The last decade has seen the advent of direct characterisation of the atmospheres of giant exoplanets via high contrast imaging and spectroscopy. However, interpreting these data can be problematic due to their sparse nature and poor signal to noise resulting from the challenging nature of the observations. Unhindered by bright host stars but sharing the same temperatures, free floating brown dwarfs and planetary mass objects have become crucial laboratories for understanding the complex physics and chemistry of these atmospheres. Dr Burningham has developed software (named "Brewster") for studying these atmospheres using spectral inversion (also known as retrieval analysis) with a particular emphasis on understanding their clouds, chemistry and thermal structure. Dr Burningham is leading the retrieval analysis for two approved Cycle 1 JWST programmes using Brewster - both of these provide opportunities for PhD projects.
Spectrophotometry of brown dwarf pulsars: This project will use JWST time series data to disentangle the impacts of weather (clouds) and aurorae on the spectra of brown dwarfs that are known to have powerful radio aurorae and near-infrared variability. This will require developing a strategy for analysing the incredible quality time series data that will be supplied by our JWST programme during Cycle 1 within the Brewster framework. It will also involve extending the Brewster retrieval model to include the effects of aurorae and derive information from the model parameters that can be used to constrain how the aurorae interact with the brown dwarf atmosphere.
The coldest observed extrasolar atmospheres: This project will focus on using Brewster to understand the conditions in the atmospheres of extremely cool Y dwarfs that will be observed by JWST in Cycle 1. Y dwarfs span the temperature range from 250K up to around 500K, and represent the coldest directly observed atmospheres beyond the solar system. Their masses overlap with the planetary regime, and the population may include examples of ejected planets. The coldest examples are expected to show evidence of water clouds in their spectra, whist warmer examples may show exotic clouds formed from halides or alkali sulphides. Due to their cool temperatures, Y dwarfs are extremely faint at near-infrared wavelengths, and are essentially invisible at optical wavelengths. Since their discovery in 2011 it has only been possible to obtain relatively poor quality near-infrared spectra using Hubble. JWST will provide the first high quality spectroscopy across the wavelengths where they emit most of their light, which will revolutionise our understanding of these objects. By using Brewster to analyse JWST spectroscopy of these objects this project will provide the insights to their clouds, chemistry and thermal structure.