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Microlensing towards the Magellanic Clouds: Nature of the lenses and implications on dark matter

Published online by Cambridge University Press:  21 August 2009

Kailash C. Sahu
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; [email protected]
Mario Livio
Affiliation:
Space Telescope Science Institute, Baltimore
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Summary

A close scrutiny of the microlensing results towards the Magellanic clouds reveals that the stars within the Magellanic clouds are major contributors as lenses, and the contribution of MACHOs to dark matter is 0 to 5%. The principal results which lead to this conclusion are the following:

  1. (i) Out of the ∼17 events detected so far towards the Magellanic Clouds, the lens location has been securely determined for one binary-lens event through its caustic-crossing timescale. In this case, the lens was found to be within the Magellanic Clouds. Although less certain, lens locations have been determined for three other events and in each of these three events, the lens is most likely within the Magellanic clouds.

  2. (ii) If most of the lenses are MACHOs in the Galactic halo, the timescales would imply that the MACHOs in the direction of the LMC have masses of the order of 0.5 M, and the MACHOs in the direction of the SMC have masses of the order of 2 to 3 M. This is inconsistent with even the most flattened model of the Galaxy. If, on the other hand, they are caused by stars within the Magellanic Clouds, the masses of the stars are of the order of 0.2 M for both the LMC as well as the SMC.

  3. (iii) If 50% of the lenses are in binary systems similar to the stars in the solar neighborhood, ∼10% of the events are expected to show binary characteristics.

  4. […]

Type
Chapter
Information
The Dark Universe
Matter, Energy and Gravity
, pp. 14 - 23
Publisher: Cambridge University Press
Print publication year: 2004

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