OBJECT DUO-2 - A NEW BINARY LENS CANDIDATE

We present the light curve of an unusual variable object, DUO 2, detec ted during the search for microlensing events by the DUO project. The star remained stable for more than 150 days before it brightened by mo re than two magnitudes in 6 days in the B and R bands. The light curve s are achromatic during the variability. We con sider possible explana tions of the photometric behavior, with particular emphasis on the bin ary lens interpretation of the event. The masses of the lenses are qui te small, with the companion possibly in the range of a brown dwarf or even a few times of Jupiter. We report evidence of blending of the so urce by a companion through the first detection of shift in the light centroid among all the microlensing experiments. This shift sets a low er limit of 0.3'' on the separation between the stars. The best lens m odel obtained requires moderate blending, which was what motivated us to check the centroid shift that was subsequently found. The best lens model predicts a separation of 1'' between the two blended stars. Thi s prediction was recently tested using two CCD images taken under good seeing conditions. Both images show two components. Their separation and position angle are in good agreement with our model.