A close-in giant planetary (CGP) system has a net polarization signal whose
value varies depending on the orbital phase of the planet. This polarization
signal is either caused by the stellar occultation or by reflected starlight
from the surface of the orbiting planet. When the CGP system is located in the
Galactic bulge, its polarization signal becomes too weak to be measured
directly. One method for detecting and characterizing these weak polarization
signatures due to distant CGP systems is gravitational microlensing. In this
work, we focus on potential polarimetric observations of highly-magnified
microlensing events of CGP systems. When the lens is passing directly in front
of the source star with its planetary companion, the polarimetric signature
caused by the transiting planet is magnified. As a result some distinct
features in the polarimetry and light curves are produced. In the same way
microlensing amplifies the reflection-induced polarization signal. While the
planet-induced perturbations are magnified, whenever these polarimetric or
photometric deviations vanish for a moment the corresponding magnification
factor or the polarization component(s) is equal to the related one due to the
planet itself. In order to evaluate the observability of such systems through
polarimetric or photometric observations of high-magnification microlensing
events, we simulate these events by considering confirmed CGP systems as their
source stars and conclude that the efficiency for detecting the planet-induced
signal with the state-of-the-art polarimetric instrument (FORS2/VLT) is less
than 0.1 %. Consequently, these planet-induced polarimetry perturbations can
likely be detected under favorable conditions by high-resolution and
short-cadence polarimeters of the next generation.Comment: 9 pages, 7 figures, one tabl
