First Results Of The DUO Program

Abstract

The DUO (Disk Unseen Objects) program is a project with the main goal of searching for galactic dark matter in a field towards the Galactic Bulge (Alard et al. 1995b). In this paper I present the results obtained from the analysis of half of the data collected during the 1994 season. I start with a brief description of the DUO project, and I will continue with an analysis of the microlensing candidates that I found. In all I found 13 microlensing events in the DUO data, including a double lens event. A model of the double lens light curve predicts a blending effect. The presence of the blended component was confirmed by a gravity center shift during the event. Taking into account the model prediction and the shift, we could predict the exact geometry of the blend. This prediction was recently confirmed by direct imaging of the blend under good seeing conditions. The durations of the single lens events are quite short, but the durations can be seriously affected by blending. I propose a simple experimental test to quantify this duration bias. In the conclusion I emphasize the great importance of a good knowledge of the inner Galactic structure to get a reliable quantitative description of microlensing towards the bulge. Finally I will show that the large number of variables stars found in the data could be a powerful tool to probe this structure.