# Limits on electromagnetic counterparts of gravitational wave-detected binary black hole mergers

## TL;DR

This paper investigates the potential electromagnetic signals from binary black hole mergers, using simulations to set limits on jet energies and properties based on existing and future observations, despite the lack of expected EM counterparts.

## Contribution

It provides the first systematic limits on jet energetics and Lorentz factors for BBH mergers, based on population simulations and observational constraints.

## Key findings

- Limits on jet energy and Lorentz factors derived from current EM follow-ups.
- Predictions for future EM observations to improve constraints.
- Constraints imply most BBH mergers do not produce bright EM counterparts.

## Abstract

Unlike mergers of two compact objects containing a neutron star (NS), binary black hole (BBH) mergers are not accompanied by the production of tidally disrupted material, and hence lack the most direct source of accretion to power a jet and generate electromagnetic (EM) radiation. However, following a tentative detection by the Fermi GBM of a $\gamma$-ray counterpart to GW150914, several alternative ideas were proposed for driving a jet and producing EM radiation. {\em If} such jets were in fact produced, they would however lack the bright cocoon emission that makes jets from binary NSs bright also at large viewing angles. Here, via Monte Carlo simulations of a population of BBH mergers with properties consistent with those inferred from the existing LIGO/Virgo observations, and the angular emission characteristic of jets propagating into the interstellar medium, we derive limits on the allowed energetics and Lorentz factors of such jets from EM follow ups to GW-detected BBH merger events to date, and we make predictions which will help tighten these limits with broadband EM follow ups to events in future LIGO/Virgo runs. The condition that $\lesssim 1$ event out of 10 GW-detected BBH mergers be above the Fermi/GBM threshold imposes that any currently allowed emission model has to satisfy the condition $E_{\rm iso}/(10^{49} {\rm erg})(\theta_{jet}/20^\circ)\lesssim 1$.