ITC Colloquium - Hang Yu (Caltech)


Thursday, September 23, 2021, 11:00am to 12:00pm


"Centihertz gravitational-wave astronomy: from hierarchical black-hole triples to ultra-compact white-dwarf binaries"

Future space-borne gravitational-wave (GW) observatories are sensitive to a rich array of astrophysical systems in the centihertz band. Here we focus on two science cases specifically. The first is hierarchical black-hole (BH) triple systems in galactic nuclei. Such a system consists of a stellar-mass inner binary orbiting around a supermassive BH (SMBH). We show that the orbital angular momentum (AM) of the inner binary will precess around the outer orbital AM due to a de Sitter-like effect, which can be observed as modulations on a detector's antenna response to the inner binary's GW emission. Furthermore, the inner binary's GW emission can be lensed by the SMBH repeatedly. Both effects allow us to directly probe the properties of the SMBH such as its mass. We will then discuss ultra-compact white-dwarf binaries as another science case in the centihertz band.  Such a binary is a promising source for multi-messenger astronomy. I will highlight the role of tidal interaction here, which both modifies the frequency evolution rate of the GW signal and creates pulsations in the optical light curve.
See also: Colloquium, 2021-22