Characterization of debris disks observed with SPHERE

¹ ETH Zurich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
² CNRS, IPAG, Université Grenoble Alpes, IPAG, 38000 Grenoble, France
³ Institut für Astrophysik Universität Wien, Türkenschanzstraße 17, 1180 Vienna, Austria
⁴ IKonkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
⁵ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
⁷ European Southern Observatory, Karl Schwarzschild St, 2, 85748 Garching, Germany
⁸ Leiden Observatory, University of Leiden, Einsteinweg 55, 2333CA Leiden, The Netherlands
⁹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁰ Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden
¹¹ Johns Hopkins University, Baltimore, MD, USA
¹² Aix Marseille Université, CNRS, LAM – Laboratoire d’Astrophysique de Marseille, UMR 7326, 13388 Marseille, France
¹³ Anton Pannekoek Astronomical Institute, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
¹⁴ University of Galway, University Road H91 TK33 Galway, Ireland
¹⁵ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
¹⁶ Millennium Nucleus on Young Exoplanets and their Moons (YEMS), Chile
¹⁷ DOTA, ONERA, Université Paris Saclay, 91123 Palaiseau, France
¹⁸ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁹ Kiepenheuer-Institut für Sonnenphysik, Schneckstr. 6, 79104 Freiburg, Germany
²⁰ European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago, Chile
²¹ Centre de Recherche Astrophysique de Lyon, CNRS/ENSL Université Lyon 1, 9 av. Ch. André, 69561 Saint-Genis-Laval, France
²² Center for Astrophysics and Planetary Science, Department of Astronomy, Cornell University, Ithaca, NY 14853, USA

^★ Corresponding author: englern@ethz.ch

Received: 1 April 2025
Accepted: 9 October 2025

Abstract

Aims. This study aims to characterize debris disk targets observed with SPHERE across multiple programs, with the goal of identifying systematic trends in disk morphology, dust mass, and grain properties as a function of stellar parameters. By combining scattered-light imaging with photometric and parametric modeling, we seek to improve our understanding of the composition and evolution of circumstellar material in young debris systems and to place debris disks in the broader context of planetary system architectures.

Methods. We analyzed a sample of 161 young main-sequence stars using archival SPHERE observations at optical and near-infrared (IR) wavelengths. Disk geometries were derived from ellipse fitting and model grids, while dust mass and properties were constrained by modified blackbody (MBB) and size distribution (SD) modeling of spectral energy distributions (SEDs). We also carried out dynamical modeling to assess whether the observed disk structures can be explained by the presence of unseen planets.

Results. We resolve 51 debris disks, including four new detections where disks are resolved for the first time: HD 36968, BD-20 951, and the inner belts of HR 8799 and HD 36546. In addition, we find a second transiting giant planet in the HD 114082 system, with a radius of 1.29 ± 0.05 R_Jup and an orbital distance of ~1 au, providing an important new benchmark for planet–disk interaction studies. Beyond these new detections, we identify nine multi-belt systems, with outer-to-inner belt radius ratios of 1.5–2, and find close agreement between scattered-light and millimeter continuum belt radii with a mean ratio R_belt(near-IR)/R_belt(mm) of 1.05 ± 0.04. Belt radii scale weakly with stellar luminosity (R_belt ∝ L_⋆^0.11±0.05), but show steeper dependencies when separated by CO and CO₂ freeze-out regimes, and also increase with age as R_belt ∝ t_age^0.37±0.11. Uniform image modeling yields vertical disk aspect ratios of 0.02–0.06, consistent with collisionally stirred belts, while gas-rich systems show unusually small values. Inner density slopes steepen with stellar luminosity, indicating more efficient dust removal around luminous stars. Disk fractional luminosities follow collisional decay trends, declining as t_age^{−1.18±0.14} for A-type and t_age^{−0.81±0.12} for F-type stars. SD modeling yields minimum grain sizes consistently above the blowout limit, typically >0.8 μm, with a mean SD index of q = 3.6, assuming astrosilicate composition. The inferred dust masses span 10⁻⁵−1 M_⊕ from MBB modeling (and 0.01–1 M_⊕ from SD modeling for detected disks). These masses scale as R_beltⁿ with n > 2 in belt radius and super-linearly with stellar mass, consistent with trends seen in protoplanetary disks (PPDs). Our detailed analysis of disk scattered-light non-detections indicates that they are mainly caused by low dust masses, unfavorable viewing geometries, or suboptimal observing conditions. SD modeling combined with Mie theory further shows that bulk albedos are consistently above 0.5 with little variation, making albedo differences an unlikely explanation. To explore this further, we introduced a new parametric approach based on scattered-light and polarized-light images, which provides independent estimates of dust albedo and maximum polarization fraction. We find a correlation between measured disk polarized flux and IR excess, with a slope shallower than that of optical total-intensity fluxes measured with HST/STIS. The offset of ~1 dex between total-intensity and polarized fluxes arises because polarized flux represents only a fraction of the total scattered light which depends on both grain properties and disk inclination. Finally, a comparison of planetary architectures shows that most benchmark systems resemble the Solar System, with multiple planets located inside wide Kuiper-belt analogues. Dynamical modeling further indicates that many observed gaps and inner edges can be explained by unseen planets below current detection thresholds, typically with Neptune- to sub-Jovian masses, underscoring the likely ubiquity of such planets in shaping debris disk morphologies.