A Puzzle Involving Galactic Bulge Microlensing Events
We study a sample of 16 microlensed Galactic bulge main-sequence turnoff region stars for which high-dispersion spectra have been obtained with detailed abundance analyses. We demonstrate that there is a very strong and highly statistically significant correlation between the maximum magnification of the microlensed bulge star and the value of the [Fe/H] deduced from the high resolution spectrum of each object. Physics demands that this correlation, assuming it to be real, be the result of some sample bias. We suggest several possible explanations, but are forced to reject them all, and are left puzzled. To obtain a reliable metallicity distribution in the Galactic bulge based on microlensed dwarf stars, it will be necessary to resolve this issue through the course of additional observations.
Additional Information© 2010 The American Astronomical Society. Received 2009 November 26; accepted 2010 January 27; published 2010 February 11. We are grateful to the many people who have worked to make the Keck Telescope and HIRES a reality and to operate and maintain the Keck Observatory. The authors wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests.Without their generous hospitality, none of the observations presented herein would have been possible.We thank Chris Hirata and Sterl Phinney for helpful discussions. J.G.C. thanks NSFgrantsAST-0507219 and AST-0908139 for partial support. Work by A.G. was supported by NSF grant AST-0757888. I.B.T. thanks NSF grant AST-0507325 for support.
Published - Cohen2010p7407Astrophys_J_Lett.pdf
Submitted - 0911.5081.pdf