AAS 207th Meeting, 8-12 January 2006
Session 135 A New Look at Andromeda
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[135.07] HST Imaging of MEGA Microlensing Candidates in M31

P. Cseresnjes, A. Crotts, A. Bergier (Columbia Astrophysics Laboratory), J. de Jong (Kapteyn Insitute), E. Baltz (Stanford University), G. Gyuk (University of Chicago), K. Kuijken (University of Leiden), L. Widrow (Queens University)

The positions of five microlensing candidate events from a large survey of variability in M31 (MEGA) have been studied in detail on HST/ACS and WFPC2 images. While three of these events closely match unresolved sources, two of them provide only upper limits on the flux. In each case we can exclude variables as improbable due to their location on the color-magnitude diagram. In two cases a background supernova is possible. If the lenses are located in the halo of M31, their masses are 0.15 < m/Msun < 0.49, with 95 certainty (for a delta-function distribution); disk lenses would be brown dwarfs and bulge lenses of stellar masses.

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