- Names
-
- M. Bonduelle
- M. Bonduelle
- J. Milli
- O. Poch
- N. Engler
- M. Rigouleau
- R. Tazaki
- J. Ma
- J. Olofsson
- J.-B.. Renard
- J. Lasue
- R. Sultana
- G. Duchêne
- L. Martinien
- M. Roumesy
- C.H. Chen
- C. Lisse
- J.-C. Augereau
- Title
- The dust in Sauro's eye Observational and experimental results on the debris disk around HR 4796
- Abstract
- Context. The debris disk surrounding HR4796 is a bright, narrow ring, that has been observed at multiple wavelengths, both in scattered light and thermal emission. The optical properties of the dust particles (scattering phase function -SPF; degree of linear polarization -DoLP, reflectance), that can be retrieved through scattered light imaging, are linked to the physico-chemical properties of the dust particles (size, shape, composition...), but this is a complex problem. HR4796 in particular presents several peculiarities, especially an unusually high DoLP at small scattering angles. Aims. We aim at better constraining the physico-chemical properties of the dust particles orbiting in the disk. Methods.We use multi-wavelengths scattered light observations of HR4796, obtained with SPHERE/IRDIS and SPHERE/ZIMPOL. We forward-model those observations using a novel joint parametric approach to constrain the morphology, the scattering phase function, and the degree of linear polarization of the disk. These observations are then compared to laboratory measurements, previous observations of HR4796 and of some Solar system asteroids and comets. Results. We present new observational data in scattered light of HR4796, for = 0.63 µm, = 0.79 µm, and = 1.25 µm. We modelled the disk at each of these wavelengths, and found geometric parameters consistent with previous results. We obtained the parametrized SPF and DoLP over the whole range of scattering angles (13° to 167°), and extracted the DoLP at 90° (without any parametrization) as well as the spectral reflectance from visible to near-infrared wavelength range. We compare the reflectance and polarimetric properties of HR 4796 to those measured on a laboratory dust sample and obtained from previous results on HR4796. We find that the sample providing the best match to these properties appears to be large (from a few micrometers to 100 µm) iron sulfides particles, such as pyrrhotite and troilite. Such iron sulfides are among the opaque minerals (FexSy, FeNi, etc.) that contribute to the low albedo of some Solar system small bodies (B/C/D/P-type asteroids, comets etc.). Conclusions. We confirm that the DoLP of HR4796 peaks at high values (> 45%) and for small scattering angles (< 55°). We observe a red spectral slope in the visible and near-infrared wavelength range, as well as a blue polarimetric slope. These results are compatible with large (a few micrometers to 100 µm) opaque minerals being the main scatterers in the disk. We show that the DoLP of HR4796 is notably di erent from that of Solar system comets and seems closer to that of some processed near-Earth orbit asteroids, possibly indicating devolatilization/melting induced by space weathering on the dust particles of HR4796.
- Keywords
- reflectance, polarization
- Content
- astrophysics, spectral data use
- Year
- 2026
- Journal
- Astronomy and Astrophysics
- Document type
- article
- Publication state
- in press