Stellar Contribution to the Galactic Bulge Microlensing Optical Depth

By C. Han, A. Gould. 2003

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We estimate the optical depth to self-lensing by stars in the Galactic bulge using the Hubble Space Telescope star counts of Holtzman et al. and Zoccali et al. as extrapolated by Gould into the brown dwarf and remnant regimes and deprojected along the line of sight using the model of Dwek et al. We find a self-lensing optical depth τ(bulge - bulge) = 0.98 × 10-6. When combined with the lensing of bulge stars by foreground stars in the disk, this yields τ(bulge - total) = 1.63 × 10-6, in reasonable agreement with the estimates of τ = 2.13 ± 0.40 × 10-6 and τ = 1.08 ± 0.30 × 10-6 based on observations of clump giants by the MACHO and EROS collaborations.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9c083abf07d59a38b699ade6f8cba8389d79709f

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Citations in the corpus

Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds (2006, result): “The measured optical depth is in agreement with that measured by MACHO (Popowski et al. 2005), and OGLE-2 (Sumi et al. 2006) and with the predictions of Galactic models (Evans & Belokurov 2002; Bissantz & Gerhard 2002; Han & Gould 2003; Wood & Mao 2005).”
MOA-2009-BLG-387Lb: a massive planet orbiting an M dwarf (2011, methodology): “For the bulge, Han & Gould (2003) normalize the “G2” K-band integrated-light-based bar model of Dwek et al. (1995) using star counts toward Baade’s window from Holtzman et al. (1998) and Zoccali et al. (2000).”
OGLE-2003-BLG-262: Finite-Source Effects from a Point-Mass Lens (2003, methodology): “We adopt the Han & Gould (1995, 2003) model, and in Figure 6 we plot πrel(M)P[πrel(M)] versus logM to display the constraint placed on the mass by the measurement ofθE.”
Microlens OGLE-2005-BLG-169 Implies That Cool Neptune-like Planets Are Common (2006, unknown): “These measurements, together with a Bayesian prior for the lens distances and masses from a Han & Gould (2003) Galaxy model and Gould (2000) mass function (but with a Salpeter [−2.35] slope at the high end), together with the assumption that all stellar objects along the line of sight are equally…”
A COLD NEPTUNE-MASS PLANET OGLE-2007-BLG-368Lb: Cold neptunes are common (2009, methodology): “(22) To produce the likelihood distributions shown in Figure 7, we compute the likelihood by combining this equation and the measured values of θE and tE with the Galactic model (Han & Gould 2003) assuming the distance to the GC is 8 kpc.”