Limits on Electromagnetic Counterparts of Gravitational-wave-detected Binary Black Hole Mergers

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 γ -ray counterpart to GW150914, several ideas were proposed for driving a jet and producing EM radiation. If such jets were in fact produced, they would, however, lack the cocoon emission that makes jets from binary NSs also bright 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 that will help tighten these limits with broadband EM follow-ups to events in future LIGO/Virgo runs. The condition that ≲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 iso /10 49 erg)( θ jet /20°) ≲ 1.