2008AJ....136.2158T

We present new V-band differential brightness measurements as well as new radial-velocity measurements of the detached, circular, 0.84 day period, double-lined eclipsing binary system, CV Boo. These data, along with other observations from the literature, are combined to derive improved absolute dimensions of the stars for the purpose of testing various aspects of theoretical modeling. Despite complications from intrinsic variability that we detect in the system, and despite the rapid rotation of the components, we are able to determine the absolute masses and radii to better than 1.3% and 2%, respectively. We obtain M_A= 1.032±0.013 M_☉ and R_A= 1.262±0.023 R_☉ for the hotter, larger, and more-massive primary (star A), and M_B= 0.968 ±0.012 M_☉ and R_B= 1.173±0.023 R_☉for the secondary. The estimated effective temperatures are 5760±150 K and 5670±150 K, respectively. The intrinsic variability with a period ∼1% shorter than the orbital period is interpreted as being due to modulation by spots on one or both components. This implies that the spotted star(s) must be rotating faster than the synchronous rate, which disagrees with predictions from current tidal evolution models according to which both stars should be synchronized. We also find that the radius of the secondary is larger than expected from stellar evolution calculations by ∼10%, a discrepancy also seen in other (mostly lower-mass and active) eclipsing binaries. We estimate the age of the system to be approximately 9 Gyr. Both components are near the end of their main-sequence phase, and the primary may have started the shell hydrogen-burning stage.