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The optical depth to gravitational microlensing in the direction of the galactic bulge

Jul, 1994
19 pages
Published in:
  • Acta Astron. 44 (1994) 165-189
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Abstract: (arXiv)
We present the analysis of the first two years of the OGLE search for gravitational lenses towards the Galactic bulge. We detected 9 microlensing events in an algorithmic search of ∼108 \sim 10^8 measurements of ∼106 \sim 10^6 stars. The characteristic time scales are in the range 8.6<t0<62 8.6 < t_0 < 62 days, where t0=RE/V t_0 = R_E / V . The distribution of amplitudes is consistent with theoretical expectation. The stars seem to be drawn at random from the overall distribution of the observed bulge stars. We find that the optical depth to microlensing is larger than (3.3±1.2)×10−6 ( 3.3 \pm 1.2 ) \times 10^{-6}, in excess of current theoretical estimates.
  • DARK MATTER
  • GRAVITATIONAL LENSING
  • STARS
  • LOW-MASS, BROWN DWARFS