Radiation pressure role in accreting massive black hole binaries
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| Main Authors: | , , , |
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| Format: | Preprint |
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2025
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| author | Cocchiararo, Fabiola Franchini, Alessia Lupi, Alessandro Sesana, Alberto |
| author_facet | Cocchiararo, Fabiola Franchini, Alessia Lupi, Alessandro Sesana, Alberto |
| contents | We investigate the impact of radiation pressure on the circumbinary discs surrounding accreting massive black hole binaries (MBHBs) at milli-parsec separations, using 3D hyper-Lagrangian resolution hydrodynamic simulations. The circumbinary discs in our simulations evolve under an adiabatic equation of state. The gas temperature is therefore allowed to change through viscous heating, black-body cooling and self-gravity. We take a significant step further by including the contribution of radiation pressure in the simulations. We model binaries with a total mass of $10^6 \, M_{\odot}$, eccentricities $e=0,0.45,0.9$ and mass ratios $q= 0.7, 1$. We find that the radiation pressure significantly alters the vertical and thermal structure of the disc, resulting in a geometrically thinner, therefore colder configuration. This leads to a reduced accretion rate onto the binary and suppresses cavity eccentricity growth and precession in circular equal mass binaries. The binary eccentricity remains approximately constant, while the semi-major axis decreases over time due to net negative torque, regardless of the initial binary orbital parameters. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2508_18349 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Radiation pressure role in accreting massive black hole binaries Cocchiararo, Fabiola Franchini, Alessia Lupi, Alessandro Sesana, Alberto High Energy Astrophysical Phenomena Cosmology and Nongalactic Astrophysics 85A30 We investigate the impact of radiation pressure on the circumbinary discs surrounding accreting massive black hole binaries (MBHBs) at milli-parsec separations, using 3D hyper-Lagrangian resolution hydrodynamic simulations. The circumbinary discs in our simulations evolve under an adiabatic equation of state. The gas temperature is therefore allowed to change through viscous heating, black-body cooling and self-gravity. We take a significant step further by including the contribution of radiation pressure in the simulations. We model binaries with a total mass of $10^6 \, M_{\odot}$, eccentricities $e=0,0.45,0.9$ and mass ratios $q= 0.7, 1$. We find that the radiation pressure significantly alters the vertical and thermal structure of the disc, resulting in a geometrically thinner, therefore colder configuration. This leads to a reduced accretion rate onto the binary and suppresses cavity eccentricity growth and precession in circular equal mass binaries. The binary eccentricity remains approximately constant, while the semi-major axis decreases over time due to net negative torque, regardless of the initial binary orbital parameters. |
| title | Radiation pressure role in accreting massive black hole binaries |
| topic | High Energy Astrophysical Phenomena Cosmology and Nongalactic Astrophysics 85A30 |
| url | https://arxiv.org/abs/2508.18349 |