Extreme-mass-ratio bursts from the Galactic Centre

TL;DR

This paper explores how extreme-mass-ratio bursts (EMRBs) from objects near the Galactic Centre's black hole can be detected and used to precisely measure the black hole's mass and spin, enhancing our understanding of galactic nuclei.

Contribution

It demonstrates the detectability of EMRBs from the Galactic Centre and quantifies how these signals can constrain the black hole's parameters, especially for periapses smaller than about 10 gravitational radii.

Findings

EMRBs are detectable if periapsis < 65 r_g.

Signal-to-noise ratio scales with periapsis and mass.

EMRBs can constrain black hole mass and spin for periapses < 10 r_g.

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 the 4.31 \times 10^6 M_sol massive black hole (MBH) in the Galactic Centre. We investigate how EMRBs could constrain the parameters of the Galaxy's MBH. EMRBs should be detectable if the periapsis is r_p < 65 r_g for a \mu = 10 M_sol orbiting object, where r_g = GM/c^2 is the gravitational radius. The signal-to-noise ratio \rho scales like log(\rho) = -2.7 log(r_p/r_g) + log(\mu/M_sol) + 4.9. For periapses smaller than ~ 10 r_g, EMRBs can be informative, providing good constraints on both the MBH's mass and spin.