  A recent observational study suggests that the occurrence of hot Jupiters
(HJs) around solar-type stars is correlated with stellar clustering. We study a
new scenario for HJ formation, called "Flyby Induced High-e Migration", that
may help explain this correlation. In this scenario, stellar flybys excite the
eccentricity and inclination of an outer companion (giant planet, brown dwarf,
or low-mass star) at large distance (10-300 au), which then triggers high-e
migration of an inner cold Jupiter (at a few astronomical units) through the
combined effects of von Zeipel-Lidov-Kozai (ZLK) eccentricity oscillation and
tidal dissipation. Using semianalytical calculations of the effective ZLK
inclination window, together with numerical simulations of stellar flybys, we
obtain the analytic estimate for the HJ occurrence rate in this formation
scenario. We find that this "flyby induced high-e migration" could account for
a significant fraction of the observed HJ population, although the result
depends on several uncertain parameters, including the density and lifetime of
birth stellar clusters, and the occurrence rate of the "cold Jupiter + outer
companion" systems.
