Anisotropic multimessenger signals from black hole neutrino-dominated accretion flows with outflows in binary compact object mergers

TL;DR

This paper explores the anisotropic multimessenger signals, including neutrinos, gravitational waves, and kilonovae, from black hole accretion systems formed after compact object mergers, highlighting their observational signatures and dependencies.

Contribution

It introduces a comprehensive analysis of anisotropic multimessenger signals from NDAFs with outflows, emphasizing their potential for multimessenger astronomy and observational verification.

Findings

DOD kilonovae are dimmer than AT 2017gfo and depend on viewing angles.

High-energy neutrinos are deflected at large viewing angles due to relativistic effects.

GW strains from anisotropic neutrinos increase with viewing angle.

Abstract

A black hole (BH) hyperaccretion system might be born after the merger of a BH and a neutron star (NS) or a binary NS (BNS). In the case of a high mass accretion rate, the hyperaccretion disk is in a state of neutrino-dominated accretion flow (NDAF) and emits numerous anisotropic MeV neutrinos. Only a small fraction of these neutrinos annihilates in the space outside of the disk and then launch ultrarelativistic jets that break away from the merger ejecta to power gamma-ray bursts. Mergers and their remnants are generally considered sources of gravitational waves (GWs), neutrinos, and kilonovae. Anisotropic neutrino emission and anisotropic high-velocity material outflows from central BH-NDAF systems can also trigger strong GWs and luminous disk-outflow-driven (DOD) kilonovae, respectively. In this paper, the anisotropic multimessenger signals from NDAFs with outflows, including DOD kilonovae, MeV neutrinos, and GWs, are presented. As the results, the typical AB magnitude of the DOD kilonovae is lower than that of AT 2017gfo at the same distance, and it decreases with increasing viewing angles and its anisotropy is not sensitive to the outflow mass distribution but mainly determined by the velocity distribution. Since neutrinos with $\gtrsim 10~\rm MeV$ are mainly produced in the inner region of the disk, they will be dramatically deflected to a large viewing angle by relativity effects. Moreover, the strains of GWs induced by anisotropic neutrinos increase with increasing viewing angles. The accumulation of multimessenger detection of the BH-NS/BNS mergers with different viewing angles might further verify the existence of NDAFs with outflows.