Testing Stellar Models with an Improved Physical Orbit for 12 Bootis

We report on a significantly improved determination of the physical orbit ofthe double-lined spectroscopic binary system 12 Boo. We have a 12 Boointerferometry dataset spanning six years with the Palomar TestbedInterferometer, a smaller amount of data from the Navy Prototype OpticalInterferometer, and a radial velocity dataset spanning 14 years from theHarvard-Smithsonian Center for Astrophysics. We have updated the 12 Boophysical orbit model with our expanded interferometric and radial velocitydatasets. The revised orbit is in good agreement with previous results, and thephysical parameters implied by a combined fit to our visibility and radialvelocity data result in precise component masses and luminosities. Inparticular, the orbital parallax of the system is determined to be 27.74 $\pm$0.15 mas, and masses of the two components are determined to be 1.4160 $\pm$0.0049 M$_{\sun}$ and 1.3740 $\pm$ 0.0045 M$_{\sun}$, respectively. Based ontheoretical models we can estimate a system age of approximately 3.2 Gyr.Comparisons with stellar models suggest that the 12 Boo primary may be justentering the Hertzsprung gap, but that conclusion is highly dependent ondetails of the models. Such a dynamic evolutionary state makes the 12 Boosystem a unique and important test for stellar models.Comment: 34 pages, 10 figures; accepted by Astrophysical Journal; Data tables to appear in ApJ on-line version; corrected typo in abstrac