  X-ray polarimetry has great scientific potential and new experiments, such as
X-Calibur, PoGOLite, XIPE, and GEMS, will not only be orders of magnitude more
sensitive than previous missions, but also provide the capability to measure
polarization over a wide energy range. However, the measured spectra depend on
the collection area, detector responses, and, in case of balloon-borne
experiments, the absorption of X-rays in the atmosphere, all of which are
energy dependent. Combined with the typically steep source spectra, this leads
to significant biases that need to be taken into account to correctly
reconstruct energy-resolved polarization properties. In this paper, we present
a method based on an iterative unfolding algorithm that makes it possible to
simultaneously reconstruct the energy spectrum and the polarization properties
as a function of true photon energy. We apply the method to a simulated
X-Calibur data set and show that it is able to recover both the energy spectrum
and the energy-dependent polarization fraction.
