{
  "abstract": "Reflection off the companion star and its focused stellar wind is predicted to modulate the X-ray polarization of black hole X-ray binaries at half the orbital period ($P_{\\rm orb}/2$), with an energy-dependent amplitude. We test this prediction against all publicly available IXPE observations of Cygnus X-1, comprising 26 time bins of up to one day from 12 observation IDs spanning 2022-2024. Since the normalized Stokes parameters correlate linearly with the spectral hardness ratio in all three energy bands (2-4, 4-6, and 6-8 keV), we employ a simultaneous harmonic regression that decouples spectral variability from orbital modulation at both $P_{\\rm orb}/2$ and $P_{\\rm orb}$, complemented by direct fitting of 3D Monte Carlo radiative transfer stellar companion and wind-scattering templates. After removing the spectral hardness trend, neither approach reveals statistically significant orbital modulation: permutation tests yield $p > 0.01$ in all bands, with 99% confidence upper limits of 0.25%, 0.63%, and 1.96% on the $P_{\\rm orb}$ amplitude and 0.42%, 0.97%, and 2.78% on the $P_{\\rm orb}/2$ amplitude in the 2-4 keV, 4-6 keV, and 6-8 keV bands, respectively. The best-fit stellar companion and wind-scattering amplitude scaling factors in the three bands of $A = 0.67 \\pm 0.85$, $0.97 \\pm 0.62$, and $-1.06 \\pm 1.11$ are consistent with a null result. These non-detections are sensitivity-limited, as the predicted stellar companion and wind-scattering RMS amplitudes in the three bands of $\\approx$0.10%, $\\approx$0.33%, and $\\approx$0.49% lie below the statistical noise floor of $\\sim$0.18%, $\\sim$0.38%, and $\\sim$1.01%. We quantify the additional exposure required to detect the predicted signal and constrain the wind physics.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: ApJ 1010, 78 (2026)",
  "arxiv": "2606.30894",
  "author_total": 4,
  "authors": [
    {
      "name": "Sohee Chun"
    },
    {
      "name": "Bert Vander Meulen"
    },
    {
      "name": "Kun Hu"
    },
    {
      "name": "Henric Krawczynski"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8s3vkmb8pex96.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.30894",
  "fulltext_url": null,
  "id": "8s3vkmb8pex96",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.30894",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2606.30894",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-11",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8s3vkmb8pex96.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:52Z",
      "native_id": "2606.30894",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.30894"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Energy-Resolved Limits on Orbital X-ray Polarization Modulation in Cygnus X-1",
  "title_text": "Energy-Resolved Limits on Orbital X-ray Polarization Modulation in Cygnus X-1",
  "type": "preprint",
  "updated_at": "2026-10-30T12:33:41Z",
  "url": "https://research.draconitic.com/paper/8s3vkmb8pex96",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3847/1538-4357/aea617",
      "pid": "6bcjw19v068y5",
      "relation": "published-as",
      "title": "Energy-resolved Limits on Orbital X-Ray Polarization Modulation in Cygnus X-1",
      "venue": "The Astrophysical Journal"
    }
  ]
}