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We obtained polarimetric differential imaging of a gas-rich debris diskaround HD 141569A with SPHERE in the H-band to compare the scatteringproperties of the innermost ring at 44 au with former observations in totalintensity with the same instrument. In polarimetric imaging, we observed thatthe intensity of the ring peaks in the south-east, mostly in the forwarddirection, whereas in total intensity imaging, the ring is detected only at thesouth. This noticeable characteristic suggests a non-uniform dust density inthe ring. We implemented a density function varying azimuthally along the ringand generated synthetic images both in polarimetry and in total intensity,which are then compared to the actual data. We find that the dust density peaksin the south-west at an azimuthal angle of $220^{\circ} \sim 238^{\circ}$ witha rather broad width of $61^{\circ} \sim 127^{\circ}$. Although there are stilluncertainties that remain in the determination of the anisotropic scatteringfactor, the implementation of an azimuthal density variation to fit the dataproved to be robust. Upon elaborating on the origin of this dust densitydistribution, we conclude that it could be the result of a massive collisionwhen we account for the effect of the high gas mass that is present in thesystem on the dynamics of grains. Using the outcome of this modelization, wefurther measured the polarized scattering phase function for the observedscattering angle between 33$^{\circ}$ and 147$^{\circ}$ as well as the spectralreflectance of the southern part of the ring between 0.98 $\mu$m and 2.1$\mu$m. We tentatively derived the grain properties by comparing thesequantities with MCFOST models and assuming Mie scattering. Our preliminaryinterpretation indicates a mixture of porous sub-micron sized astro-silicateand carbonaceous grains.

Revealing asymmetrical dust distribution in the inner regions of HD 141569