The MACHO Project: Microlensing Optical Depth Toward the Galactic Bulge from Difference Image Analysis

  title={The MACHO Project: Microlensing Optical Depth Toward the Galactic Bulge from Difference Image Analysis},
  author={Charles R. Alcock and Robyn A. Allsman and David Randall Alves and Timothy S. Axelrod and Andrew Cameron Becker and David P. Bennett and K. H. Cook and Andrew J. Drake and Kenneth C. Freeman and Marla Geha and Kim Griest and Matthew J. Lehner and Simon L. Marshall and Dante Minniti and Cailin Anne Nelson and Bruce A. Peterson and Piotr Popowski and Mark Robin Pratt and Peter Quinn and Christopher W. Stubbs and William J. Sutherland and Austin Bede Tomaney and Thor Vandehei and D. L. Welch},
  journal={The Astrophysical Journal},
We present the microlensing optical depth toward the Galactic bulge based on the detection of 99 events found in our Difference Image Analysis (DIA) survey. This analysis encompasses 3 yr of data, covering ~17 million stars in ~4 deg2, to a source-star baseline magnitude limit of V = 23. The DIA technique improves the quality of photometry in crowded fields, and allows us to detect more microlensing events with faint source stars. We find that this method increases the number of detection… 
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