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C.H.S. Lacy (U. Arkansas), B.E. Helt (Niels Bohr Inst.), L.P.R. Vaz (UFMG)
V907 Sco is discovered to be unique among all known eclipsing binary stars because its eclipses have turned on and off twice within modern history. The system is at least a triple star consisting of a (sometimes) eclipsing binary star (B9.5V) with an orbital period of 3.78 days, and a faint, distant companion with an orbital period of 99.3 days. Radial velocity measurements allow the masses to be estimated. Because the orbital planes of the eclipsing binary and its triple companion are not co-planar, the orbital plane of the eclipsing binary shows nodal regression with a period of 68 years. For about 1/3 of this time, the close binary is eclipsing. The earliest observations of the system in the year 1899 show eclipses; the eclipses stopped about 1918, started again about 1963, and stopped again in about 1986. We predict that the eclipses should start occurring once again in the year 2030.
The author(s) of this abstract have provided an email address for comments about the abstract: clacy@comp.uark.edu