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R.G. Samec, M.L. Stoddard (Bob Jones University), D.R. Faulkner (University of South Carolina-Lancaster)
TY UMa [SVS 366, RA(2000) = 12h 9m 2.656s, DEC(2000) = 56deg 01' 53.54"] is a W UMa binary which has been modeled in both near and shallow contact configurations (Broglia and Conconi 1983). Our recent light curves show similar attributes. However, the orbital period reveals a major and continuous change which may point to an accelerating period change over the past 36 years and possibly 66 years. Alternately, there may be a third body producing a light time amplitude of 0.124(5) days and an orbital period of 103(4) years. The present UBV observations were taken with the Lowell 0.79m reflecting telescope on April 9-11 1999. Four mean epochs of minimum light were determined from the observations made during two primary and two secondary eclipses by MLS using the bisection of chords technique. These are 2451278.8626 (2), 2451279.74951 (4), 2451279.9267 (1), 2451280.8124 (7). Recent timings yield,tangent to the curve, the following linear ephemeris: J.D. Hel Min I = 2450193.5726(46) d + 0. 35454228 (22) X E. Simultaneous, Wilson Code UBV light curve synthesis models are presented. MLS performed much of the analysis in her undergraduate research project. RGS and DRF were visiting Astronomers at Lowell Observatory, Flagstaff, Arizona This research was partially supported by a grant from NASA administered by the American Astronomical Society. References: Broglia, P., Conconi, P. 1981, A&AP 51, 97b