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Title: Variability in ultra cool dwarfs
Author: Clarke, F.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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Chapter one provides a brief overview of the physics of ultra cool dwarfs, and discusses relevant observation to date. Of particular import is an understanding of their atmospheric physics. The cool temperatures (2500K) of their atmospheres are condusive to the formation of molecules, the occurrence of chemistry and the condensation of solid and liquid particulates. The latter of these processes, which can be regarded as the formation of clouds, is especially interesting and poorly constrained by current theory and observation. One method of probing the structure, scale and distribution of clouds is to observe and characterise the variability they induce. In this dissertation, I present the results of observations designed to detect and characterise the photometric and spectroscopic variability induced by inhomogeneous cloud formations on ultra cool dwarfs. Chapters two and three describe observations and modelling of the brown dwarf Kelu-1. I report the discovery of a 1.8 hour periodicity in the object's brightness and discuss models to explain it. Chapter three then describes observations designed to test these models, and the conclusions that can be drawn from them. Observations of four further ultra cool dwarfs are described in chapter 4, and I report the discovery of photometric variability in two of them. These three chapters together form the most sensitive study of variability in ultra cool dwarfs made to date. In chapter five I discuss the possibility of imaging extrasolar plants and brown dwarfs around nearby white dwarfs. If discovered, these objets would be the "coolest" ultra cool dwarf known. Chapter six contains conclusions, and a brief summary of potential future work in this field.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available