  Short version: Zaritsky and Lin (1997, ZL97) have recently presented
observations which can be interpreted as evidence for an intervening stellar
population along the line-of-sight to the LMC, at a distance of ~34 kpc. They
suggest that it may belong to a low surface-brightness dwarf galaxy, or to the
tidal debris of a disrupted galaxy, and derive an optical depth for
gravitational lensing through the intervening system which is consistent with
the observed value. Such interpretation of the microlensing events toward the
LMC has major implications for the nature of the dark matter, and thus should
be tested in every conceivable way.
  We suggest a method utilizing the microlensing data themselves to
discriminate between the various hypotheses. We find that the first eight MACHO
events toward the LMC are as consistent with a standard halo distribution of
0.5 solar-mass MACHOs (best fit), as they are with an intervening population
having a transverse speed of ~240 km/s and a Miller-Scalo stellar IMF. Monte
Carlo simulations show that in order to completely rule out either hypothesis,
about 40 events will be required if the IMF is rising below the H-burning mass
limit, and about 140 if it is falling. If the ZL97 intervening population
hypothesis is correct then: (a) the currently observed range of event durations
directly implies a lens mass range of ~0.06-0.8 solar-mass, which brackets the
mass of ~0.2 solar mass where many investigations claim that the stellar IMF
peaks, and (b) the event distribution provides valuable information on the
low-mass end of the stellar IMF.
