The outer edges of the discs around HD 206893 and HR 8799 are smooth, which the paper reads as scattered discs, as both stars have massive inner companions.

The paper

The paper's details are OpenAlex's; the citation count is OpenAlex's, 15 Oct 2026. The line on the paper is machine-written, as noted under Why it matters.

Why it matters

Written by Claude (claude-sonnet-5-5) on 15 Oct 2026 from the paper's abstract (as arXiv publishes it) and its OpenAlex record. Machine-written context to help a reader: it is not evidence, it moves no number, and it may be wrong. The quoted sentence is the claim; where it stands is computed from the record. If it misreads the paper, tell the stewards.

The story so far

1. 1

   What the authors did

   The author derived a model for the disc's outer edge, assuming a Rayleigh distribution of eccentricities, and fitted it to ALMA observations of five wide debris discs: HD 107146, HD 92945, HD 206893, AU Mic and HR 8799.

   Machine-written from the paper's abstract, as noted under Why it matters.

2. 2

   What they found

   • The sharper a disc's outer edge, the lower the eccentricity dispersion of its planetesimals must be, and the edge can be described with a tanh profile.
   • HD 107146, HD 92945 and AU Mic have the sharpest outer edges, with e_rms of about 0.10 to 0.15 if self-stirred, suggesting Pluto-sized objects embedded in the disc.
   • HD 206893 and HR 8799 have smooth outer edges, indicative of scattered discs since both have massive inner companions.

   Machine-written from the paper's abstract, as noted under Why it matters.

3. 3

   What has been checked on Ecdysis

   Exuvia registered the claim on 15 October 2026, with a test written from the paper. No check has been filed yet.

What would check it

How far it has been checked

1. 1
   Same data, same methodverification · not yet

   Not yet: re-run the paper's analysis on its own data, where the authors have published it.

2. 2
   New data, same methodreproduction · not yet

   Not yet: the same method on new data covering the claim's population and period. Established needs one.

3. 3
   The designrobustness tests and arguments · not yet

   Nothing yet: change the method or the data and see whether it holds (a robustness test), or argue that the method does not test what the claim says.

How sure is the record?

Share this finding

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Click a post's text to select all of it. Both posts give the claim's standing on the record, and the longer one says what the checks show and what they do not; the wording changes when the record does. The longer post quotes the paper first, then gives the machine-written headline, marked as such; edit it as you like. To cite the claim, see Cite this claim.

What would prove it wrong

Refuted if high‑resolution imaging (e.g., ALMA) of HD 206893 or HR 8799 shows an outer edge that is sharply truncated rather than smoothly declining, i.e., a drop in surface density within <10% of the disc radius.

The test as Exuvia registered it on 15 Oct 2026, written from the paper's words.

The wider literature

Other claims from the same paper

• uncheckedThe paper relates a disc's orbital eccentricity spread to its outer-edge smoothness, with a different factor if self-stirring has spread the semi-major axes.“If the semi-major axis distribution has sharp edges $e_\mathrm{rms}$ is roughly $1.2 l_{\rm out}/r_{\max}$, or $e_\mathrm{rms}=0.77 l_{\rm out}/r_{\max}$ if semi-major axes have diffused due to self-…”

Headlines are machine-written from the paper's abstract, or from the quote and the paper's title where no abstract is open; each claim's own words are quoted beneath its headline.