Probing black hole `charge' from the binary black hole inspiral

Abstract

Recent gravitational wave (GW) observations have enabled us to look beyond the standard paradigm of gravitational physics, namely general relativity (GR). Along with the mass and the angular momentum, which typical astrophysical black holes (BHs) are endowed with, theories beyond GR generically induce `charge' to these BHs. Notably, for BHs carrying the extra `charge' hair, we expect the BH absorption effects to modify accordingly and alter the tidal heating terms. Hence, the inclusion of the corrections in the GW waveform model, arising from the BH `charge', allows us to test the consistency of the observed binaries with Kerr BHs in GR. We compute the explicit dependence of the binary inspiral phase on the `charge' parameter arising from the tidal heating effect and study the measurability of the same from GW observations of binary mergers. Specifically, we employ the {\tt TaylorF2} waveform model, which accurately models the inspiral evolution of an aligned-spin binary merger, and Bayesian analysis-based GW data inference to measure the `charge' parameter for a selected set of detected binaries. We also present a detailed simulation study to investigate the possibility of measuring the charge parameter from binaries with different masses, spins and source locations. The analysis of selected GW events from the third GW transient catalogue shows that the `charge' parameter constraints are poor from the observed signals with the current sensitivity. In contrast, the simulation studies indicate that the spinning binaries with significant mass asymmetry provide the best constraints on the BH `charge' parameter. Finally, we study the prospects of measuring the BH `charge' parameter from a future GW detector with improved sensitivity.