TY - JOUR

T1 - How post-Newtonian dynamics shape the distribution of stationary binary black hole LISA sources in nearby globular clusters

AU - Samsing, Johan

AU - D'Orazio, Daniel J.

PY - 2019/3/15

Y1 - 2019/3/15

N2 - We derive the observable gravitational wave (GW) peak frequency (f) distribution of binary black holes (BBHs) that currently reside inside their globular clusters (GCs), with and without 2.5 post-Newtonian (2.5 PN) effects included in the dynamical evolution of the BBHs. Recent Newtonian studies have reported that a notable number of nearby nonmerging BBHs, i.e., those BBHs that are expected to undergo further dynamical interactions before merger, in GCs are likely to be observable by LISA. However, our 2.5 PN calculations show that the distribution of logf for the nonmerging BBH population above ∼10-3.5 Hz scales as f-34/9 instead of the f-2/3 scaling found in the Newtonian case. This leads to a reduction of approximately 2 orders of magnitude in the expected number of GW sources at ∼10-3 Hz, which leads us to conclude that observing nearby BBHs with LISA is not as likely as has been claimed in the recent literature. In fact, our results suggest that it might be more likely that LISA detects the population of BBHs that will merge before undergoing further interactions. This interestingly suggests that the BBH merger rate derived from LIGO can be used to forecast the number of nearby LISA sources, as well as providing insight into the fraction of BBH mergers forming in GCs.

AB - We derive the observable gravitational wave (GW) peak frequency (f) distribution of binary black holes (BBHs) that currently reside inside their globular clusters (GCs), with and without 2.5 post-Newtonian (2.5 PN) effects included in the dynamical evolution of the BBHs. Recent Newtonian studies have reported that a notable number of nearby nonmerging BBHs, i.e., those BBHs that are expected to undergo further dynamical interactions before merger, in GCs are likely to be observable by LISA. However, our 2.5 PN calculations show that the distribution of logf for the nonmerging BBH population above ∼10-3.5 Hz scales as f-34/9 instead of the f-2/3 scaling found in the Newtonian case. This leads to a reduction of approximately 2 orders of magnitude in the expected number of GW sources at ∼10-3 Hz, which leads us to conclude that observing nearby BBHs with LISA is not as likely as has been claimed in the recent literature. In fact, our results suggest that it might be more likely that LISA detects the population of BBHs that will merge before undergoing further interactions. This interestingly suggests that the BBH merger rate derived from LIGO can be used to forecast the number of nearby LISA sources, as well as providing insight into the fraction of BBH mergers forming in GCs.

UR - http://www.scopus.com/inward/record.url?scp=85064049230&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.99.063006

DO - 10.1103/PhysRevD.99.063006

M3 - Journal article

AN - SCOPUS:85064049230

VL - 99

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 6

M1 - 063006

ER -