STARS WITHIN THE LARGE MAGELLANIC CLOUD AS POTENTIAL LENSES FOR OBSERVED MICROLENSING EVENTS

MASSIVE compact objects in the Galactic halo, known as MACHOs, have be en postulated as the origin of a substantial fraction of the 'dark mat ter' known to exist in the haloes of galaxies(1,2). Paczynski(3) has s uggested that it might be possible to detect these low-luminosity obje cts by their potential to act as gravitational lenses, causing a chara cteristic brightening when they cross the path of light from a star in a nearby galaxy. Very recently, two groups reported possible detectio ns of microlensing of stars in the Large Magellanic Cloud (LMC)(4,5), which was interpreted as a possible fingerprint of MACHOs. Here I show that microlensing by stars within the LMC itself can account for the observed events. In the future it should be possible to distinguish be tween the two possible sources of microlensing events, however, becaus e events caused by stars in the LMC should be clustered toward the cen tral region of that galaxy,whereas those caused by MACHOs should be un iformly distributed over the whole LMC.