Age Determination for the Open Cluster NGC 6939 from the Eclipsing Binary Member V12

Measuring precise ages in astronomy is a very difficult task, but star clusters often provide the best opportunities to make age determinations. A star cluster generally contains stars of the same age, and among these stars eclipsing binary systems can lead to high-precision measurements of the masses and radii of the two orbiting stars.  If an eclipsing binary contains a star that is rapidly changing in size because it is running out of hydrogen fuel at its center, then these measurements can lead to a precise age. We performed a study of the eclipsing binary star V12 in the open star cluster NGC 6939 by monitoring its brightness during eclipses with the Mount Laguna Observatory 1 meter telescope and the radial velocities of the stars using the 9-meter Hobby-Eberly Telescope. We have analyzed photometry and radial velocity data for binary star V12 to derive precise masses and radii, and will present a new determination of the age of the cluster