AAS Meeting #193 - Austin, Texas, January 1999
Session 108. Gravitational Lensing
Display, Saturday, January 9, 1999, 9:20am-4:00pm, Exhibit Hall 1

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[108.04] Results from Difference Image Analysis of Galactic Microlensing by the MACHO Collaboration

A. J. Drake, R. A. Allsman, T. S. Axelrod, K. C. Freeman, B. A. Peterson (MSO/ANU), C. Alcock, K. H. Cook, S. L. Marshall, D. Minniti, P. Popowski (LLNL), A. C. Becker, C. W. Stubbs, A. Tomaney (Washington), D. P. Bennett, L. J. King (Notre Dame), D. R. Alves (Berkley), K. Griest, T. Vandehei (UCSD), M. J. Lehner (Sheffield), M. R. Pratt (MIT), P. J. Quinn (ESO), W. Sutherland (Oxford), D. L. Welch (McMaster), MACHO Collaboration

For a number of years the MACHO collaboration has been probing the nature of the Galactic halo using microlensing events. The MACHO group undertakes observations of the LMC, SMC and Galactic Bulge, monitoring the light curves of millions of stars to detect microlensing. Most of the monitored fields are crowded to the extent that all the monitored stars are blended with neighbouring stars. This blending makes the performance of accurate photometry difficult.

We present results from the application of the Difference Image Analysis (DIA) technique to archival MACHO data. This technique allows us to improve the photometry in many cases and increase both the detection sensitivity and effective search area. The application of this technique has enabled us to detect so called `pixel lensing' events (microlensing events where the source star is only detectable during lensing) and has allowed us to increase the number of microlensing events detected toward the Galactic Bulge. We expect the application of this technique to LMC data should provide similar improvements in the near future.

The author(s) of this abstract have provided an email address for comments about the abstract: ajd@mso.anu.edu.au

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