SPHERE/ZIMPOL insights into discs around evolved stars: arcs, asymmetries and dust properties
arXiv:2503.23646 · doi:10.1017/pasa.2025.10079
Abstract
Second-generation circumbinary discs around evolved binary stars, such as post-Asymptotic Giant Branch (post-AGB) binaries, provide insights into poorly understood mechanisms of dust processing and disc evolution across diverse stellar environments. We present a multi-wavelength polarimetric survey of five evolved binary systems - AR Pup, HR 4049, HR 4226, U Mon, and V709 Car - using the Very Large Telescope SPHERE/ZIMPOL instrument. Post-AGB discs show significant polarimetric brightness at optical and near-IR wavelengths, often exceeding 1% of the system's total intensity. We also measured a maximum fractional polarisation of the scattered light for AR Pup of ~0.7 in the V-band and ~0.55 in the I-band. To investigate wavelength-dependent polarisation, we combine the SPHERE/ZIMPOL dataset with results from previous SPHERE/IRDIS studies. This analysis reveals that post-AGB discs exhibit a grey to blue polarimetric colour in the optical and near-IR. Along with high fractional polarisation of the scattered light and polarised intensity distribution, these findings are consistent with a surface dust composition dominated by porous aggregates, reinforcing independent observational evidence for such grains in post-AGB circumbinary discs. We also find evidence of diverse disc geometries within the post-AGB sample, including arcs, asymmetries and significant variations in disc size across optical and near-IR wavelengths for some systems (U Mon, V709 Car). On comparing post-AGB discs to circumstellar environments around AGB stars and YSOs, we found that post-AGB systems exhibit a higher degree of polarisation than single AGB stars and are comparable to the brightest protoplanetary discs around YSOs.
36 pages, 23 figures, accepted to PASA
References in corpus (30)
- Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
- Keplerian discs around post-AGB stars: a common phenomenon?
- Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Late infall causing disk misalignment and dynamic structures in SU Aur
- Optically visible post-AGB/RGB stars and young stellar objects in the Small Magellanic Cloud: candidate selection, spectral energy distributions and spectroscopic examination
- Disks Around T Tauri Stars with SPHERE (DARTTS-S) II: Twenty-one new polarimetric images of young stellar disks
- SPITZER survey of dust grain processing in stable discs around binary post-AGB stars
- Establishing binarity amongst Galactic RV Tauri stars with a disc
- Effect of dust size and structure on scattered light images of protoplanetary discs
- A population of transition disks around evolved stars: Fingerprints of planets? Catalog of disks surrounding Galactic post-AGB binaries
- Defining the instability strip of pulsating post-AGB binary stars from ASAS and NSVS photometry
- Detection of Keplerian dynamics in a disk around the post-AGB star AC Her
- How large are the monomers of dust aggregates in planet-forming disks?: Insights from quantitative optical and near-infrared polarimetry
- A mid-IR interferometric survey with MIDI/VLTI: resolving the second-generation protoplanetary disks around post-AGB binaries
- Fractal aggregates of sub-micron-sized grains in the young planet-forming disk around IM Lup
- A second post-AGB nebula that contains gas in rotation and in expansion: ALMA maps of IW Car
- Effect of dust grain porosity on the appearance of protoplanetary disks
- The evolved circumbinary disk of AC Her: a radiative transfer, interferometric and mineralogical study
- Keplerian disks and outflows in post-AGB stars: AC Herculis, 89 Herculis, IRAS 19125+0343, and R Scuti
- Observed polarized scattered light phase functions of planet-forming disks
- Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon
- Quantitative polarimetry of the disk around HD 169142
- Interstellar Polarization Survey II: General Interstellar Medium
- Resolved imaging of the AR Puppis circumbinary disk
- Physical properties of galactic RV Tauri stars from Gaia DR2 data
- Transition disc nature of post-AGB binary systems confirmed by mid-infrared interferometry
- What does a typical full-disc around a post-AGB binary look like? -- Radiative transfer models reproducing PIONIER, GRAVITY, and MATISSE data
- Quantitative polarimetry for the transition disk in RX J1604.3-213010
- Second-generation protoplanetary discs around evolved binaries: a high-resolution polarimetric view with SPHERE/IRDIS
- Color measurements of the polarized light scattered by the dust in protoplanetary disks
- Multiwavelength high-resolution polarimetric imaging of second-generation disc around post-AGB binary IRAS 08544-4431 with SPHERE