Latetime postmerger modeling of a compact binary: effects of relativity, rprocess heating, and treatment of transport
Abstract
Detectable electromagnetic counterparts to gravitational waves from compact binary mergers can be produced by outflows from the black holeaccretion disk remnant during the first 10 s after the merger. Twodimensional axisymmetric simulations with effective viscosity remain an efficient and informative way to model this latetime postmerger evolution. In addition to the inherent approximations of axisymmetry and modeling turbulent angular momentum transport by a viscosity, previous simulations often make other simplifications related to the treatment of the equation of state and turbulent transport effects. In this paper, we test the effect of these modeling choices. By evolving with the same viscosity the exact postmerger initial configuration previously evolved in Newtonian viscous hydrodynamics, we find that the Newtonian treatment provides a good estimate of the disk ejecta mass but underestimates the outflow velocity. We find that the inclusion of heavy nuclei causes a notable increase in ejecta mass. An approximate inclusion of rprocess effects has a comparatively smaller effect, except for its designed effect on the composition. Diffusion of composition and entropy, modeling turbulent transport effects, has the overall effect of reducing ejecta mass and giving it a speed with lower average and more tightlypeaked distribution. Also, we find significant acceleration of outflow even at distances beyond 10 000 km, so that thermal wind velocities only asymptote beyond this radius and at higher values than often reported.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 April 2023
 DOI:
 10.1088/13616382/acc0c6
 arXiv:
 arXiv:2208.02367
 Bibcode:
 2023CQGra..40h5008H
 Keywords:

 postmerger;
 compact object binary;
 accretion disk;
 kilonovae;
 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 23 pages, 7 figures, version accepted to Classical and Quantum Gravity