Relativistic Mergers of Supermassive Black Holes and Their Electromagnetic Signatures

Abstract

Coincident detections of electromagnetic (EM) and gravitational wave (GW) signatures from coalescence events of supermassive black holes are the next observational grand challenge. Such detections will provide the means to study cosmological evolution and accretion processes associated with these gargantuan compact objects. More generally, the observations will enable testing general relativity in the strong, nonlinear regime and will provide independent cosmological measurements to high precision. Understanding the conditions under which coincidences of EM and GW signatures arise during supermassive black hole mergers is therefore of paramount importance. As an essential step towards this goal, we present results from the first fully general relativistic, hydrodynamical study of the late inspiral and merger of equal-mass, spinning supermassive black hole binaries in a gas cloud. We find that variable EM signatures correlated with GWs can arise in merging systems as a consequence of shocks and accretion combined with the effect of relativistic beaming. The most striking EM variability is observed for systems where spins are aligned with the orbital axis and where orbiting black holes form a stable set of density wakes, but all systems exhibit some characteristic signatures that can be utilized in searches for EM counterparts. In the case of the most massive binaries observable by the Laser Interferometer Space Antenna, calculated luminosities imply that they may be identified by EM searches to z ≈ 1, while lower mass systems and binaries immersed in low density ambient gas can only be detected in the local universe.

Electromagnetic partner of the gravitational signal during accretion onto black holes

“…This behaviour might be related with another scaling observed in [13]. In that work, the authors considered the collision of two charged black holes with opposite charge Q and mass M such that 2) . For a distant observer, however, the scenario is that there is an electromagnetic signal coming from an almost stationary black hole, very similar to our final set-up when the charged particles have fallen into the hole.…”

IsJenough? Comparison of gravitational waves emitted along the total angular momentum direction with other preferred orientations

“…Initial data was evolved with Maya, which was used in previous BBH studies [28][29][30][31][32][33][34][35][36]. The grid structure for each run consisted of 10 levels of refinement provided by CARPET [37], a mesh refinement package for CACTUS [38].…”

Relativistic Dynamics and Mass Exchange in Binary Black Hole Mini-disks

“…Initial work focused on matter accreting directly from a circumbinary disk to the BHs during the few binary orbits immediately preceding merger. These investigations were "proof of principle" calculations, designed to show that gas dynamics and full solution of the Einstein Field Equations could be done in tandem (Bode et al 2010;Palenzuela et al 2010;Farris et al 2011;Bode et al 2012;Farris et al 2012;Giacomazzo et al 2012;Gold et al 2014). However, because of their brief duration, the total mass transferred from the circumbinary disk to the central cavity was relatively small and no formation of individual disks around the BHs was observed.…”