# Optical polarized phase function of the HR\,4796A dust ring

## TL;DR

This study measures the polarized phase function of dust in the HR4796A debris ring using high-contrast optical imaging, revealing irregular or aggregate particle properties that differ from simple spherical models.

## Contribution

First measurement of the polarized phase function of debris disk dust over a wide scattering angle range in optical wavelengths.

## Key findings

- Polarized phase function incompatible with compact spherical dust particles.
- Alternative dust models include irregular surface or aggregate particles.
- Provides new insights into dust grain properties in debris disks.

## Abstract

The scattering properties of the dust originating from debris discs are still poorly known. The analysis of scattered light is however a powerful remote-sensing tool to understand the physical properties of dust particles orbiting other stars. Scattered light is indeed widely used to characterise the properties of cometary dust in the solar system. We aim to measure the morphology and scattering properties of the dust from the debris ring around HR4796A in polarised optical light. We obtained high-contrast polarimetric images of HR4796A in the wavelength range 600-900nm with the SPHERE / ZIMPOL instrument on the Very Large Telescope. We measured for the first time the polarised phase function of the dust in a debris system over a wide range of scattering angles in the optical. We confirm that it is incompatible with dust particles being compact spheres under the assumption of the Mie theory, and propose alternative scenarios compatible with the observations, such as particles with irregular surface roughness or aggregate particles.