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Microlensing events of the LMC are better explained by stars within the LMC than by MACHOs

1994; Institute of Physics; Volume: 106; Linguagem: Inglês

10.1086/133465

1538-3873

K. C. Sahu,

Astronomy and Astrophysical Research

For observations within the bar of the LMC, the probability of microlensing being caused by a star within the LMC is found to be ~5 x 10-8. Outside of the bar, the probability of microlensing being caused by a star in the LMC is 4 to 12 times lower. The event detected by Alock et al. and one of the events detected by Aubourg et al. lie well within the bar for which probability of microlensing is consistent with being caused by an object within the LMC. It is further shown that, under certain conditions, the light curve of an event caused by a star within the LMC would be different near the peak of the light curve from the one caused by a MACHO. This seems to be exactly what is observed in the event detected by Alcock et al. The fit discrepancy near the peak which the authors say "is not yet understood" would be a natural consequence if the event is caused by an object within the LMC, providing clear evidence that the lensing is due to a low mass star within the LMC itself. If the stars within the LMC play a dominant role as lenses, the events should be concentrated towards the center of the LMC. On the other hand, if MACHOs play a dominant role as lenses, then for a given number of monitored stars, the events should be more uniformly distributed over the whole area of the LMC.