The WIYN Open Cluster Study Photometric Binary Survey: Initial Findings for NGC 188
Nielsen, Danielle ( Colby College ); Frinchaboy, P. ( University of Wisconsin-Madison ) show affiliations
American Astronomical Society, AAS Meeting #211, #58.23; Bulletin of the American Astronomical Society, Vol. 39, p.837
Published in Dec 2007
The WIYN open cluster study (WOCS) has been working to yield precise optical (UBRVI) photometry for all stars in the field of a selection of "prototypical" open clusters. Additionally, WOCS has been using radial velocities to obtain orbit solutions for cluster member hard-binary stars (with period less than 1000 days). Recently, WOCS has been expanded to include the near-infrared JHKs (2MASS plus new deep ground-based) and mid-infrared ([3.6], [4.5], [5.8], [8.0] micron) photometry from Spitzer/IRAC observations. This multi-wavelength data (0.3 to 8.0 microns) allows us to identify binaries photometrically, with mass ratios from 1.0 to 0.3, across a wide range of primary masses. The spectral energy distribution (SED) fitter by Robitaille et al. (2007) is used to fit the fluxes of 10 to 12 bands to Kurucz stellar models. This technique allows us to explore the soft, long-period binary population for the first time. Using this photometric technique, we find that NGC 188 has a binary fraction of 36-49% and provide a star-by-star comparison to the WOCS radial velocity-based hard, short-period binary study.This work was supported by the REU and ASSURE programs through NSF award AST-0453442 and by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0602221.