  Context: Variations in the mass accretion rate appear to be responsible for
the rapid transitions in spectral type that are observed in increasingly more
active galactic nuclei (AGNs). These objects are now labeled "changing-look"
AGNs and are key objects for understanding the physics of accretion onto
supermassive black holes. Aims: We aim to complement the analysis and
interpretation of changing-look AGNs by modeling the polarization variations
that can be observed, in particular, polarized-light echoes. Methods: We built
a complex and representative model of an AGN and its host galaxy and ran
radiative transfer simulations to obtain realistic time-dependent polarization
signatures of changing-look objects. Based on actual data, we allowed the
system to become several times fainter or brighter within a few years, assuming
a rapid change in accretion rate. Results: We obtain time-dependent
polarization signatures of distant high-luminosity (quasars) and nearby
low-luminosity (Seyferts) changing-look AGNs for a representative set of
inclinations. We predict the evolution of the continuum polarization for future
polarimetric campaigns with the goal to better understand the physics at work
in these objects. We also investigate highly inclined AGNs that experience
strong accretion rate variations without appearing to change state. We apply
our modeling to Mrk 1018, the best-documented case of a changing-look AGN, and
predict a variation in its polarization after the recent dimming of its
continuum.
