Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Aerospace, Physics, and Space Sciences

First Advisor

Eric S. Perlman

Second Advisor

Saida M. Caballero-Nieves

Third Advisor

Jean Carlos Perez

Fourth Advisor

Isaac Silver


The O’Connell effect – the presence of unequal maxima in eclipsing binaries – remains an unsolved riddle in the study of close binary systems. The Kepler space telescope produced high precision photometry of nearly 3,000 eclipsing binary systems, providing a unique opportunity to study the O’Connell effect in a large sample and in greater detail than in previous studies. I have characterized the observational properties – including temperature, luminosity, and eclipse depth – of a set of 212 systems (7.3% of Kepler eclipsing binaries) that display a maxima flux difference of at least 1%, representing the largest sample of O’Connell effect systems yet studied. I explored how these characteristics correlate with each other to help understand the O’Connell effect’s underlying causes. In studying these systems, I found that ∼30% of my sample belonged to four system classes with peculiar light curve features aside from the O’Connell effect: systems with temporal variation, systems with asymmetric minima, systems with a concave-up region, and a white dwarf. I studied the characteristics and correlations of the first three of these system classes to better understand how they differed from other O’Connell effect systems. Finally, I observed ten systems in my sample as a follow-up to Kepler’s

observations. I found that the O’Connell effect size’s correlations with period and temperature are inconsistent with Kouzuma’s (2019) starspot study. Up to 20% of systems display the parabolic eclipse timing variation signal expected for binaries undergoing mass transfer. Most systems displaying the O’Connell effect have the brighter maximum following the primary eclipse, suggesting a fundamental link between which of the maxima is brighter and the O’Connell effect’s physical causes. The systems displaying an asymmetric minimum are split into two fundamentally different subsets: temporally stable systems and temporally varying systems. Chromospheric activity largely explains the features observed in the peculiar system classes, aside from the temporally stable asymmetric minima systems. Most importantly, I found that the O’Connell effect occurs exclusively in systems where the components are close enough to significantly affect each other, suggesting that the interaction between the components may ultimately be responsible for causing the O’Connell effect.