2024JAVSO..52...78B

Time dependence of orbital inclination is examined for twelve nominally isolated, detached eclipsing binaries having published light curves acquired over intervals of thousands of orbits or more. The stars presented here are: alpha CrB, V526 Sgr, QX Car, AR Cas, FT Ori, V346 Cen, AI Hya, AG Per, YZ Cas, ? Aur, MY Cyg, and RZ Cha. In uniform treatment based upon a common reference set of orbital and absolute properties for each binary, uniform processing of observational histories yields apparent nutation per orbit from iterative fitting based upon precise reference parameters of a complete solution from the literature. Analytic weighting of each light curve is based upon fidelity to (WD) modeling, including corresponding absolute and orbital cited reference parameters. Empirical time dependence of orbital inclination is consistent with theoretically predicted combination of (a) long term exponentially decreasing misalignment of constituent rotations, and (b) short term periodic variation of precession associated nutation of eccentric orbits. Relative empirical nutation rate for these isolated binaries is in the range of 10^-4 to 0^-6 o/orbit. Nearly synchronous circular orbit (nominally isolated) binaries (YZ Cas, beta Aur, MY Cyg, RZ Cha) exhibit minimal but non-vanishing inclination rates.