Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence
We present the results of four magnetohydrodynamic simulations and one alpha-disk simulation of accretion disks in a compact binary system, neglecting vertical stratification and assuming a locally isothermal equation of state. We demonstrate that in the presence of a net vertical field, disks that...
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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/ad9ddb |
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| author | Morgan Ohana Yan-Fei Jiang Omer Blaes Bryance Oyang |
| author_facet | Morgan Ohana Yan-Fei Jiang Omer Blaes Bryance Oyang |
| author_sort | Morgan Ohana |
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| description | We present the results of four magnetohydrodynamic simulations and one alpha-disk simulation of accretion disks in a compact binary system, neglecting vertical stratification and assuming a locally isothermal equation of state. We demonstrate that in the presence of a net vertical field, disks that extend out to the 3:1 mean-motion resonance grow eccentricity in full MHD in much the same way as in hydrodynamical disks. Hence, turbulence due to the magnetorotational instability (MRI) does not impede the tidally driven growth of eccentricity in any meaningful way. However, we find two important differences with alpha-disk theory. First, in MHD, eccentricity builds up in the inner disk with a series of episodes of radial disk-breaking into two misaligned eccentric disks, separated by a region of circular orbits. Standing eccentric waves are often present in the inner eccentric disk. Second, the successful spreading of an accretion disk with MRI turbulence out to the resonant radius is nontrivial—and much harder than spreading an alpha disk. This is due to the tendency to develop overdense rings in which tidal torques overwhelm MRI transport and truncate the disk too early. We believe that the inability to spread the disk sufficiently was the reason why our previous attempt to excite eccentricity via the 3:1 mean-motion resonance with MHD failed. Exactly how MHD disks successfully spread outward in compact binary systems is an important problem that has not yet been understood. |
| format | Article |
| id | doaj-art-9e1bab0aa81a41b38b4ede13949c3e1e |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-9e1bab0aa81a41b38b4ede13949c3e1e2025-08-20T02:09:05ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979212810.3847/1538-4357/ad9ddbSimulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic TurbulenceMorgan Ohana0Yan-Fei Jiang1https://orcid.org/0000-0002-2624-3399Omer Blaes2https://orcid.org/0000-0002-8082-4573Bryance Oyang3Department of Physics, University of California , Santa Barbara, CA 93106, USACenter for Computational Astrophysics, Flatiron Institute , New York, NY 10010, USADepartment of Physics, University of California , Santa Barbara, CA 93106, USADepartment of Physics, University of California , Santa Barbara, CA 93106, USAWe present the results of four magnetohydrodynamic simulations and one alpha-disk simulation of accretion disks in a compact binary system, neglecting vertical stratification and assuming a locally isothermal equation of state. We demonstrate that in the presence of a net vertical field, disks that extend out to the 3:1 mean-motion resonance grow eccentricity in full MHD in much the same way as in hydrodynamical disks. Hence, turbulence due to the magnetorotational instability (MRI) does not impede the tidally driven growth of eccentricity in any meaningful way. However, we find two important differences with alpha-disk theory. First, in MHD, eccentricity builds up in the inner disk with a series of episodes of radial disk-breaking into two misaligned eccentric disks, separated by a region of circular orbits. Standing eccentric waves are often present in the inner eccentric disk. Second, the successful spreading of an accretion disk with MRI turbulence out to the resonant radius is nontrivial—and much harder than spreading an alpha disk. This is due to the tendency to develop overdense rings in which tidal torques overwhelm MRI transport and truncate the disk too early. We believe that the inability to spread the disk sufficiently was the reason why our previous attempt to excite eccentricity via the 3:1 mean-motion resonance with MHD failed. Exactly how MHD disks successfully spread outward in compact binary systems is an important problem that has not yet been understood.https://doi.org/10.3847/1538-4357/ad9ddbStellar accretion disksMagnetohydrodynamicsCataclysmic variable stars |
| spellingShingle | Morgan Ohana Yan-Fei Jiang Omer Blaes Bryance Oyang Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence The Astrophysical Journal Stellar accretion disks Magnetohydrodynamics Cataclysmic variable stars |
| title | Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence |
| title_full | Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence |
| title_fullStr | Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence |
| title_full_unstemmed | Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence |
| title_short | Simulations of Eccentricity Growth in Compact Binary Accretion Disks with Magnetohydrodynamic Turbulence |
| title_sort | simulations of eccentricity growth in compact binary accretion disks with magnetohydrodynamic turbulence |
| topic | Stellar accretion disks Magnetohydrodynamics Cataclysmic variable stars |
| url | https://doi.org/10.3847/1538-4357/ad9ddb |
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