Gravitational microlensing of the Galactic bulge stars

The Optical Gravitational Lensing Experiment (OGLE, Udalski et al. 1994a; Paczynski et al. 1994b – these proceedings; and references therein) is an extensive photometric search for the rare cases of gravitational microlensing of Galactic bulge stars by foreground objects. It provides a huge data base (Szymański & Udalski 1993), from which color-magnitude diagrams have been compiled (Udalski et al. 1993, 1994b). Here we discuss the use a of well-defined population of bulge red clump stars to investigate the presence of the bar in our Galaxy. The results of our earlier studies are described by Stanek et al. (1994).

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Spatial/Spectral Resolution of a Galactic Bulge K3 Giant Stellar Atmosphere via Gravitational Microlensing

The Astrophysical Journal ◽

10.1086/319108 ◽

2001 ◽

Vol 548 (2) ◽

pp. L197-L200 ◽

Cited By ~ 24

Author(s):

Sandra Castro ◽

Richard W. Pogge ◽

R. Michael Rich ◽

D. L. DePoy ◽

Andrew Gould

Keyword(s):

Spectral Resolution ◽

Stellar Atmosphere ◽

Galactic Bulge ◽

Gravitational Microlensing

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The MOA Project Data Reduction Pipeline and Database

International Astronomical Union Colloquium ◽

10.1017/s0252921100057171 ◽

2000 ◽

Vol 176 ◽

pp. 78-79

Author(s):

M. L. Reid ◽

D. J. Sullivan ◽

R. J. Dodd

Keyword(s):

New Zealand ◽

Data Processing ◽

Data Reduction ◽

Magellanic Clouds ◽

Galactic Bulge ◽

Primary Motivation ◽

Data Processing Software ◽

Gravitational Microlensing ◽

Processing Software ◽

Project Data

AbstractThe MOA Project is a collaboration of Japanese and New Zealand (NZ) astronomers and physicists undertaking a survey of stellar variability in the direction of the Galactic bulge and Magellanic Clouds. The primary motivation of the project is detection and monitoring of gravitational microlensing events although a large amount of data is also collected on stellar variability. Surveying the number of stars required to detect gravitational microlensing events is an operation of some magnitude and requires sophisticated data processing software.

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Gravitational Microlensing, The Distance Scale, And The Ages

Symposium - International Astronomical Union ◽

10.1017/s0074180900231306 ◽

1996 ◽

Vol 173 ◽

pp. 199-208 ◽

Cited By ~ 1

Author(s):

Bohdan Paczyński

Keyword(s):

Optical Depth ◽

Globular Clusters ◽

Age Determination ◽

Variable Stars ◽

Conclusive Evidence ◽

Compact Objects ◽

Eclipsing Binaries ◽

Galactic Bulge ◽

Gravitational Microlensing

A high optical depth to gravitational microlensing towards the galactic bulge is consistent with current models of the galactic bar. The low optical depth towards the LMC can probably be accounted for by the ordinary stars in our galaxy and in the LMC itself. No conclusive evidence is available yet for the presence or absence of a large number of brown dwarfs or other non-stellar compact objects which might account for the dark matter. There is little doubt that the amount of mass in objects in the range 10–8 ≤ M/M⊙ ≤ 106 will be determined within the next few years with the continuing and expanding searches.Billions of photometric measurements generated by the microlensing searches have lead to the discovery of ∼ 105 variable stars. In particular, a number of detached eclipsing binaries were discovered in the galactic bulge, in the LMC, and in the globular cluster Omega Centauri. The follow-up observations of these binaries will allow the determination of accurate distances to all these objects, as well as robust age determination of globular clusters.

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Modelling the Galactic Bar using Red Clump Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100050405 ◽

1996 ◽

Vol 157 ◽

pp. 545-548 ◽

Cited By ~ 2

Author(s):

K. Z. Stanek ◽

M. Mateo ◽

A. Udalski ◽

M. Szymański ◽

J. Kałuzny ◽

...

Keyword(s):

Line Of Sight ◽

Galactic Bulge ◽

Preliminary Results ◽

Gravitational Microlensing ◽

Luminosity Functions ◽

Red Clump ◽

Additional Constraints ◽

Galactic Longitude

AbstractThe color-magnitude diagrams of ~ 1 × 106 stars obtained for 19 fields towards the Galactic bulge with the OGLE project 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 ι = ±5° in galactic longitude differ by ∼ 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°. 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 ∼ 20°. Gravitational microlensing can provide us with additional constraints on the structure of the Galactic bar.

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