[Previous] | [Session 6] | [Next]
B.J. McNamara, T.E. Harrison, R.T. Zavala, E. Galvan, J. Galvan, T. Jarvis, G. Killgore, O.R. Mireles, D. Olivares, B.A. Rodriquez, A.L. Silva, Andrea Silva, E. Silva-Velarde (New Mexico State University)
Over 100 years of eclipse timings for the Algol binary WW Cygni show that this system has a 56 year cyclic variation in its orbital period, with an amplitude of ~ 0.02 days. We consider and reject the hypotheses of mass transfer, apsidal motion, and the gravitational influence of an unseen third body as the cause of these variations. The most likely explanantion, proposed by Applegate, is that magnetic cycles in the convective secondary star produce changes in the gravitational quadrupole moment of this component. These quasi-periodic quadrupole moment variations are manifested in the observed cyclic period changes. Following Applegate's predictions, we also attempt to probe the internal rotational structure of the convective secondary using eclipsetimings and multi-color photometry. This work was supported by the NSF.