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To measure the stellar and orbital properties of the metal-poor RS CVn binaryo Draconis (o Dra), we directly detect the companion using interferometricobservations obtained with the Michigan InfraRed Combiner at Georgia StateUniversity's Center for High Angular Resolution Astronomy (CHARA) Array. TheH-band flux ratio between the primary and secondary stars is the highestconfirmed flux ratio (370 +/- 40) observed with long-baseline opticalinterferometry. These detections are combined with radial velocity data of boththe primary and secondary stars, including new data obtained with theTillinghast Reflector Echelle Spectrograph on the Tillinghast Reflector at theFred Lawrence Whipple Observatory and the 2-m Tennessee State UniversityAutomated Spectroscopic Telescope at Fairborn Observatory. We determine anorbit from which we find model-independent masses and ages of the components(M_A = 1.35 +\- 0.05 M_Sun, M_B = 0.99 +\- 0.02 M_Sun, system age = 3.0 -\+ 0.5Gyr). An average of a 23-year light curve of o Dra from the Tennessee StateUniversity Automated Photometric Telescope folded over the orbital period newlyreveals eclipses and the quasi-sinusoidal signature of ellipsoidal variations.The modeled light curve for our system's stellar and orbital parameters confirmthese ellipsoidal variations due to the primary star partially filling itsRoche lobe potential, suggesting most of the photometric variations are not dueto stellar activity (starspots). Measuring gravity darkening from the averagelight curve gives a best-fit of beta = 0.07 +\- 0.03, a value consistent withconventional theory for convective envelope stars. The primary star alsoexhibits an anomalously short rotation period, which, when taken with othersystem parameters, suggests the star likely engulfed a low-mass companion thathad recently spun-up the star.

Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries: II. omicron Draconis, a Candidate for Recent Low-Mass Companion Ingestion