Difference image analysis of galactic microlensing. II. Microlensing events

C. Alcock, R. A. Allsman, D. Alves, T. S. Axelrod, A. C. Becker, D. P. Bennett, K. H. Cook, A. J. Drake, K. C. Freeman, K. Griest, M. J. Lehner, S. L. Marshall, D. Minniti, B. A. Peterson, M. R. Pratt, P. J. Quinn, C. W. Stubbs, W. Sutherland, A. Tomaney, T. VandeheiD. L. Welch

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


The MACHO collaboration has been carrying out difference image analysis (DIA) since 1996 with the aim of increasing the sensitivity to the detection of gravitational microlensing. This is a preliminary report on the application of DIA to galactic bulge images in one field. We show how the DIA technique significantly increases the number of detected lensing events, by removing the positional dependence of traditional photometry schemes and lowering the microlensing event detection threshold. This technique, unlike PSF photometry, gives the unblended colors and positions of the microlensing source stars. We present a set of criteria for selecting microlensing events from objects discovered with this technique. The 16 pixel and classical microlensing events discovered with the DIA technique are presented.

Original languageEnglish
Pages (from-to)171-179
Number of pages9
JournalAstrophysical Journal, Supplement Series
Issue number1
Publication statusPublished - Sept 1999


  • Atmospheric effects
  • Galaxy: stellar content
  • Gravitational lensing
  • Techniques: image processing

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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