Dissertations, Theses, and Capstone Projects

Date of Degree

9-2016

Document Type

Dissertation

Degree Name

Ph.D.

Program

Physics

Advisor

Emily L. Rice

Committee Members

Kelle L. Cruz

Jacqueline K. Faherty

Michael C. Cushing

Charles Liu

Emily L. Rice

Subject Categories

Other Astrophysics and Astronomy | Stars, Interstellar Medium and the Galaxy

Keywords

brown dwarfs, exoplanets, low mass stars, spectral energy distributions, fundamental parameters

Abstract

The physical and atmospheric properties of ultracool dwarfs are deeply entangled due to the degenerate effects of mass, age, metallicity, clouds and dust, activity, rotation, and possibly formation mechanism on their observed properties. Accurate fundamental parameters for a wide range of substellar objects are crucial to testing stellar and planetary formation theories. To determine these quantities, we construct flux-calibrated spectral energy distributions (SEDs) for 234 M, L, T, and Y dwarfs and calculate bolometric luminosity (Lbol), effective temperature (Teff), mass, surface gravity, radius, spectral indexes, synthetic photometry, and bolometric corrections (BCs) for each object. We use these results to derive Lbol, Teff, and BC polynomial relations across the entire very-low-mass star/brown dwarf/planetary mass regime. We define a subsample of objects with age constraints based on nearby young moving group membership, companionship with a young star, or spectral signatures of low surface gravity. With this subsample, we derive new age-sensitive diagnostics and characterize the reddening of young substellar atmospheres as a redistribution of flux from the near-infrared into the mid-infrared. These results enable accurate, precise, and efficient characterization of very-low-mass objects with limited observational data.

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