OGLE-2019-BLG-1470LABc: Another Microlensing Giant Planet in a Binary
  System
  We report the discovery and analysis of a triple-lens single-source (3L1S)
microlensing event, OGLE-2019-BLG-1470. This event was first classified as a
normal binary-lens single-source (2L1S) event, but a careful 2L1S modelling
showed that it needs an additional lens or source to fit the observed data. It
is found that the 3L1S model provides the best fit. The binary-lens
binary-source (2L2S) model is excluded by $\Delta\chi^2 = 47$ and is also
strong disfavored by its unreasonably small lens-source relative proper motion
$\mu_{rel} \sim 0.8~{mas,yr^{-1}}$. We find that four 3L1S solutions can fit
the observed data, and all of them contain a planet in a binary system. A
Bayesian analysis based on a Galactic model indicates that the planet is
super-Jovian and the binary stars are likely two M or K dwarfs. The projected
primary-planet separation is about 3 AU. By investigating the properties of all
microlensing planets in binary systems, we find another "missing planetary
caustics" problem in the KMTNet planetary simple. A systematic KMTNet planetary
anomaly search for planets in binary systems is needed.
