The Wendelstein Calar Alto Pixellensing Project (WeCAPP): First MACHO Candidates

We report the detection of the first 2 microlensing candidates from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). Both are detected with a high signal-to-noise-ratio and were filtered out from 4.5 mill. pixel light curves using a variety of selection criteria. Here we only consider well-sampled events with timescales of 1d < t fwhm < 20d, high amplitude, and low of the microlensing fit. The two-color photometry (R; I) shows that the events are achromatic and that giant stars with colors of (R- I) 1:1mag in the bulge of M31 have been lensed. The magnification factors are 64 and 10 which are obtained for typical giant luminosities of M I = -2:5mag. Both lensing events lasted for only a few days (t = 1:7d and t = 5:4d). The event GL1 is likely identical with PA-00-S3 reported by the POINT-AGAPE project. Our calculations favor in both cases the possibility that MACHOs in the halo of M31 caused the lensing events. The most probable masses, 0:08M for GL1 and 0:02M for GL2, are in the range of the brown dwarf limit of hydrogen burning. Solar mass objects are a factor of two less likely.

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