AAS 207th Meeting, 8-12 January 2006
Session 142 Gravitational Lensing
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[142.03] Solving the Microlensing Puzzle: A Spitzer/IRAC Approach

B.M. Patten, N. Kallivayalil, C. Alcock (CfA), M.W. Werner (JPL/Caltech), G.G. Fazio (CfA)

We have used the Infrared Array Camera (IRAC) on the Spitzer Space Telescope to obtain near/mid-IR imaging for 10 bona-fide Large Magellanic Cloud microlensing events seen in the original MACHO survey. These data were acquired as part of a survey to ascertain the basic characteristics of the stellar population responsible for the gravitational microlensing and thus to assess what fraction of these events have lenses which belong to some population of dwarf stars in the disk of our own galaxy and what fraction must be due to lenses in the halo or in the LMC itself. For the IRAC survey data, a cool lens star in the disk would be revealed in the IRAC bandpasses via an infrared flux excess, a technique we have already used to show that the lens of event MACHO-LMC-5 is an ~M5 dwarf in a related GTO program (Kallivayalil et al. 2004, AAS 204, 4121; Nguyen et al. 2004, ApJS 154, 266; Kallivayalil et al. 2004, AAS 205, 2801). We will present initial results of our analysis of these new data which complete the Spitzer/IRAC portion of our LMC microlensing survey. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for the IRAC instrument was provided by NASA under contract number 1256790 issued by JPL.

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