After a decade of gravitational microlensing experiments, a dozen microlensing candidates in the direction of the stars of the Large Magellanic Cloud (LMC) have been detected by the EROS and MACHO groups. Recently it was shown that the distribution of the duration of the observed LMC microlensing events is significantly narrower than what is expected from the standard halo model. In this article we make the same comparison, using non-standard halo models and considering the contribution of non-halo components of the Milky Way such as the disc, spheroid and the LMC itself in the microlensing events. Comparing the theoretical and experimental widths of the distribution of the duration of events shows that neither standard nor non-standard halo models are compatible with the microlensing data at least with 95 per cent confidence. These results may be explained if (i) the MACHOs in the Galactic halo reside in clumpy structures or (ii) the durations of events have been underestimated due to the blending effect.
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2004
- galaxies: haloes;
- dark matter;
- 13 pages, 4 figures, accepted in Mon.Not.Roy.Astron.Soc