Online detection of gravitational microlensing with the EROS2 experiment

The EROS2 acquisition system and software trigger are presented in this paper. The acquisition system was designed for EROS1 and turned out to be modular enough to be reused (with some minor changes) with a completely different hardware and a different observing strategy. It is based on the OS9 operating system and gives a full control of the experiment. The software trigger is done in 3 steps: photometry on a subsample of the data, filtering and finally an interactive validation of the candidates. The performances of the trigger are presented.