Expectations for extreme-mass-ratio bursts from the Galactic Centre

TL;DR

This paper models the expected rate of extreme-mass-ratio bursts from the Galactic Centre and assesses their potential to accurately determine the black hole's mass and spin with space-based gravitational wave detectors.

Contribution

It introduces a simple model to estimate EMRB event rates from the Galactic Centre and evaluates their usefulness for measuring the MBH's properties.

Findings

Approximately 2 detectable bursts expected in a 2-year LISA mission

Stellar black holes dominate the EMRB event rate

Potential to measure MBH mass to ~1% and spin to ~0.1

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. 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 there could be on average ~2 bursts in a two year mission lifetime for LISA. Stellar mass black holes dominate the event rate. Creating a sample of 100 mission realisations, we calculate what we could learn about the MBH. On average, we expect to be able to determine the MBH mass to ~1% and the spin to ~0.1 using EMRBs.