Extended Data Fig. 2: Magnetorotational instability inside the merger remnant.

(Top) The radial profile of the angular velocity (blue) and the rest-mass density (green) on the equatorial plane at t − t_merger ≈ 50 ms. Magnetorotational instability is inactive in a region with x ≲ 9 km and ρ ≳ 10^14.5 g/cm³. The inset shows the same profiles with the logarithmic scale in the radial direction. (Middle) Magnetorotational instability quality factor in a core region as a function of time. The remnant core is defined by a region with ρ≥10¹³ g/cm³. The blue curve denotes the employed finest grid resolution of 12.5 m. At t − t_merger ≈ 30 ms, the two finest domains with Δx_finest = 12.5 m and Δx_finest = 25 m are removed. Thus, the employed grid resolution is Δx_finest = 50 m plotted with the green curve. At t − t_merger ≈ 50 ms, the finest domain with Δx_finest = 50 m is removed and the subsequent evolution with Δx_finest = 100 m is plotted with the cyan curve. The result with Δx_finest = 200 m is plotted with the purple curve. (Bottom) The same as the middle panel, but for a torus defined by a region with 10⁷ g/cm³≤ρ≤10¹³ g/cm³.