High resolution ALMA and HST imaging of $\kappa$CrB: a broad debris disc around a post-main sequence star with low-mass companions

Abstract

$\kappa$CrB is a $\sim 2.5$Gyr old K1 sub-giant star, with an eccentric exo-Jupiter at $\sim 2.8$au and a debris disc at tens of au. We present ALMA Band 6 ($1.3$mm) and HST scattered light ($0.6\mu$m) images, demonstrating $\kappa$CrB's broad debris disc, covering an extent $50-180$au in the millimetre (peaking at $110$au), and $51-280$au in scattered light (peaking at $73$au). By modelling the millimetre emission, we estimate the dust mass as $\sim 0.016M\oplus$, and constrain lower-limit planetesimal sizes as $D_{\max }>1$km and the planetesimal belt mass as $M_{\mathrm{disc}}>1M_{\oplus }$. We constrain the properties of an outer body causing a linear trend in 17 years of radial velocity data to have a semi-major axis $8-66$au and a mass $(0.4-120)M_{\mathrm{Jup}}$. There is a large inner cavity seen in the millimetre emission, which we show is consistent with carving by such an outer massive companion with a string of lower mass planets. Our scattered light modelling shows that the dust must have a high anisotropic scattering factor ($g\sim 0.8-0.9$) but an inclination ($i\sim 30-40$degrees) that is inferred to be significantly lower than the $i\sim 61$degrees millimetre inclination. The origin of such a discrepancy is unclear, but could be caused by a misalignment in the micron and millimetre sized dust. We place an upper limit on the CO gas mass of $M_{\mathrm{CO}}<(4.2-13)\times 10^{-7}{M}_{\oplus }$, and show this to be consistent with levels expected from planetesimal collisions, or from CO-ice sublimation as $\kappa$CrB begins its giant branch ascent.

Accepted for publication in MNRAS. 21 pages, 14 figures

References in corpus (34)

• Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
• A Steeper than Linear Disk Mass-Stellar Mass Scaling Relation
• The frequency of planetary debris around young white dwarfs
• Debris Disk Evolution Around A Stars
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• Molecular Gas Clumps from the Destruction of Icy Bodies in the $\beta$ Pictoris Debris Disk
• HST/ACS Multiband Coronagraphic Imaging of the Debris Disk around Beta Pictoris
• Formation of planetary debris discs around white dwarfs I: Tidal disruption of an extremely eccentric asteroid
• The SCUBA-2 Cosmology Legacy Survey: ALMA resolves the bright-end of the sub-millimeter number counts
• Detection of exocometary CO within the 440 Myr-old Fomalhaut belt: a similar CO+CO${}_2$ ice abundance in exocomets and Solar System comets
• Near-infrared scattered light properties of the HR4796A dust ring: a measured scattering phase function from 13.6deg to 166.6deg
• Debris from giant impacts between planetary embryos at large orbital radii
• Do Two Temperature Debris Disks Have Multiple Belts?
• SONS: The JCMT legacy survey of debris discs in the submillimetre
• Exocometary gas structure, origin and physical properties around $\beta$ Pictoris through ALMA CO multi-transition observations
• The History of the Solar System's Debris Disc: Observable Properties of the Kuiper Belt
• Kuiper Belt-Like Hot and Cold Populations of Planetesimal Inclinations in the $\beta$ Pictoris Belt Revealed by ALMA
• Retired A Stars and Their Companions II: Jovian planets orbiting kappa Coronae Borealis and HD167042
• Collisional dust avalanches in debris discs
• Revealing Asymmetries in the HD 181327 Debris Disk: A Recent Massive Collision or ISM Warping
• Does the presence of planets affect the frequency and properties of extrasolar Kuiper Belts? Results from the Herschel DEBRIS and DUNES surveys
• CO mass upper limits in the Fomalhaut ring - the importance of NLTE excitation in debris discs and future prospects with ALMA
• Solution to the debris disc mass problem: planetesimals are born small?
• The Mass of Stirring Bodies in the AU Mic Debris Disk Inferred from Resolved Vertical Structure
• Population synthesis of exocometary gas around A stars
• On the observability of resonant structures in planetesimal disks due to planetary migration
• A statistically significant lack of debris discs in medium separation binary systems
• The unseen planets of double belt debris disk systems
• High resolution ALMA and HST images of q${}^1$ Eri: an asymmetric debris disc with an eccentric Jupiter
• No significant correlation between radial velocity planet presence and debris disc properties
• Planetary Migration to Large Radii
• Eccentric debris disc morphologies I: exploring the origin of apocentre and pericentre glows in face-on debris discs
• A multi-wavelength study of the debris disc around 49 Cet
• Twisted debris: how differential secular perturbations shape debris disks

Cited by in corpus (7)

• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) V: Comparison between scattered light and thermal emission
• Eccentric debris disc morphologies II: Surface brightness variations from overlapping orbits in narrow eccentric discs
• ALMA Reveals an Eccentricity Gradient in the Fomalhaut Debris Disk
• ALMA and Keck analysis of Fomalhaut field sources: JWST's Great Dust Cloud is a background object
• Scattered polarized radiation of extrasolar circumplanetary rings
• Planetesimals drifting through dusty and gaseous white dwarf debris discs: Types I, II and III-like migration
• Study of the migration of Earth-like planets in planetesimal disks and the formation of debris disks