The end of the MACHO era- revisited: new limits on MACHO masses from
  halo wide binaries
  In order to determine an upper bound for the mass of the massive compact halo
objets (MACHOs) we use the halo binaries contained in a recent catalog (Allen
\& Monroy-Rodr\'{\i}guez 2013). To dynamically model their interactions with
massive perturbers a Monte Carlo simulation is conducted, using an impulsive
approximation method and assuming a galactic halo constituted by massive
particles of a characteristic mass. The results of such simulations are
compared with several subsamples of our improved catalog of candidate halo wide
binaries. In accordance with Quinn et al. (2009) we also find our results to be
very sensitive to the widest binaries. However, our larger sample, together
with the fact that we can obtain galactic orbits for 150 of our systems, allows
a more reliable estimate of the maximum MACHO mass than that obtained
previously. If we employ the entire sample of 211 candidate halo stars we
obtain an upper limit of $112 M_\sun$. However, using the 150 binaries in our
catalog with computed galactic orbits we are able to refine our fitting
criteria. Thus, for the 100 most halo-like binaries we obtain a maximum MACHO
mass of $21-68 M_\sun$. Furthermore, we can estimate the dynamical effects of
the galactic disk using binary samples that spend progressively shorter times
within the disk. By extrapolating the limits obtained for our most reliable
-albeit smallest- sample we find that as the time spent within the disk tends
to zero the upper bound of the MACHO mass tends to less than $5 M_\sun$. The
non-uniform density of the halo has also been taken into account, but the limit
obtained, less than $5 M_\sun$, does not differ much from the previous one.
Together with microlensing studies that provide lower limits on the MACHO mass,
our results essentially exclude the existence of such objects in the galactic
halo.
