  Despite decades of inquiry, the origin of giant planets residing within a few
tenths of an astronomical unit from their host stars remains unclear.
Traditionally, these objects are thought to have formed further out before
subsequently migrating inwards. However, the necessity of migration has been
recently called into question with the emergence of in-situ formation models of
close-in giant planets. Observational characterization of the transiting
sub-sample of close-in giants has revealed that "warm" Jupiters, possessing
orbital periods longer than roughly 10 days more often possess close-in,
co-transiting planetary companions than shorter period "hot" Jupiters, that are
usually lonely. This finding has previously been interpreted as evidence that
smooth, early migration or in situ formation gave rise to warm Jupiter-hosting
systems, whereas more violent, post-disk migration pathways sculpted hot
Jupiter-hosting systems. In this work, we demonstrate that both classes of
planet may arise via early migration or in-situ conglomeration, but that the
enhanced loneliness of hot Jupiters arises due to a secular resonant
interaction with the stellar quadrupole moment. Such an interaction tilts the
orbits of exterior, lower mass planets, removing them from transit surveys
where the hot Jupiter is detected. Warm Jupiter-hosting systems, in contrast,
retain their coplanarity due to the weaker influence of the host star's
quadrupolar potential relative to planet-disk interactions. In this way, hot
Jupiters and warm Jupiters are placed within a unified theoretical framework
that may be readily validated or falsified using data from upcoming missions
such as TESS.
