Date of Award
Physics and Astronomy
Robert E. Stencel
Gareth R. Eaton
astrophysical disk, eclipsing binary, epsilon Aurigae, interferometry, orbital solution: radial velocity, astrometry, photometry
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.
Kloppenborg, Brian Keith, "Interferometric, Astrometric, and Photometric studies of epsilon Aurigae: Seeing the disk around a distant star." (2012). Electronic Theses and Dissertations. 850.
Recieved from ProQuest
Brian Keith Kloppenborg
Astrophysics, Astronomy, Physics