Date of Award

2006

Document Type

Restricted Thesis

Terms of Use

© 2006 Andrew Skemer. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Physics & Astronomy Department

First Advisor

Eric L.N. Jensen

Abstract

This paper summarizes current knowledge of circumstellar debris disks and presents methods of modeling optically thin disks. The techniques of Bayesian statistics and marginal probabilities are applied to the disk modeling problem so that I can construct probability distributions for individual disk parameters. I apply these methods and interpret the results for three stars: HD 105, HD 107146, and HD 115043.

In the introduction, I give background information on circumstellar disks, and their possible connection with dust in the Solar System. I describe the general technique of modeling infrared excesses, and present the goals of this paper. Because the stars I study are unresolved in the wavelength range of dust emission, the flux contributions of a star and its disk must be separated before I can model the disk parameters. To do that, I model the star's photosphere, and subtract its contribution from the data.

In the body of the paper, I describe the data and the modeling procedures for the photosphere and the circumstellar disk. I present the methods of Bayesian statistics and marginal probabilities as they apply to this paper, and I use the techniques to analyze the three star sample. The methods of Bayesian/ marginal statistics reveal probability distributions of seven disk modeling parameters for each star, and in many cases, place constraints on important parameters such as inner radius and disk mass. HD 107146 has a resolved disk in scattered light, and the results of my marginal distributions are compared to the resolved data. I also examine the results of HD 107146 with and without millimeter data to demonstrate the usefulness of long-wavelength observations for constraining the disk's inner radius and dust absorption/emission parameters. I conclude the paper with a list of future steps—both short-term and long-term.

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