Multi-band gravitational wave astronomy: science with joint space- and ground-based observations of black hole binaries

Abstract

Soon after the observation of the first black hole binary (BHB) by advanced LIGO (aLIGO), GW150914, it was realised that such a massive system would have been observable in the milli-Hz (mHz) band few years prior to coalescence. Operating in the frequency range 0.1-100 mHz, the Laser Interferometer Space Antenna (LISA) can potentially detect up to thousands inspiralling BHBs, based on the coalescence rates inferred from the aLIGO first observing run (O1). The vast majority of them (those emitting at f < 10 mHz) will experience only a minor frequency drift during LISA lifetime, resulting in signals similar to those emitted by galactic white dwarf binaries. At f > 10 mHz however, several of them will sweep through the LISA band, eventually producing loud coalescences in the audio-band probed by aLIGO. This contribution reviews the scientific potential of these new class of LISA sources which, in the past few months, has been investigated in several contexts, including multi-messenger and multi-band gravitational wave astronomy, BHB astrophysics, tests of alternative theories of gravity and cosmography.

Gravitational-wave amplitudes for compact binaries in eccentric orbits at the third post-Newtonian order: Memory contributions

“…As soon as LISA will be operating, it will be able to observe compact binaries in our galaxy emitting GWs of much lower frequency. At this point they still are expected to have moderate eccentricities [26,27]. On the other hand, LISA should be able to detect supermassive black hole binaries forming in the aftermath of galaxy mergers.…”

Are stellar-mass black-hole binaries too quiet for LISA?

“…We find an expected SNR threshold ρ thr ∼ 15 for systems merging within 10 yr. Previous work has assumed a threshold ρ thr ∼ 8, similar to that for compact-binary mergers in LIGO (Abbott et al 2016d), and predict a handful of multiband detections (Kyutoku & Seto 2016;Sesana 2017;Gerosa et al 2019). The expected number of events scales as ρ −3 thr .…”

Multiband gravitational-wave event rates and stellar physics

“…The effectiveness of waveform templates to characterize stellar-mass BHs with LISA is also being actively investigated [22]. Whether or not LISA will be able to deliver such revolutionary science crucially depends on the expected rates of multiband BH events [1,23,24]. The scope of this paper is twofold:…”