Institute of Astronomy

Weather on Brown Dwarfs: New Insights from Synoptic Spectrophotometry and Fluid Instability Models

SpeakerTalk DateTalk Series
Adam Burgasser (UC San Diego)30 November 2017Institute of Astronomy Colloquia

Abstract

The coolest stars and brown dwarfs exhibit chemical, spectral and variability signatures indicating the presence of photospheric condensate clouds, which in turn serve as tracers for rotational and atmospheric dynamics. However, the precise nature of these clouds - their vertical, azimuthal and temporal structure, and their composition - have remained a challenge to model and infer. In this talk, I provide a brief summary of the research to date on brown dwarf weather, then focus on two areas in which important insights have emerged. First, I show that synoptic spectrophotometry, now possible at high precision with ground-based telescopes, demonstrates that small-grain particles at high altitudes may be the primary drivers for observed variability. Second, new atmosphere models integrating fluid instabilities are now able to reproduce many spectral signatures attributed to clouds without the need for cloud opacity. I attempt to synthesize these seemingly contrary perspectives and propose ways to further test what roles clouds do or do not play in shaping the spectra of cool brown dwarfs and hot exoplanets.

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