Observing the galaxy's massive black hole with gravitational wave bursts

Abstract

An extreme-mass-ratio burst (EMRB) is a gravitational wave signal emitted when a compact object passes through periapsis on a highly eccentric orbit about a much more massive body, in our case a stellar mass object about a 106M⊙ black hole. EMRBs are a relatively unexplored means of probing the space-time of massive black holes (MBHs).We conduct an investigation of the properties of EMRBs and how they could allow us to constrain the parameters, such as spin, of the Galaxy's MBH. We find that if an EMRB event occurs in the Galaxy, it should be detectable for periapse distances rp < 65rg for a μ = 10M⊙ orbiting object, where rg = GM /c2 is the gravitational radius. The signal-to-noise ratio scales as log -2.7 log (rp/rg) + log (μ/Mȯ) + 4.9. For periapses rp 10rg, EMRBs can be informative, and provide good constraints on both the MBH's mass and spin. Closer orbits provide better constraints, with the best giving accuracies of better than one part in 104 for both the mass and spin parameter.