V471 Tauri: Examining Eclipse Timing Variations with two Independent Clocks

Eclipse timing variations (ETVs) in binary systems can result from a plethora of potential mechanisms, one of which is the interaction of an unseen third body causing a periodic wobble in the system's barycenter. ETVs in the V471 Tauri dK+WD binary system have historically been attributed to such a cause. Using

the orbital period of the system (∼12.5-hr) and the spin period (∼9.25-min) of the WD as two independent clocks, we show that a third body

interpretation of the ETVs cannot adequately explain the nature of this system. A wobbling barycenter would introduce variations of equal magnitude to both

the eclipse timing and the spin period O-C diagrams. We present O-C diagrams for both clocks using photometric data spanning several years, noting a

relatively flat line for the spin-period O-C. We then argue for alternative mechanisms causing ETVs, namely the Applegate effect.