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

Lovell, J. B. and Wyatt, M. C. and Kalas, P. and Kennedy, G. M. and Marino, S. and Bonsor, A. and Penoyre, Z. and Fulton, B. J. and Pawellek, N. (2022) High-resolution ALMA and HST imaging of κCrB: a broad debris disc around a post-main-sequence star with low-mass companions. Monthly Notices of the Royal Astronomical Society, 517 (2). pp. 2546-2566. ISSN 0035-8711. doi:10.1093/mnras/stac2782.

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κCrB is an ∼2.5 Gyr old K1 sub-giant star, with an eccentric exo-Jupiter at ∼2.8 au and a debris disc at tens of au. We present ALMA (Atacama Large Millimetre/submillimetre Array) Band 6 (1.3 mm) and Hubble Space Telescope scattered light (0.6μm) images, demonstrating κCrB’s broad debris disc, covering an extent 50−180au 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 ∼0.016 M_⊕⁠, and constrain lower-limit planetesimal sizes as D_(max) ≳ 1 km and the planetesimal belt mass as M_(disc) ≳ 1 M_⊕⁠. We constrain the properties of an outer body causing a linear trend in 17 yr of radial velocity data to have a semimajor axis 8–66 au and a mass 0.4−120 M_(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 ∼ 0.8–0.9) but an inclination (i ∼ 30°–40°) that is inferred to be significantly lower than the i ∼ 61° millimetre inclination. The origin of such a discrepancy is unclear, but could be caused by a misalignment in the micrometre- and millimetre-sized dust. We place an upper limit on the CO gas mass of M_(CO) < (4.2−13) × 10⁻⁷ M_⊕⁠, and show this to be consistent with levels expected from planetesimal collisions, or from CO-ice sublimation as κCrB begins its giant branch ascent.

Item Type:Article
Related URLs:
URLURL TypeDescription
Lovell, J. B.0000-0002-4248-5443
Wyatt, M. C.0000-0001-9064-5598
Kalas, P.0000-0002-6221-5360
Kennedy, G. M.0000-0001-6831-7547
Marino, S.0000-0002-5352-2924
Bonsor, A.0000-0002-8070-1901
Penoyre, Z.0000-0003-0244-4919
Fulton, B. J.0000-0003-3504-5316
Pawellek, N.0000-0002-9385-9820
Additional Information:We thank the anonymous referee for their insightful comments that greatly improved the clarity of this manuscript. We also thank Luca Matrà for providing code with which CO gas mass limit estimates were derived. We gratefully acknowledge the support and expertise provided by ALMA and HST staff involved in the data collection and post-processing/quality assurance undertaken in advance of our analysis. JBL is supported by an STFC postgraduate studentship. GMK is supported by the Royal Society as a Royal Society University Research Fellow. SM is supported by a Research Fellowship from Jesus College, Cambridge. AB is grateful to the Royal Society for a Dorothy Hodgkin Fellowship. PK thanks support from GO-13362 provided by NASA through a grant from STScI under NASA contract NAS5-26555. DATA AVAILABILITY. This work makes use of the following ALMA data: ADS/JAO.ALMA#2019.1.01443.T⁠. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The HST data used for this study are part of the Cycle 21 with proposal ID GO-13362 and are publicly available on the Barbara A. Mikulski Archive for Space Telescopes ( This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France. This research has made use of NASA’s Astrophysics Data System. All RV data used to model the planet fits have been included as a supporting file alongside this paper.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Jesus College, CambridgeUNSPECIFIED
Subject Keywords:stars: individual: HD 142091, infrared: planetary systems, submillimetre: planetary systems
Issue or Number:2
Record Number:CaltechAUTHORS:20221031-575177800.21
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117659
Deposited By: Research Services Depository
Deposited On:09 Nov 2022 20:10
Last Modified:11 Nov 2022 18:50

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