Gravitational-Wave Microlensing as a Probe of Compact Object Population
Abstract
The abundance of compact objects ranging from stellar to intermediate masses (∼ 1 − 105M⊙) remains poorly constrained, particularly for populations such as primordial black holes and dark matter subhalos that emit little or no electromagnetic radiation. Gravitational-wave (GW) microlensing provides a complementary way to probe these populations through wave-optics effects imprinted on the GW signals, with implications for astrophysical and cosmological inference. We develop a hierarchical Bayesian framework to infer the population properties of microlenses from an ensemble of microlensed GW events, constraining the slope of the power-law lens mass function (αML), the lens number density (n0), and the fraction of dark matter in compact lenses (fDM). Using simulated microlensed GW signals drawn from a realistic binary black hole population, we find that ∼ 100 detected microlensed events are able to constrain both αML and n0, although a degeneracy between the two remains. For a low-mass-dominated lens population (αML=2) with n0=106 Mpc−3, a three-year observation at the O4 sensitivity yields ∼ 130 detectable microlensed events and recovers the injected dark-matter fraction, fDM≃ 1.2 × 10−4, with a 90% credible interval of 7.3 × 10−5 ≲ fDM ≲ 1.8 × 10−4.
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BibTeX
@misc{seo2026gravitationalwave,
title = {{Gravitational-Wave Microlensing as a Probe of Compact Object Population}},
author = {Eungwang Seo and Jose María Ezquiaga and Martin Hendry},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05947},
eprint = {2611.05947},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05947},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Gravitational-Wave Microlensing as a Probe of Compact Object Population
AU - Eungwang Seo
AU - Jose María Ezquiaga
AU - Martin Hendry
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.05947
UR - https://arxiv.org/abs/2611.05947
AB - The abundance of compact objects ranging from stellar to intermediate masses (∼ 1 − 10^5M_⊙) remains poorly constrained, particularly for populations such as primordial black holes and dark matter subhalos that emit little or no electromagnetic radiation. Gravitational-wave (GW) microlensing provides a complementary way to probe these populations through wave-optics effects imprinted on the GW signals, with implications for astrophysical and cosmological inference. We develop a hierarchical Bayesian framework to infer the population properties of microlenses from an ensemble of microlensed GW events, constraining the slope of the power-law lens mass function (α_ML), the lens number density (n_0), and the fraction of dark matter in compact lenses (f_DM). Using simulated microlensed GW signals drawn from a realistic binary black hole population, we find that ∼ 100 detected microlensed events are able to constrain both α_ML and n_0, although a degeneracy between the two remains. For a low-mass-dominated lens population (α_ML=2) with n_0=10^6 Mpc^−3, a three-year observation at the O4 sensitivity yields ∼ 130 detectable microlensed events and recovers the injected dark-matter fraction, f_DM≃ 1.2 × 10^−4, with a 90% credible interval of 7.3 × 10^−5 ≲ f_DM ≲ 1.8 × 10^−4.
ER -