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Peer-reviewedCC BY 4.0The Astrophysical Journal

Strong Polarization Signatures from Magnetically Stabilized Luminous Thin Accretion Disks

  • P. Chris Fragile1,2
  • Peter Anninos3
  • Madeline Breiling1
  • Derrick Pickrel3,4
  • Gabrielle Ruminski5
5 affiliations
  1. 1College of Charleston
  2. 2Flatiron Institute
  3. 3Lawrence Livermore National Laboratory
  4. 4University of California
  5. 5St. Paul’s School
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Abstract

We utilize the Monte Carlo radiation transport capabilities of Cosmos++ to explore the polarization and Faraday rotation of radiation emitted from a set of general relativistic radiation magnetohydrodynamic simulations of magnetically stabilized, thin, black hole accretion disks. The guiding question is whether or not the Faraday rotation depolarizes the radiation to such a degree as to be inconsistent with the relatively high polarization measurements coming from the Imaging X-ray Polarimetry Explorer (IXPE). After first confirming that our code reproduces expected polarization results for electron clouds, planar scattering atmospheres, and active galactic nucleus disks, we demonstrate the polarization and Faraday rotation capabilities using a Novikov–Thorne disk threaded with a purely toroidal magnetic field. We then analyze temporal snapshots from three different simulations of luminous, thin accretion disks threaded with different magnetic field configurations. We find that the effects of Faraday rotation are generally modest over the energy range of interest, since the strongest fields present in these simulations (≳10 ⁸ G) are mostly hidden beneath the photosphere. We can easily produce polarization degrees ≥4% for sources seen mostly edge-on. As one example of a relevant target, we compare our results to an IXPE observation of Cygnus X-1, finding that we can match the polarization degree quite well, though our polarization angle is rotated approximately 90 ∘ with respect to the observed data. We speculate on a few possible explanations for this.

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Cite

BibTeXRIS
BibTeX
@article{fragile2026strong,
  title = {{Strong Polarization Signatures from Magnetically Stabilized Luminous Thin Accretion Disks}},
  author = {P. Chris Fragile and Peter Anninos and Madeline Breiling and Derrick Pickrel and Gabrielle Ruminski},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/aea836},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea836},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Strong Polarization Signatures from Magnetically Stabilized Luminous Thin Accretion Disks
AU  - P. Chris Fragile
AU  - Peter Anninos
AU  - Madeline Breiling
AU  - Derrick Pickrel
AU  - Gabrielle Ruminski
PY  - 2026
DA  - 2026/10/16
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea836
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea836
AB  - We utilize the Monte Carlo radiation transport capabilities of Cosmos++ to explore the polarization and Faraday rotation of radiation emitted from a set of general relativistic radiation magnetohydrodynamic simulations of magnetically stabilized, thin, black hole accretion disks. The guiding question is whether or not the Faraday rotation depolarizes the radiation to such a degree as to be inconsistent with the relatively high polarization measurements coming from the Imaging X-ray Polarimetry Explorer (IXPE). After first confirming that our code reproduces expected polarization results for electron clouds, planar scattering atmospheres, and active galactic nucleus disks, we demonstrate the polarization and Faraday rotation capabilities using a Novikov–Thorne disk threaded with a purely toroidal magnetic field. We then analyze temporal snapshots from three different simulations of luminous, thin accretion disks threaded with different magnetic field configurations. We find that the effects of Faraday rotation are generally modest over the energy range of interest, since the strongest fields present in these simulations (≳10 ⁸ G) are mostly hidden beneath the photosphere. We can easily produce polarization degrees ≥4% for sources seen mostly edge-on. As one example of a relevant target, we compare our results to an IXPE observation of Cygnus X-1, finding that we can match the polarization degree quite well, though our polarization angle is rotated approximately 90 ∘ with respect to the observed data. We speculate on a few possible explanations for this.
SN  - 0004-637X
SN  - 1538-4357
ER  -