Studying Postmerger Outflows from Magnetized Neutrino-cooled Accretion Disks

TL;DR

This study uses 2D GRMHD simulations to analyze outflows from magnetized, neutrino-cooled accretion disks around black holes post-merger, linking black hole spin and disk properties to outflow strength and electromagnetic signals.

Contribution

It provides the first detailed GRMHD simulation-based analysis of post-merger outflows with realistic physics, connecting black hole spin and disk mass to outflow characteristics and electromagnetic observables.

Findings

Stronger outflows from rapidly spinning black holes with massive disks.

Wind velocities are moderate, around 0.1-0.2c.

Predicted luminosities of transients match previous estimates.

Abstract

Neutrino-cooled accretion flow around a spinning black hole, produced by a compact binary merger is a promising scenario for jet formation and launching magnetically-driven outflows. Based on GW170817 gravitational wave detection by LIGO and Virgo observatories followed by electromagnetic counterparts, this model can explain the central engine of the short duration gamma ray bursts (GRB) and kilonova radiations. Using the open-source GRMHD HARM-COOL code, we evolved several 2D magnetized accretion disk-black hole models with realistic equation of state in the fixed curved space-time background. We applied particle tracer technique to measure the properties of the outflows. The disk and black hole's initial parameters are chosen in a way to represent different possible post-merger scenarios of the merging compact objects. Our simulations show a strong correlation between black hole's spin and ejected mass. Generally, mergers producing massive disks and rapidly spinning black holes launch stronger outflows. We observed our models generate winds with moderate velocity ($v/c \sim 0.1-0.2$), and broad range of electron fraction. We use these results to estimate the luminosity and light curves of possible radioactively powered transients emitted by such systems. We found the luminosity peaks within the range of $10^{40}-10^{42}$ erg/s which agrees with previous studies for disk wind outflows.