Date of Award

1-1-2012

Document Type

Dissertation

Degree Name

Ph.D.

Department

Physics and Astronomy

First Advisor

Robert E. Stencel

Second Advisor

Gareth R. Eaton

Keywords

astrophysical disk, eclipsing binary, epsilon Aurigae, interferometry, orbital solution: radial velocity, astrometry, photometry

Abstract

Epsilon (ε) Aurigae is a binary star system that has baffled astronomers for 170 years. In 1821 it was first noticed that the star system had dimmed by nearly 50%. After many decades of photometric monitoring, the 27.1 year period was finally established in 1903. A few years later, in 1912, Henry Norris Russell published the first analytic methods for binary star analysis. Later application of these formulae came to an interesting conclusion; the system was composed of two stars: the visible F-type supergiant, and an equally massive, but yet photometrically and spectroscopically invisible, companion.

Several theories were advanced to explain this low-light to high-mass conundrum, eventually settling on the notion that the companion object is obscured from view by a disk of opaque material. With this topic solved, the debate shifted the evolutionary state of the system. Two scenarios became dominant: the system is either relativity young, and composed of a massive, 15 Mo (solar mass), F-type supergiant and a nearly equally massive main sequence companion inside of the disk; or a much older and significantly less massive, 4 Mo, F-type post-asymptotic giant branch object with a more massive, 6 Mo, companion surrounded by a debris disk.

In this dissertation I disentangle the two evolutionary states by comparing the photometric behavior of the F-type star to known supergiant and post-asymptotic giant branch objects; and deriving a dynamical mass for the two components using astrometric, radial velocity, and interferometric data. Along with this, I provide the first interferometric images during the eclipse which prove the 50% dimming is indeed caused by an opaque disk.

The first chapter presents the reader with the status quo of ε Aurigae research and the topics I wish to address in this dissertation. Chapter two presents an analysis of nearly 30 years of photometry on the system, concluding the star periodically exhibits stable pulsation on 1/3 orbital timescales. The next two chapters are complementary in many ways. Chapter three presents the first interferometric images of ε Aurigae during eclipse and models the star and eclipsing body in unprecedented detail. Chapter four presents new combined astrometric and radial velocity orbital solutions using a myriad of historical data sources and modern analysis techniques. Lastly in Chapter five I conclude that the system is in the high-mass evolutionary state and provide estimates of the system component masses and distance.

Provenance

Recieved from ProQuest

Rights holder

Brian Keith Kloppenborg

File size

214 p.

File format

application/pdf

Language

en

Discipline

Astrophysics, Astronomy, Physics

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