Morphology of the gas-rich debris disk around HD 121617 with SPHERE observations in polarized light^★

¹ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
e-mail: clement.perrot@obspm.fr
² Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile
³ Núcleo Milenio Formación Planetaria – NPF, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile
⁴ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁵ Escuela de Ciencias, Universidad Viña del Mar, Viña del Mar, Chile
⁶ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁷ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁸ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁹ School of Physics and Astronomy, Sir William Henry Bragg Building, University of Leeds, Leeds LS2 9JT, UK
¹⁰ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 8320000, Chile
¹¹ School of Physics and Astronomy, Monash University, Vic 3800, Australia
¹² Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

Received: 5 August 2022
Accepted: 6 February 2023

Abstract

Context. Debris disks are the signposts of collisionally eroding planetesimal circumstellar belts, whose study can put important constraints on the structure of extrasolar planetary systems. The best constraints on the morphology of such disks are often obtained from spatially resolved observations in scattered light. In this paper, we investigate the young (~16 Myr) bright gas-rich debris disk around HD 121617.

Aims. We use new scattered light observations from VLT/SPHERE to characterize the morphology and the dust properties of the debris disk. From these properties, we can then derive constraints on the physical and dynamical environment of this system, for which significant amounts of gas have been detected.

Methods. The disk morphology is constrained by linear polarimetric observations in the J band. Based on our modeling results and archival photometry, we also model the spectral energy distribution (SED) to put constraints on the total dust mass and dust size distribution. Finally, we explore different scenarios that could explain these new constraints.

Results. We present the first resolved image in scattered light of the debris disk around HD 121617. We fit the morphology of the disk, finding a semi-major axis of 78.3 ± 0.2 au, an inclination of 43.1 ± 0.2°, and a position angle of the major axis with respect to north of 239.8 ± 0.3°, which is compatible with the previous continuum and CO detection with ALMA. Our analysis shows that the disk has a very sharp inner edge, possibly sculpted by a yet-undetected planet or gas drag. While less sharp, its outer edge is steeper than expected for an unperturbed disk, which could also be due to a planet or gas drag, but future observations probing the system farther from the main belt would help explore this possibility further. The SED analysis leads to a dust mass of 0.21 ± 0.02 M_⊕ and a minimum grain size of 0.87 ± 0.12 μm, smaller than the blowout size by radiation pressure, which is not unexpected for very bright collisionally active disks.