[28.03] New Measurement of Microlensing Optical Depth and Examination of Blending in Microlensing Events

AAS 205th Meeting, 9-13 January 2005
Session 28 Lensing: Micro, MACHO, Strong, Weak and Wide
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[28.03] New Measurement of Microlensing Optical Depth and Examination of Blending in Microlensing Events

C.L. Thomas, K. Griest (UCSD), P. Popowski (Max-Planck-Institute), K.H. Cook (Lawrence Livermore National Laboratory), C. Alcock (Harvard-Smithsonian Center for Astrophysics), R.A. Allsman (NOAO), D.R. Alves (Goddard Space Flight Center), T.S. Axelrod (Steward Observatory), A.C. Becker (University of Washington), D.P. Bennett (Nore Dame), A.J. Drake (Pontifica Universidad Catolica), K.C. Freeman (Australian National University), M. Geha (Carnegie Observatories), M.J. Lehner (University of Pennsylvania), S.L. Marshall (KIPAC), D. Minniti (Pontifica Universidad Catolica), C.A. Nelson (Lawrence Livermore National Laboratory), B.A. Peterson (Australian National University), P.J. Quinn (European Southern Observatory), C.W. Stubbs (Harvard-Smithsonian Center for Astrophysics), W. Sutherland (Cambridge), T. Vandehei (UCSD), D. Welch (McMaster University), MACHO Collaboration

We present a new determination of the optical depth to microlensing to the Galactic bulge. We select a sample of 62 clump giant events (60 unique) and calulate the optical depth. With a detailed efficiency analysis we find \tau = 2.17_-0.38^+0.47\times 10^-6 at (l,b) = (1 .\!\!^\circ 50, -2 .\!\!^\circ 68). We also examine the problem of blending and whether it strongly effects our measurement. Photometric detection of blending is also examined. KG and CT were supported in part by the DoE under grant DEFG0390ER40546.

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