Pith Number

pith:WU4RYKGG

pith:2026:WU4RYKGG7M4U6RVZ7KIFQILCNF

not attested not anchored not stored refs resolved

The NuSTAR view of Ultra-Compact X-ray Binaries

A. Borghese, M. Armas Padilla, T. Mu\~noz-Darias

Ultra-compact X-ray binaries exhibit spectral properties similar to longer-period low-mass X-ray binaries, indicating comparable conditions in their innermost accretion regions.

arxiv:2604.13187 v1 · 2026-04-14 · astro-ph.HE

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\usepackage{pith}
\pithnumber{WU4RYKGG7M4U6RVZ7KIFQILCNF}

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Record completeness

1 Bitcoin timestamp

2 Internet Archive

3 Author claim open · sign in to claim

4 Citations open

5 Replications open

✓ Portable graph bundle live · download bundle · merged state

The bundle contains the canonical record plus signed events. A mirror can host it anywhere and recompute the same current state with the deterministic merge algorithm.

Claims

C1strongest claim

UCXBs exhibit similar spectral properties to their longer-period counterparts, suggesting no major differences in the innermost regions of X-ray binaries, regardless of disc size or chemical composition. A possible exception is found in the soft-state sample, which shows Comptonisation fractions higher than those typically observed in regular LMXBs.

C2weakest assumption

That the three-component model is the appropriate description for UCXB spectra and that the 11-source archival sample adequately represents the full range of UCXB behavior and states.

C3one line summary

Ultra-compact X-ray binaries exhibit similar hard X-ray spectral properties to standard low-mass X-ray binaries, including typical continuum values per state, with higher Comptonisation fractions in soft states and a very cold hard state discovered in 4U 1626-67.

References

2 extracted · 2 resolved · 0 Pith anchors

[1] F., Margon, B., Deutsch, E 1997

[2] B.3:Left:Spectrum of IGR J16597−3704.Right:Spectrum of 4U 1916−053 1916

Receipt and verification

First computed	2026-06-03T14:05:24.551736Z
Builder	pith-number-builder-2026-05-17-v1
Signature	Pith Ed25519 (`pith-v1-2026-05`) · public key
Schema	pith-number/v1.0

Canonical hash

b5391c28c6fb394f46b9fa905821626974db85c80fb84746e0b76a13d93b04cf

Aliases

arxiv: 2604.13187 · arxiv_version: 2604.13187v1 · doi: 10.48550/arxiv.2604.13187 · pith_short_12: WU4RYKGG7M4U · pith_short_16: WU4RYKGG7M4U6RVZ · pith_short_8: WU4RYKGG

Agent API

Resolver JSON Graph JSON Events JSON Schema Signing key

Verify this Pith Number yourself

curl -sH 'Accept: application/ld+json' https://pith.science/pith/WU4RYKGG7M4U6RVZ7KIFQILCNF \
  | jq -c '.canonical_record' \
  | python3 -c "import sys,json,hashlib; b=json.dumps(json.loads(sys.stdin.read()), sort_keys=True, separators=(',',':'), ensure_ascii=False).encode(); print(hashlib.sha256(b).hexdigest())"
# expect: b5391c28c6fb394f46b9fa905821626974db85c80fb84746e0b76a13d93b04cf

Canonical record JSON

{
  "metadata": {
    "abstract_canon_sha256": "772d73c05225abec210d22449e9e7ed20d948bdc73ca0b819e21b2cc8bf7c680",
    "cross_cats_sorted": [],
    "license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
    "primary_cat": "astro-ph.HE",
    "submitted_at": "2026-04-14T18:10:26Z",
    "title_canon_sha256": "189c04d51035d5fc7c2f586a161080c36fddb5d00bb81626639ba87bde4f6d29"
  },
  "schema_version": "1.0",
  "source": {
    "id": "2604.13187",
    "kind": "arxiv",
    "version": 1
  }
}