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arXiv · 2609.21136

Effects of Physical Cooling on the Structure of Circumbinary Disks

Minjae V. Kim·Julian H. Krolik·Scott C. Noble
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Abstract

Radiation pressure and radiative cooling often play an important role in deciding the structure and dynamics of astrophysical objects. In this paper, we present a radiative MHD simulation of a circumbinary disk (CBD) around an equal-mass SMBBH. It employs an approximate thermodynamic model based on local thermodynamic equilibrium and diffusion cooling which captures how the internal energy evolves in an optically thick region. The disk reaches a quasi-steady state within $r=5a$ whose mass distribution differs substantially from the one obtained from simulations without physical thermodynamics: the local maximum in the azimuthally-averaged surface density and the lump are completely erased; the time-averaged inner edge becomes more eccentric; and the vertical density distribution depends strongly on the radius. These changes are attributable to the enhancement of the magnetic fields caused by the cooling-driven vertical compression of the disk. Our result emphasizes that the basic properties of the inner CBD are sensitive to both radiation and magnetic physics.

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Minjae V. Kim, Julian H. Krolik, Scott C. Noble. 2026-09-17. Effects of Physical Cooling on the Structure of Circumbinary Disks. https://arxiv.org/abs/2609.21136

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