Gravitational radiation from extreme-mass ratio inspirals in bald kinetic gravity braiding

Abstract

A small compact object orbitting a supermassive black hole or, generically, an extreme-mass ratio inspiral (EMRI) is a primary target of future space-based gravitational wave observatory LISA which aims to sweep for gravitational waves in the frequency band 10^-4 — 10^-1 Hz. In this paper, we compute the gravitational wave energy fluxes for circular EMRIs in the larger sector of kinetic gravity braiding (KGB) susceptible to the no-hair theorem, i.e. bald theories. We show that in the bald limit the kinetic gravity braiding's only residue on the background spacetime is a cosmological constant and the EMRI problem reduces to that of a metric perturbation, characterizing the small compact object, and a massless minimally-coupled scalar field perturbation propagating in a Schwarzschild-de Sitter black hole. We study the effects of KGBs residue on the energy fluxes and the time spent per orbit of the small compact object before it plunges down the supermassive black hole.