No abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

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 paper 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 < 4.5 × 10 −5 M ⊙ mass range.

Abstract. We present a measurement of the microlensing optical depth toward the Galactic bulge based on the analysis of 15 contiguous 1 deg 2 fields centered on (l = 2.• 5, b = −4.• 0) and containing N * = 1.42 × 10 6 clump-giant stars (belonging to the extended clump area) monitored during almost three bulge seasons by EROS (Expérience de Recherche d'Objets Sombres). We find τ bulge = 0.94 ± 0.29 × 10 −6 averaged over all fields, based on 16 microlensing events with clump giants as sources. This value is substantially below several other determinations by the MACHO and OGLE groups and is more in agreement with what is expected from axisymmetric and non-axisymmetric bulge models.

Abstract. Five years of  data towards the Small Magellanic Cloud have been searched for gravitational microlensing events, using a new, more accurate method to assess the impact of stellar blending on the efficiency. Four long-duration candidates have been found which, if they are microlensing events, hint at a non-halo population of lenses. Combined with results from other  observation programs, this analysis yields strong limits on the amount of Galactic dark matter made of compact objects. Less than 25% of a standard halo can be composed of objects with a mass between 2 × 10 −7 M and 1 M at the 95% C.L.