Probing supermassive black hole binaries with pulsar timing

摘要

Supermassive black hole (SMBH)mergers are the strongest sources ofgravitational-waves (GWs) in theUniverse. SMBH mergers are expectedto follow galaxy mergers, since likely allmassive galaxies host central SMBHs (see,for example, ref.). Briefly, the black holesfall to the centre of the newly formed galaxythrough dynamical friction and forma binary. This binary should harden byejecting stars crossing its orbit - a processcalled stellar hardening. When the binary isseparated by a centiparsec to a milliparsec,GWs drive the binary to merge. These stepsare described in more detail in ref..