The MACHO Project Constraints on Low Mass Machos in the Galactic Halo

Publication information:

M. J. Lehner, C. Alcock, R. A. Allsman, D. Alves, T. S. Axelrod, A. Becker, D. P. Bennett, K. H. Cook, K. C. Freeman, K. Griest, J. Guern, S. L. Marshall, B. A. Peterson, M. R. Pratt, P. J. Quinn, A. W. Rodgers, C. W. Stubbs, and W. Sutherland. 1996. “The MACHO Project Constraints on Low Mass Machos in the Galactic Halo”. Nuclear Physics B Proceedings Supplements, Vol. 51, 51, Pp. 141. doi:10.1016/S0920-5632(96)00495-1

Abstract

The MACHO project has been monitoring about ten million stars in the Large Magellanic Cloud in the search for gravitational microlensing events caused by massive compact halo objects (Machos) in the halo of the Milky Way. The standard analysis for well sampled, long duration microlensing is sensitive to objects with masses 10^-5 <~ m <~ 1M_solar. However, a different analysis method sensitive to short duration events extends the sensitivity of the experiment to lower masses. Combining the results of the analyses of the first two years of data from the LMC shows that Machos with masses in the range 2.5 × 10^-7 < m < 8.1 × 10^-2 M_solar cannot make up the entire mass of a standard spherical dark halo.