  Cen X-3 shows alternate spin-up/spin-down episodes lasting for tens of days.
We study the orbital profiles and spectra of Cen X-3 during these
spin-up/spin-down intervals, using long-term data monitored by Fermi/GBM,
Swift/BAT and MAXI/GSC. In spin-up intervals, its orbital profile in 2-10 keV
is symmetrically peaked around orbital phase 0.42, while in spin-down intervals
of similar fluxes and similar magnitudes of spin change rate, its profile
reaches a peak around orbital phase 0.22 and then declines gradually. Such a
distinct orbital difference between spin-up and spin-down states of similar
flux is hard to explain in the standard disk model and indicates that its
torque reversals are related to processes on the orbital scale. The durations
of continuous spin-up/spin-down trend (tens of days) also point to a
superorbital variation. One possible scenario is the irradiation-driven warping
disk instability, which may produce a flipped inner disk for tens of days.
