We present multi-epoch Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch observations of the protoplanetary disk around HD 135344B ( SAO 206462 ) .
The J -band scattered light imagery reveal , with high spatial resolution ( \sim 41 mas , 6.4 au ) , the disk surface beyond \sim 20 au .
Temporal variations are identified in the azimuthal brightness distributions of all epochs , presumably related to the asymmetrically shading dust distribution in the inner disk .
These shadows manifest themselves as narrow lanes , cast by localized density enhancements , and broader features which possibly trace the larger scale dynamics of the inner disk .
We acquired visible and near-infrared photometry which shows variations up to 10 % in the JHK bands , possibly correlated with the presence of the shadows .
Analysis of archival Very Large Telescope Interferometer/PIONIER H -band visibilities constrain the orientation of the inner disk to i = 18 \mbox { $ . \degr$ } 2 ^ { +3.4 } _ { -4.1 } and { PA } = 57 \mbox { $ . \degr$ } 3 \pm 5 \mbox { $ . \degr$ } 7 , consistent with an alignment with the outer disk or a minor disk warp of several degrees .
The latter scenario could explain the broad , quasi-stationary shadowing in N-NW direction in case the inclination of the outer disk is slightly larger .
The correlation between the shadowing and the near-infrared excess is quantified with a grid of radiative transfer models .
The variability of the scattered light contrast requires extended variations in the inner disk atmosphere ( H / r \lesssim 0.2 ) .
Possible mechanisms that may cause asymmetric variations in the optical depth ( \Delta \tau \lesssim 1 ) through the atmosphere of the inner disk include turbulent fluctuations , planetesimal collisions , or a dusty disk wind , possibly enhanced by a minor disk warp .
A fine temporal sampling is required to follow day-to-day changes of the shadow patterns which may be a face-on variant of the UX Orionis phenomenon .