First Space-based Microlens Parallax Measurement: Spitzer Observations Of OGLE-2005-SMC-001
Abstract
We make the first space-based microlens parallax measurement since Refsdal proposed the idea in 1966. We combine Spitzer and ground-based observations to measure the microlens parallax of OGLE-2005-SMC-001, which yields a projected velocity 230 km/s. This is a typical value expected for halo lenses, but an order of magnitude smaller than would be expected for lenses lying in the Small Magellanic Cloud (SMC) itself. The lens is a weak (i.e., non-caustic-crossing) binary, which complicates the analysis considerably but ultimately contributes additional constraints. Using a test which makes use only of kinematic information about different populations but does not make any assumptions about their respective mass functions, we find that the lens is 20 times more likely to be located in the Milky Way halo than in the SMC. Hence, halo lenses are strongly favored but SMC lenses are not definitively ruled out. Similar Spitzer observations of additional lenses toward the Magellanic Clouds would clarify the nature of the lens population. The Space Interferometry Mission could make even more constraining measurements.
- Publication:
-
American Astronomical Society Meeting Abstracts #210
- Pub Date:
- July 2007
- Bibcode:
- 2007AAS...21012111D