Expectations for extreme-mass-ratio bursts from the galactic centre

Abstract

When a compact object on a highly eccentric orbit about a much more massive body passes through periapsis, it emits a short gravitational wave signal known as an extreme-mass-ratio burst (EMRB). We consider stellar mass objects orbiting the massive black hole (MBH) found in the Galactic Centre (GC). EMRBs provide a novel means of extracting information about the MBH; an EMRB from the Galactic MBH could be highly informative regarding the MBH's mass and spin if the orbital periapsis is small enough. However, to be a useful astronomical tool, EMRBs must be both informative and sufficiently common to be detectable with a space-based interferometer. We construct a simple model to predict the event rate for Galactic EMRBs. We estimate that there could be on average ~2 bursts in a two-year mission lifetime for the Laser Interferometer Space Antenna. Stellar mass black holes dominate the event rate. Creating a sample of 100 mission realizations, we calculate what we could learn about the MBH. On average, we expect to be able to determine the MBH mass to ~1 per cent and the spin to ~0.1 using EMRBs. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.