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M. Shetrone (University of Texas, McDonald Observatory), S. Warren, E. Sandquist (San Diego State University)
M67 is an old (~\ 4 Gy; Dinescu et al. 1995) relatively close (V-MV ~ 9.7; Dinescu et al. 1995) open cluster that allows us to easily acquire photometric and spectroscopic data. To date there has never been a survey of all the blue straggler stars (BSSs) in any cluster using both spectroscopic and photometric data. We have done this for all but three of the known BSSs of M67. Using the Hobby-Eberly 9.2 m Telescope (HET) and the 2.7 m Harlan J. Smith Telescope we obtained high resolution spectroscopic data for each star and the 1 m telescope at the Mount Laguna Observatory to acquire photometric data. We found radial and rotational velocities as well as photometric temperatures for each star. An interesting trend between color and rotational velocity shows that bluer stars usually have higher velocities. Three stars showing no signs of binarity have been found to have radial velocities unlike the mean radial velocity of M67 (~ 34 km/s) making them most likely non-members of the cluster although proper motion studies give them high probabilities of membership. Abundance analysis has also been done for the reddest BSSs (V-I > 0.555) in order to find other information about each star such as surface gravity, temperature, microturbulance and metallicity. One element in particular, lithium, was scrutinized because it has been theorized that it should remain in the atmospheres of some of the cooler (redder) BSSs. We find absolutely no evidence of lithium in any unquestionable BSS and propose that lithium does not exist in the atmospheres of the BSSs of M67.
This work was supported by the National Science Foundation under Grant No. 0243745
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.