  We conduct a spectro-polarimetric study of the accreting X-ray pulsar
Hercules X-1 using observations with the Imaging X-ray Polarimetry Explorer
(IXPE). IXPE monitored the source in three different Epochs, sampling two
Main-on and one Short-on state of the well-known super-orbital period of the
source. We find that the 2-7 keV polarization fraction increases significantly
from ~ $7-9$ % in the Main-on state to ~ $15-19$ % in the Short-on state, while
the polarization angle remains more or less constant or changes slightly, ~
$47-59$ degrees, in all three Epochs. The polarization degree and polarization
angle are consistent with being energy-independent for all three Epochs. We
propose that in the Short-on state, when the neutron star is partially blocked
by the disk warp, the increase in the polarization fraction can be explained as
a result of the preferential obstruction of one of the magnetic poles of the
neutron star.
