High-resolution ALMA and HST imaging of κCrB: a broad debris disc around a post-main-sequence star with low-mass companions
- Author(s)
- J. B. Lovell, M. C. Wyatt, P. Kalas, G. M. Kennedy, S. Marino, A Bonsor, Z Penoyre, B J Fulton, Nicole Pawellek
- Abstract
κ CrB 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 (0.6 μm) images, demonstrating κ 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 ∼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 κ CrB begins its giant branch ascent.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Eötvös Loránd Research Network, University of Cambridge, University of California, Berkeley, University of Warwick, California Institute of Technology (Caltech)
- Journal
- Monthly Notices of the Royal Astronomical Society
- Volume
- 517
- Pages
- 2546-2566
- No. of pages
- 21
- ISSN
- 0035-8711
- DOI
- https://doi.org/10.1093/mnras/stac2782
- Publication date
- 12-2022
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103003 Astronomy, 103004 Astrophysics
- Keywords
- ASJC Scopus subject areas
- Astronomy and Astrophysics, Space and Planetary Science
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/highresolution-alma-and-hst-imaging-of-crb-a-broad-debris-disc-around-a-postmainsequence-star-with-lowmass-companions(387d24ef-3621-4cc2-900e-223f62ccca11).html