Cuentos de las Estrellas: Understanding the Properties and Impacts of Stellar Flares Across Time and Wavelength

Abstract

The era of new space and ground based telescopes is providing us with more detailed exoplanet observations and advancing the search for life beyond our own solar system. These observations are providing opportunities to both study the makeup of these extrasolar worlds and also search for signs of habitability. However, stellar variability remains a limiting factor for planet detection and characterization. We see stellar contamination present in almost all exoplanet observations, especially around active M-type stars. Although it is seen as a source of contamination for most observations, stellar activity provides us with key insights into the larger star-planet environment. In order to understand and model the detailed properties of exoplanets we must understand the host stellar environment. Specifically, the signals generated by stellar magnetic activity need to be properly characterized and understood in order to gain a clear picture of the astrobiological implications stellar activity has on extrasolar worlds. To address these challenges, I have focused my thesis work on developing tools and leading studies that help us gain a better understanding of the properties and impacts of stellar flares across time and wavelength regimes. By leveraging existing datasets such as Spitzer, Kepler, TESS, and Gaia I have studied how stellar activity impacts our search for life on other worlds beyond our solar system. In the first part of this thesis I generate new tools for the community to use to model and understand photometric stellar activity in detail. Specifically, I use Kepler data to study the morphology or shape of stellar flares. I derive a continuous and analytical model to describe the shape of flare events in photometric observations. I test the flare template on datasets of various cadences and wavelengths and find the model is versatile enough to fit flare events in all of the tested cases. Furthermore, this flare template has already been used by other teams to model flares in both Kepler and TESS data \citep{Barclay2023TheC}. In the second part of this dissertation I study the energetics of flare events at infrared wavelengths. Even though flare emission peaks at near-ultraviolet and blue optical wavelengths, they emit energy across the entire electromagnetic spectrum. Flares in the infrared are only just beginning to be studied in detail as JWST is revealing they are a source of contamination for exoplanet studies. We use archival Spitzer observations of flares to constrain flare temperatures and understand their implications on exoplanet atmospheres. I turn to the active planet hosting star, TRAPPIST-1, to study how flare temperatures vary at infrared observations and in turn affect the exoplanets in orbit around the star. I also compare our results to the latest JWST observations of TRAPPIST-1. The third part of this thesis looks to the future to understand what upcoming flagship missions like the Nancy Grace Roman Space Telescope will provide for flare science. The final part of this thesis work explores how flare energetics change as a function of stellar mass and how the results impact the exoplanets around those stars. The resulting code and models developed for this thesis will be made open source to serve as tools for the greater astronomy and astrobiology communities.