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R.G. Samec, D.W. Banks, R.B. Hernandez, L.A. Bright (Bob Jones University), D.R. Faulkner (U. South Carolina-Lancaster), D.B. Williams (Indianapolis, IN)
V523 Cassiopeiae has figured prominently in studies of very short period K-type nondegenerate eclipsing binaries over the past 15 years. It has one of the shortest orbital periods among such binaries, P = 336.5 minutes. Roche-lobe contact light curve solutions do not allow mass ratios near that determined from its radial velocity curve (qsp=0.42). It is also known to have a changing orbital period. BBSAG as well as other observers have patrolled this system over the past decade or so, observing hundreds of eclipse timings. In this paper we reveal 50 times of low light found from an archival search of Harvard plate stacks (DBW) in the interval from 1901 to 1942. We also present Johnson UBV light curves taken with the Lowell 0.79m reflecting telescope on the nights of 1998 September 15 to 17 (DRF). Six precision mean epochs of minimum light: 2451071.6881(3), 2451071.8046(2), 2451072.7395(1), 2451072.8566(2), 2451073.7928(3) and 2451073.9081(1) were determined. Some 430 timings of minimum light were gathered for this period study, covering nearly 152,000 orbits. The O-C residual curve yields a sinusoidal variation with a amplitude of 0.040(8) days, and a period of 106(10) years, overlain upon a continuous period increase with a quadratic term of 1.1 X10-11 d/E2. Assuming that the periodic oscillation is due to a third star in the system, and the inclination from our orbital solution for the close pair is the same as the larger orbit, the third star is calculated to have 0.36 solar masses. This is similar to the masses of the stars that comprise the contact binary (0.88 solar masses). Thus, the entire system consists of a trio of late K and early M-type dwarfs, if this scenario is correct. A linear fit to recent timings yields the following ephemeris: J.D. Hel Min I = 2446708.7709(8) d + 0.23369222(7) X E. A simultaneous UBV synthetic light curve-radial velocity curve analysis is reported. Our small team of three undergraduate researchers performed most of the analyses and reductions. This research was partially supported by a grant from NASA administered by the American Astronomical Society.
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