Kepler Binary Stars in NGC 6819 Open Cluster: KIC 5113146 and KIC
  5111815
  In this study, investigation of two double-lined binary stars KIC 5113146 and
KIC 5111815 in NGC 6819 is presented based on both photometric and
spectroscopic data. Simultaneous analysis of light and radial velocity curves
was made and the absolute parameters of the systems' components were determined
for the first time. We find that both systems have F-type main-sequence
components. The masses and radii were found to be $M_1=1.29\pm0.02 M_{\odot}$,
$R_{1}=1.47\pm0.03 R_{\odot}$ and $M_{2}=1.19\pm0.02 M_{\odot}$,
$R_{2}=1.13\pm0.02 R_{\odot}$ for the primary and secondary components of KIC
5113146; $M_{1}=1.51\pm0.08 M_{\odot}$, $R_{1}=2.02\pm0.05 R_{\odot}$ and
$M_{2}=1.19\pm0.07 M_{\odot}$, $R_{2}=1.32\pm0.04 R_{\odot}$ for components of
KIC 5111815, respectively. Evolutionary status of the components was evaluated
based on the MESA evolutionary tracks and isochrones. The ages of the KIC
5111815 and KIC 5113146 were derived to be about $2.50\pm0.35$ Gyr and
$1.95\pm0.40$ Gyr, respectively. Photometric distances were calculated to be
$2850\pm 185$ pc for KIC 5113146 and $3120\pm 260$ pc for KIC 5111815. The
results obtained in this study, astrometric data and researches in the
literature reveal that both KIC 5113146 and KIC 5111815 systems are the most
likely member of NGC 6819.
