Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks
We study magnetically arrested disks (MADs) around rotating black holes (BHs) under the influence of radiative cooling. We introduce a critical value of the mass accretion rate ${\dot{M}}_{{\rm{crit}}}$ for which the cooling by the synchrotron process efficiently radiates the thermal energy of the d...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/adb749 |
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| author | Akshay Singh Damien Bégué Asaf Pe’er |
| author_facet | Akshay Singh Damien Bégué Asaf Pe’er |
| author_sort | Akshay Singh |
| collection | DOAJ |
| description | We study magnetically arrested disks (MADs) around rotating black holes (BHs) under the influence of radiative cooling. We introduce a critical value of the mass accretion rate ${\dot{M}}_{{\rm{crit}}}$ for which the cooling by the synchrotron process efficiently radiates the thermal energy of the disk. We find ${\dot{M}}_{{\rm{crit}}}\approx 1{0}^{-5.5}{\dot{M}}_{{\rm{Edd}}}$ , where ${\dot{M}}_{{\rm{Edd}}}$ is the Eddington mass accretion rate. The normalization constant depends on the saturated magnetic flux and on the ratio of electron to proton temperatures, but not on the BH mass. We verify our analytical estimate using a suite of general relativistic magnetohydrodynamic simulations for a range of BH spin parameters a ∈ {−0.94, −0.5, 0, 0.5, 0.94} and mass accretion rates ranging from $1{0}^{-7}{\dot{M}}_{{\rm{Edd}}}$ to $1{0}^{-4}{\dot{M}}_{{\rm{Edd}}}$ . We numerically observe that the MAD parameter and the jet efficiency vary by a factor of ≈2 as the mass accretion rate increases above ${\dot{M}}_{{\rm{crit}}}$ , which confirms our analytical result. We further detail how the forces satisfying the quasi-equilibrium of the disk change, with the magnetic contribution increasing as the thermal contribution decreases. |
| format | Article |
| id | doaj-art-22c1bc9b41e9449dba5bab25e3ccdef7 |
| institution | DOAJ |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj-art-22c1bc9b41e9449dba5bab25e3ccdef72025-08-20T03:11:25ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019811L1110.3847/2041-8213/adb749Radiative Cooling Changes the Dynamics of Magnetically Arrested DisksAkshay Singh0https://orcid.org/0009-0006-7515-5164Damien Bégué1https://orcid.org/0000-0003-4477-1846Asaf Pe’er2https://orcid.org/0000-0001-8667-0889Bar-Ilan University , Ramat-Gan 5290002, Israel ; akshay.singh@biu.ac.ilBar-Ilan University , Ramat-Gan 5290002, Israel ; akshay.singh@biu.ac.ilBar-Ilan University , Ramat-Gan 5290002, Israel ; akshay.singh@biu.ac.ilWe study magnetically arrested disks (MADs) around rotating black holes (BHs) under the influence of radiative cooling. We introduce a critical value of the mass accretion rate ${\dot{M}}_{{\rm{crit}}}$ for which the cooling by the synchrotron process efficiently radiates the thermal energy of the disk. We find ${\dot{M}}_{{\rm{crit}}}\approx 1{0}^{-5.5}{\dot{M}}_{{\rm{Edd}}}$ , where ${\dot{M}}_{{\rm{Edd}}}$ is the Eddington mass accretion rate. The normalization constant depends on the saturated magnetic flux and on the ratio of electron to proton temperatures, but not on the BH mass. We verify our analytical estimate using a suite of general relativistic magnetohydrodynamic simulations for a range of BH spin parameters a ∈ {−0.94, −0.5, 0, 0.5, 0.94} and mass accretion rates ranging from $1{0}^{-7}{\dot{M}}_{{\rm{Edd}}}$ to $1{0}^{-4}{\dot{M}}_{{\rm{Edd}}}$ . We numerically observe that the MAD parameter and the jet efficiency vary by a factor of ≈2 as the mass accretion rate increases above ${\dot{M}}_{{\rm{crit}}}$ , which confirms our analytical result. We further detail how the forces satisfying the quasi-equilibrium of the disk change, with the magnetic contribution increasing as the thermal contribution decreases.https://doi.org/10.3847/2041-8213/adb749Black hole physicsMagnetohydrodynamical simulationsAccretion |
| spellingShingle | Akshay Singh Damien Bégué Asaf Pe’er Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks The Astrophysical Journal Letters Black hole physics Magnetohydrodynamical simulations Accretion |
| title | Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks |
| title_full | Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks |
| title_fullStr | Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks |
| title_full_unstemmed | Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks |
| title_short | Radiative Cooling Changes the Dynamics of Magnetically Arrested Disks |
| title_sort | radiative cooling changes the dynamics of magnetically arrested disks |
| topic | Black hole physics Magnetohydrodynamical simulations Accretion |
| url | https://doi.org/10.3847/2041-8213/adb749 |
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