New limits from microlensing on Galactic Black Holes in the mass range 10xMsun

We have searched for long duration microlensing events originating from intermediate mass Black Holes (BH) in the halo of the Milky Way, using archival data from EROS-2 and MACHO photometric surveys towards the Large Magellanic Cloud. We combined data from these two surveys to create a common database of light curves for 14.1 million objects in LMC, covering a total duration of 10.6 years, with flux series measured through 4 wide band filters. We have carried out a microlensing search on these light curves, complemented by 22.7 million light curves, observed by EROS-2 only or MACHO only over about 7 years, with flux series measured through only 2 filters. A likelihood analysis, taking into account LMC self lensing and Milky Way disk contributions allows us to conclude that compact objects with masses in the range 10 − 100M cannot make up more than ∼ 15% of a standard halo total mass (at 95% confidence level). Our analysis sensitivity weakens for heavier objects, although we still exclude that ∼ 50% of the halo be made of ∼ 1000M BHs. Combined with previous EROS results, an upper limit of ∼ 15% of the total halo mass can be obtained for the contribution of compact halo objects in the mass range 10−6 − 102 M .