Abstract

The EROS and MACHO collaborations have each published upper limits on the amount of planetary-mass dark matter in the Galactic halo obtained from gravitational microlensing searches. In this Letter, the two limits are combined to give a much stronger constraint on the abundance of low-mass MACHOs. Specifically, objects with masses 10 -7 M ? ? m ? 10 -3 M ? make up less than 25% of the halo dark matter for most models considered, and less than 10% of a standard spherical halo is made of MACHOs in the 3.5 × 10 -7 M ? < m < × 10 -5 M ? mass range. © 1998. The American Astronomical Society. All rights reserved.