Description
Stellar ages have consistently been one of the most difficult quantities to precisely measure in astronomy. Open star clusters are prime targets for checking age measurement techniques. We primarily focus this project on 12 Com in the cluster Coma Berenices. 12 Com is a spectroscopic binary system consisting of a G7 giant and A3 dwarf. Using radial velocities from various sources and interferometric measurements from PTI and CHARA, we have measured the size of the binary orbit in the sky. The orbital parameters of the system can then be used to obtain very precise values for the mass. The masses, 2.73 ± 0.10 M and 2.14 ± 0.04 M for the primary and secondary stars respectively play particularly important roles as we can use MIST evolutionary tracks to constrain the age of the binary and therefore the cluster. The color-magnitude diagram position of the binary constrains the giant, resulting in an age of 473 ± 40 Myr. Interferometry also lets us resolve the physical size of the giant to be 9.12 ± 0.02R. Pairing this with the masses obtained from the fits gives us an age of 455 ± 15 Myr from the evolutionary tracks. This implies that the giant is likely the most evolved star in the cluster, large enough to be in the red giant phase, but too small to have helium core burning, eliminating the possibility of existing in that phase. Age error bars quoted above are entirely statistical uncertainties, and do not include systematic uncertainties present from the evolutionary models. Getting the convective core overshooting wrong by just a little causes the time on the main sequence and overall shape of the evolutionary track to change. We expect that the increase in precision for the age measurements will provide insight into the internal physics governing the evolutionary modeling code.
