  X-ray photometry and optical spectra are presented covering the periastron
passage of the highly-eccentric, ~50 year binary system PSR J2032+4127 in
November 2017. This system consists of a 143 ms pulsar in orbit around a
massive OB star, MT 91-213. The data show dramatic changes during the encounter
as the pulsar wind collided with the stellar wind. The X-ray flux rose on the
approach to periastron, then underwent a major dip in the few days around
periastron, and then gradually declined over the next few weeks. The optical
spectroscopy revealed a steady decline in the H? line strength on the approach
to periastron (from an Equivalent Width of -15A to -7A) implying a truncation
of the OB star's circumstellar disk by the approaching neutron star. Smooth
Particle Hydrodynamic (SPH) modelling is used here to model the system within
the context of the observed behaviour and predict the geometrical configuration
of the circumstellar disk with respect to the pulsar's orbit.
