in the process, making it easier to directly detect planetary emission. With advancements promised by the simulation framework presented in this dissertation, our multi-epoch direct detection approach, in combination with planet-to-star contrast gains enabled by high-contrast imaging technology, will be uniquely capable of characterizing ever smaller, cooler, and more complex planetary atmospheres. In the second project, we apply the direct detection method to a particularly interesting substellar object, a brown dwarf in a very close (<2 hour) orbit around a white dwarf, in order to understand how gaseous atmospheres behave in exotic irradiation environments. Together, these projects demonstrate the capacity of multi-epoch spectroscopic observations to serve as a window into gaseous atmospheres and a pathway to potentially habitable worlds.

Thesis Files