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The origin of the long secondary periods (LSPs) in red variables remains amystery up to now, although there exist many models. The light curves of someLSPs stars mimic an eclipsing binary with a pulsating red giant component. Totest this hypothesis, the observational data of two LSP variable red giants,77.7795.29 and 77.8031.42, discovered by the MACHO project from the LMC, arecollected and analyzed. The probable eclipsing features of the light curves aresimulated by the Wilson-Devinney (W-D) method. The simulation yields a contactand a semidetached geometry for the two systems, respectively. In addition, thepulsation constant of the main pulsating component in each binary system isderived. By combining the results of the binary model and the pulsationcomponent, we investigate the feasibility of the pulsating binary model. It isfound that the radial velocity curve expected from the binary model has a muchlarger amplitude than the observed one and a period double the observed one.Furthermore, the masses of the components based on the density derived from thebinary orbit solution are too low to be compatible with both the evolutionarystage and the high luminosity. Although the pulsation mode identified by thepulsation constant which is dependent on the density from the binary-model isconsistent with the first or second overtone radial pulsation, we conclude thatthe pulsating binary model is a defective model for the LSP.

Testing a pulsating binary model for long secondary periods in red variables