Gravitational waves from bodies orbiting the Galactic Center black hole and their detectability by LISA

2019/03/31 by Eric Gourgoulhon, Alexandre Le Tiec, Frederic H. Vincent +1 · 1 citation
Physics and Astronomy · #gr-qc #astro-ph.HE #astro-ph.SR

paper · pdf · doi:10.1051/0004-6361/201935406

published as A&A 627, A92 (2019) · 27 pages, 22 figures, accepted for publication in Astronomy and Astrophysics; text slightly modified and figures added/changed with respect to v2; see related paper by Amaro-Seoane 2019, arXiv:1903.10871

arxiv created 2019/06/09 · arxiv updated 2019/07/17

Abstract

We present the first fully relativistic study of gravitational radiation from bodies in circular equatorial orbits around the massive black hole at the Galactic Center, Sgr A* and we assess the detectability of various kinds of objects by the gravitational wave detector LISA. Our computations are based on the theory of perturbations of the Kerr spacetime and take into account the Roche limit induced by tidal forces in the Kerr metric. The signal-to-noise ratio in the LISA detector, as well as the time spent in LISA band, are evaluated. We have implemented all the computational tools in an open-source SageMath package, within the Black Hole Perturbation Toolkit framework. We find that white dwarfs, neutrons stars, stellar black holes, primordial black holes of mass larger than 10^-4 M_\odot, main-sequence stars of mass lower than ∼ 2.5 M_\odot and brown dwarfs orbiting Sgr A* are all detectable in one year of LISA data with a signal-to-noise ratio above 10 during at least 10⁵ years in the slow inspiral towards either the innermost stable circular orbit (compact objects) or the Roche limit (main-sequence stars and brown dwarfs). The longest times in-band, of the order of 10⁶ years, are achieved for primordial black holes of mass ∼ 10^-3 M_\odot down to 10^-5 M_\odot, depending on the spin of Sgr A*, as well as for brown dwarfs, just followed by white dwarfs and low mass main-sequence stars. The long time in-band of these objects makes Sgr A* a valuable target for LISA. We also consider bodies on close circular orbits around the massive black hole in the nucleus of the nearby galaxy M32 and find that, among them, compact objects and brown dwarfs stay for 10³ to 10⁴ years in LISA band with a 1-year signal-to-noise ratio above 10.

Citations

• X-MRIs: Extremely Large Mass-Ratio Inspirals

Cited by

• The Environmental Effects on Inspiraling Binary Black Hole Systems in the Centers of the LMC and M31