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E. Sandquist (San Diego State U.), M. Shetrone (U. Texas/McDonald Obs.), M. Blake (David Dunlop Obs.)
We present light-curve analyses for two binary stars at the turnoff of the old open cluster M67. Both systems show total eclipses that strongly constrain the inclinations to be near 90 degrees, and confirm that the companions are main sequence stars of much lower mass. In addition, both systems are known to show two radial velocity components in lines in their spectra, making accurate determinations of component masses possible. One of the systems is the W UMa contact binary S1282 (AH Cnc), which was discovered to have total eclipses by Gilliland et al. (1991), and which is shown to have a mass ratio q = 0.17. The other system is the non-interacting detached binary S986, having a period near 10.33 d. A secondary eclipse has not been detected, confirming that the secondary is a much fainter star (Mathieu et al. 1990). We have refined the ephemeris of Mathieu et al. using a combination of radial-velocity and photometry data spanning more than 18 years. For both systems, the primary star is expected to have a mass very close to that of single stars at the cluster turnoff, thus providing the excellent opportunity to calibrate the age of this important cluster.
The author(s) of this abstract have provided an email address for comments about the abstract: erics@mintaka.sdsu.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.