Black Hole Mergers from Globular Clusters Observable by LISA and LIGO:\n Results from post-Newtonian Binary-Single Scatterings

We study the gravitational wave (GW) frequency and chirp mass distribution of\nbinary black hole (BBH) mergers assembled through three-body interactions in\nglobular clusters (GCs), when GW emission at the 2.5 post-Newtonian (PN) level\nis included in the $N$-body equation-of-motion (EOM). From performing $\\sim\n2.5\\times10^{6}$ PN binary-single interactions based on GC data from the\n`MOCCA-Survey Database I' project, and by the use of analytical methods, we\nfind that $5-10\\%$ of all the three-body assembled GC BBH mergers have a GW\nfrequency at formation that is $\\gtrsim 10^{-1}$ Hz, implying they enter the\nLIGO band without having drifted through the LISA band first. If PN terms are\nnot included in the EOM, one finds instead that all BBH mergers drifts through\nboth LISA and LIGO. As the fraction of BBH mergers that only show up in LIGO is\nexpected to be $\\sim 0\\%$ for standard field binary BBH mergers, future joint\nmeasurements with LISA and LIGO can be used to gain insight into the formation\nof BBH mergers.\n