  Ultra-short period planets provide a window into the inner edge of the
parameter space occupied by planetary orbits. In one particularly intriguing
class of multi-planet systems, the ultra-short period planet is flanked by
short-period companions, and the outer planets occupy a discernibly distinct
dynamical state. In the observational database, this phenomenon is represented
by a small number of stars hosting systems of tightly packed co-planar planets
as well as an ultra-short period planet, whose orbit of is misaligned relative
to the mutual plane of the former. In this work, we explore two different
mechanisms that can produce an ultra-short period planet that is misaligned
with the rest of its compact planetary system: natural decoupling between the
inner and outer system via the stellar quadrupole moment, and decoupling forced
by an external companion with finely-tuned orbital parameters. These two
processes operate with different timescales, and can thus occur simultaneously.
In this work, we use the K2-266 system as an illustrative example to elucidate
the dynamics of these two processes, and highlight the types of constraints
that may arise regarding the dynamical histories of systems hosting ultra-short
period planets.
