Dynamical Inference from Polarized Light Curves of Sagittarius A*
Polarimetric light curves of Sagittarius A* (Sgr A*) sometimes exhibit loops in the Stokes Q and U plane over time, often interpreted as orbiting hotspot motion. In this work, we apply the differential geometry of planar curves to develop a new technique for estimating polarimetric rotation rates. A...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/add729 |
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| author | Angelo Ricarte Nicholas S. Conroy Maciek Wielgus Daniel C. M. Palumbo Razieh Emami Chi-Kwan Chan |
| author_facet | Angelo Ricarte Nicholas S. Conroy Maciek Wielgus Daniel C. M. Palumbo Razieh Emami Chi-Kwan Chan |
| author_sort | Angelo Ricarte |
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| description | Polarimetric light curves of Sagittarius A* (Sgr A*) sometimes exhibit loops in the Stokes Q and U plane over time, often interpreted as orbiting hotspot motion. In this work, we apply the differential geometry of planar curves to develop a new technique for estimating polarimetric rotation rates. Applying this technique to 230 GHz light curves of Sgr A*, we find evidence of clockwise motion not only during a postflare period on 2017 April 11, as previously discovered, but also during the quiescent days imaged by the Event Horizon Telescope (EHT). The data exhibit a clockwise fraction of 0.65 ± 0.09 and an overall Q − U rotation rate of $-2.6\pm 0.6\,\deg \,{t}_{g}^{-1}$ . We analyze a library of general relativistic magnetohydrodynamic simulations and find that face-on, clockwise-rotating models with strong magnetic fields are most likely to be consistent with the observations. These results are consistent with EHT and GRAVITY Collaboration studies and indirectly support an interpretation in which the polarized image of Sgr A* has been rotated by an external Faraday screen. This technique offers a novel probe of event-horizon-scale dynamics that complements dynamical reconstructions. |
| format | Article |
| id | doaj-art-b9a14bfc80f74c679f23a7d7aeab737f |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-b9a14bfc80f74c679f23a7d7aeab737f2025-08-20T02:43:07ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01987215210.3847/1538-4357/add729Dynamical Inference from Polarized Light Curves of Sagittarius A*Angelo Ricarte0https://orcid.org/0000-0001-5287-0452Nicholas S. Conroy1https://orcid.org/0000-0003-2886-2377Maciek Wielgus2https://orcid.org/0000-0002-8635-4242Daniel C. M. Palumbo3https://orcid.org/0000-0002-7179-3816Razieh Emami4https://orcid.org/0000-0002-2791-5011Chi-Kwan Chan5https://orcid.org/0000-0001-6337-6126Black Hole Initiative at Harvard University , 20 Garden Street, Cambridge, MA 02138, USA ; angelo.ricarte@cfa.harvard.edu; Center for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USADepartment of Astronomy, University of Illinois at Urbana-Champaign , 1002 West Green Street, Urbana, IL 61801, USAInstituto de Astrofísica de Andalucía-CSIC , Glorieta de la Astronomía s/n, E-18008 Granada, SpainBlack Hole Initiative at Harvard University , 20 Garden Street, Cambridge, MA 02138, USA ; angelo.ricarte@cfa.harvard.edu; Center for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USACenter for Astrophysics | Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USASteward Observatory and Department of Astronomy, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85721, USA; Data Science Institute, University of Arizona , 1230 N. Cherry Avenue, Tucson, AZ 85721, USA; Program in Applied Mathematics, University of Arizona , 617 N. Santa Rita, Tucson, AZ 85721, USAPolarimetric light curves of Sagittarius A* (Sgr A*) sometimes exhibit loops in the Stokes Q and U plane over time, often interpreted as orbiting hotspot motion. In this work, we apply the differential geometry of planar curves to develop a new technique for estimating polarimetric rotation rates. Applying this technique to 230 GHz light curves of Sgr A*, we find evidence of clockwise motion not only during a postflare period on 2017 April 11, as previously discovered, but also during the quiescent days imaged by the Event Horizon Telescope (EHT). The data exhibit a clockwise fraction of 0.65 ± 0.09 and an overall Q − U rotation rate of $-2.6\pm 0.6\,\deg \,{t}_{g}^{-1}$ . We analyze a library of general relativistic magnetohydrodynamic simulations and find that face-on, clockwise-rotating models with strong magnetic fields are most likely to be consistent with the observations. These results are consistent with EHT and GRAVITY Collaboration studies and indirectly support an interpretation in which the polarized image of Sgr A* has been rotated by an external Faraday screen. This technique offers a novel probe of event-horizon-scale dynamics that complements dynamical reconstructions.https://doi.org/10.3847/1538-4357/add729AccretionSupermassive black holesMagnetohydrodynamical simulationsRadiative transfer simulationsPolarimetry |
| spellingShingle | Angelo Ricarte Nicholas S. Conroy Maciek Wielgus Daniel C. M. Palumbo Razieh Emami Chi-Kwan Chan Dynamical Inference from Polarized Light Curves of Sagittarius A* The Astrophysical Journal Accretion Supermassive black holes Magnetohydrodynamical simulations Radiative transfer simulations Polarimetry |
| title | Dynamical Inference from Polarized Light Curves of Sagittarius A* |
| title_full | Dynamical Inference from Polarized Light Curves of Sagittarius A* |
| title_fullStr | Dynamical Inference from Polarized Light Curves of Sagittarius A* |
| title_full_unstemmed | Dynamical Inference from Polarized Light Curves of Sagittarius A* |
| title_short | Dynamical Inference from Polarized Light Curves of Sagittarius A* |
| title_sort | dynamical inference from polarized light curves of sagittarius a |
| topic | Accretion Supermassive black holes Magnetohydrodynamical simulations Radiative transfer simulations Polarimetry |
| url | https://doi.org/10.3847/1538-4357/add729 |
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