To measure the stellar and orbital properties of the metal-poor RS CVn binary o Draconis ( o Dra ) , we directly detect the companion using interferometric observations obtained with the Michigan InfraRed Combiner at Georgia State University ’ s Center for High Angular Resolution Astronomy ( CHARA ) Array .
The H -band flux ratio between the primary and secondary stars is the highest confirmed flux ratio ( 370 \pm 40 ) observed with long-baseline optical interferometry .
These detections are combined with radial velocity data of both the primary and secondary stars , including new data obtained with the Tillinghast Reflector Echelle Spectrograph on the Tillinghast Reflector at the Fred Lawrence Whipple Observatory and the 2-m Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory .
We determine an orbit from which we find model-independent masses and ages of the components ( M _ { \mathrm { A } } = 1.35 \pm 0.05 M _ { \odot } , M _ { \mathrm { B } } = 0.99 \pm 0.02 M _ { \odot } , system age = 3.0 \mp 0.5 Gyr ) .
An average of a 23 -year light curve of o Dra from the Tennessee State University Automated Photometric Telescope folded over the orbital period newly reveals eclipses and the quasi-sinusoidal signature of ellipsoidal variations .
The modeled light curve for our system ’ s stellar and orbital parameters confirm these ellipsoidal variations due to the primary star partially filling its Roche lobe potential , suggesting most of the photometric variations are not due to stellar activity ( starspots ) .
Measuring gravity darkening from the average light curve gives a best-fit of \beta = 0.07 \pm 0.03 , a value consistent with conventional theory for convective envelope stars .
The primary star also exhibits an anomalously short rotation period , which , when taken with other system parameters , suggests the star likely engulfed a low-mass companion that had recently spun-up the star .