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Session 59 - Milky Way, Center & Halo.
Oral session, Tuesday, January 16
Salon del Rey Central, Hilton

[59.03] Modelling the Galactic Bar Using Red Clump Stars

K. Z. Stanek (Princeton U.), M. Mateo (U. Michigan), A. Udalski, M. Szyma\'nski, J. K. uzny, M. Kubiak (Warsaw U.), W. Krzemi\'nski (Carnegie Obs.)

The color-magnitude diagrams of \sim 1 \times 10^6 stars obtained for 20 fields across the Galactic bulge by the Optical Gravitational Lensing Experiment (OGLE) collaboration reveal a well-defined population of bulge red clump stars. We found that the distributions of the extinction-adjusted apparent magnitudes of red clump stars in fields lying at l=\pm5\deg in galactic longitude differ by \sim 0.4\; mag. A plausible explanation of this observed difference in the luminosity distribution is that the Galactic bulge is a triaxial structure, or a bar, which is inclined to the line of sight by no more than 45\deg. The part of the bar at the positive galactic longitude is closer to us.

Work is now under way to model the Galactic bar by fitting the observed luminosity functions in the red clump region for various fields. Preliminary results indicate that the angle of the inclination of the bar to the line of sight can be as small as \sim20\deg. Gravitational microlensing can provide us with additional constrains on the structure of the Galactic bar.

Program listing for Tuesday