Collaborative Research: Using Brown Dwarfs to Understand Exoplanetary Atmospheres: Spectral Inversions of an Analog Population

Cuny Hunter College, New York NY

Investigators

Abstract

Astronomers are beginning to directly image exoplanets and obtain spectroscopic data. One of the chief barriers in interpreting the data is a complete understanding of condensate clouds. Typically, the data from exoplanet atmospheres are not good enough (and the sample size is too small) for direct determination of cloud properties. The standard technique involves 'forward-modeling' of planetary atmospheres from first principles using a grid technique. This work will use isolated, young brown dwarfs as analogs for massive exoplanet atmospheres. The team will use spectral inversion techniques on data from this population to make direct interpretations of brown dwarf atmospheres. These brown dwarfs typically have properties very similar to imaged exoplanets: temperature, luminosity, age, color, spectral features. However, they lack an obscuring parent star. This makes the spectra greatly easier to collect and allows for a much larger sample size. The team will examine a set of 26 young (5-130 Myr) isolated brown dwarfs from the same stellar associations in which large exoplanets have been discovered and imaged. They will use the BREWSTER code, developed by one of the team collaborators, to conduct spectral inversions. These inversions, along with empirical spectral energy fits and forwarding modeling using the BT SETTL code, will be used to (1) derive and compare fundamental parameters, (2) assess the dependence of cloud dynamics on environment, color and spectral features of the source object, and (3) examine compositional variations among directly-imaged exoplanets and exoplanet analogs. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.