Exploring Correlations of High Altitude Aerosol Formation in Planetary Systems with Similar Parameters

Abstract

High altitude aerosols prevent our ability to probe exoplanet atmospheres, by muting or completely obscuring molecular and atomic features. Unfortunately, the vast majority of planets are obscured by high altitude aerosols, and currently there is no way to a priori determine which planets are likely to be unobscured. Isolating a few system parameters that have strong correlations to high altitude aerosol formation would be invaluable for further atmospheric studies and lead to optimal usage of the next generation of facilities like JWST, ARIEL, and the ground-based ELTs. Towards this end, we have identified a subset of planets that are ideal to test correlations between stellar metallicity or high-energy irradiation levels and cloud coverage in exoplanet atmospheres. The most current comparative studies looking for correlations between the atmospheric properties of gas giants and parameters such as their masses, radii, stellar irradiation levels, stellar metallicities, etc, have yielded no clear trends likely because they are fitting too many parameters simultaneously to very small numbers of planets. Our subsets of seven planets differ because they match in most parameters, coined ”The Similar Seven”. In essence, these planets provide a control sample to search for correlations amongst the few differing properties (stellar metallicity and high-energy irradiation). This thesis provides the reduction and analysis techniques found to be most effective to process and detrend ground-based multi-slit spectroscopic data, with specific focus on Magellan/IMACS data. Our routines were initially implemented for WASP-31b, which is not apart of our similar seven sample. In addition new spectra of WASP-25b, WASP-96b, and WASP-124b, three of the seven spectra in our sample, are provided here. This leaves HATS-29b and WASP-55b that still need spectral observations, given that spectra of WASP-6b and WASP-110b have already been published. With the available five spectra we find a tentative correlation with optical atomic features, a proxy for high-altitude aerosol levels, and host star metallicity. This tentative correlation was found after homogeneously rederiving the stellar, planetary, and orbital parameters of every system in the sample in order to reduce biases when comparing parameters of each system. Though the precision of some of the transmission spectra is not high enough to strongly support the tentative trend, if found to be true this trend has the potential to be foundational in theoretical and observational exoplanet atmospheric studies. As such, there is planned work to more precisely measure optical data and obtain observations in both longer and shorter wavelengths.