2016/11/25 by Richard de Grijs, Xiaodian Chen, de Grijs, Richard +3
Physics and Astronomy · #Stellar, planetary, and galactic studies #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies
paper · pdf · doi:10.48550/arxiv.1611.08409
We used the 50 cm Binocular Network (50BiN) telescope at Delingha Station (Qinghai Province) of Purple Mountain Observatory (Chinese Academy of Sciences) to obtain simultaneous V- and R-band observations of the old open cluster NGC 188. Our aim was a search for populations of variable stars. We derived light-curve solutions for six W Ursae Majoris (W UMa) eclipsing-binary systems and estimated their orbital parameters. The resulting distance to the W UMas is independent of the physical characteristics of the host cluster. We next determined the current best period--luminosity relations for contact binaries (CBs; scatter σ< 0.10 mag). We conclude that CBs can be used as distance tracers with better than 5% uncertainty. We apply our new relations to the 102 CBs in the Large Magellanic Cloud, which yields a distance modulus of (m-MV)0=18.41±0.20 mag.