LIMITS ON THE MACHOS FROM EROS-2

摘要

We present the results of the EROS-2 search for microlensing of stars in theMagellanic Clouds. Such events could be caused by macho dark matter in theMilky Way halo. Unlike all previous studies of Magellanic microlensing, we useonly a subsample of 7 x 106 bright stars. This strategy minimizes backgroundsdue to variable stars and ensures accurate determination of lensing parametersby minimizing source confusion (blending). Using this sample of bright stars,only one candidate event was found, whereas 42 events would have beenexpected if the Halo were entirely populated by objects of mass M 0.4M0.Combined with the results of EROS-1, this implies that the optical depthtoward the Large Magellanic Cloud (LMC) due to such lenses is T < 0.36 x 10-7(95%CL), corresponding to a fraction of the halo mass of less than 7%. Thislimit on the optical depth is at variance with the measurement of the MACHOcollaboration near the center of the LMC, implying that a significant fractionof their events are due to lenses in the LMC itself.