Real-time detection and multisite observations of gravitational microlensing

The MACHO collaboration is carrying out an extensive survey to detect gravitational microlensing. We have recently demonstrated the ability to detect candidate microlensing events in real time, often well before the peak amplification of the event. This has made possible the acquisition of spectra over the course of an event, the invariance of which has lent strong support to the microlensing interpretation. This paper reports, on photometric …