http://arxiv.org/abs/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 $\sigma < 0.10$ 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 $(m-M_V)_0=18.41\pm0.20$ mag.
R. Grijs, X. Chen and L. Deng
Mon, 28 Nov 16
28/75
Comments: Invited talk; 5 pages, to appear in: The non-stable Universe: Energetic sources, activity phenomena and evolutionary processes, eds Mickaelian A., Harutyunian H., Nikoghosyan E., Byurakan (Armenia); ASP Conf. Ser
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