  We present the first short time scale observations of the roAp star gamma Equ
in linear polarized light obtained with the PEPSI polarimeter installed at the
LBT. These observations are used to search for pulsation variability in Stokes
Q and U line profiles belonging to different elements. The atmospheres of roAp
stars are significantly stratified with spectral lines of different elements
probing different atmospheric depths. roAp stars with strong magnetic fields,
such as gamma Equ with a magnetic field modulus of 4kG and a pulsation period
of 12.21min, are of special interest because the effect of the magnetic field
on the structure of their atmospheres can be studied with greatest detail and
accuracy. Our results show that we may detect changes in the transversal field
component in Fe I and rare-earth lines possessing large second-order Lande
factors. Such variability can be due to the impact of pulsation on the
transverse magnetic field, causing changes in the obliquity angles of the
magnetic force lines. Further studies of roAp stars in linear polarized light
and subsequent detailed modelling are necessary to improve our understanding of
the involved physics.
