Upper Limits on the Isotropic Gravitational-Wave Background from the first part of LIGO, Virgo, and KAGRA's fourth Observing Run
Abstract
We present results from the search for an isotropic gravitational-wave background using Advanced LIGO and Advanced Virgo data from O1 through O4a, the first part of the fourth observing run. This background is the accumulated signal from unresolved sources throughout cosmic history and encodes information about the merger history of compact binaries throughout the Universe, as well as exotic physics and potentially primordial processes from the early cosmos. Our cross-correlation analysis reveals no statistically significant background signal, enabling us to constrain several theoretical scenarios. For compact binary coalescences which approximately follow a 2/3 power-law spectrum, we constrain the fractional energy density to ΩGW(25Hz)≤ 2.0× 10−9 (95% cred.), a factor of 1.7 improvement over previous results. Scale-invariant backgrounds are constrained to ΩGW(25Hz)≤ 2.8× 10−9, representing a 2.1x sensitivity gain. We also place new limits on gravity theories predicting non-standard polarization modes and confirm that terrestrial magnetic noise sources remain below detection threshold. Combining these spectral limits with population models for GWTC-4, the latest gravitational-wave event catalog, we find our constraints remain above predicted merger backgrounds but are approaching detectability. The joint analysis combining the background limits shown here with the GWTC-4 catalog enables improved inference of the binary black hole merger rate evolution across cosmic time. Employing GWTC-4 inference results and standard modeling choices, we estimate that the total background arising from compact binary coalescences is ΩCBC(25Hz)=0.9+1.1−0.5× 10−9 at 90% confidence, where the largest contribution is due to binary black holes only, ΩBBH(25Hz)=0.8+1.1−0.5× 10−9.
Related
- Updated Upper Limits on the Isotropic Gravitational-Wave Background from LIGO, Virgo, and KAGRA Data through April 2025
- In Search of the Gravitational Wave of Fast X-Ray Transient in the Second Part of the LIGO-Virgo-KAGRA Fourth Observing Run
- GWTC-4.0: Updating the Gravitational-wave Transient Catalog with Observations from the First Part of the Fourth LIGO–Virgo–KAGRA Observing Run
- GWTC-5.0: Observations from the Second Part of the Fourth LIGO-Virgo-KAGRA Observing Run and Updates to the Gravitational-Wave Transient Catalog
- Direct multi-model dark-matter search with gravitational-wave interferometers using data from the first part of the fourth LIGO-Virgo-KAGRA observing run
BibTeX
@article{abac2026upper,
title = {{Upper Limits on the Isotropic Gravitational-Wave Background from the first part of LIGO, Virgo, and KAGRA's fourth Observing Run}},
author = {A.G Abac and I Abouelfettouh and F Acernese and K Ackley and C Adamcewicz and S Adhicary and D Adhikari and N Adhikari and R.X Adhikari and V.K Adkins and S Afroz and A Agapito and D Agarwal and M Agathos and N Aggarwal and S Aggarwal and O.D Aguiar and I.-L Ahrend and L Aiello and A Ain and P Ajith and T Akutsu and S Albanesi and W Ali and S Al-Kershi and C Alléné and A Allocca and S Al-Shammari and P.A Altin and S Alvarez-Lopez and W Amar and O Amarasinghe and A Amato and F Amicucci and C Amra and A Ananyeva and S.B Anderson and W.G Anderson and M Andia and M Ando and M Andrés-Carcasona and T Andríc and J Anglin and S Ansoldi and J.M Antelis and S Antier and M Aoumi and E.Z Appavuravther and S Appert and S.K Apple and K Arai and A Araya and M.C Araya and M. Arca Sedda and J.S Areeda and N Aritomi and F Armato and S Armstrong and N Arnaud and M Arogeti},
journal = {Phys.Rev.D},
year = {2026},
month = sep,
doi = {10.1103/wq57-sjt2},
eprint = {2508.20721},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05494867v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Upper Limits on the Isotropic Gravitational-Wave Background from the first part of LIGO, Virgo, and KAGRA's fourth Observing Run
AU - A.G Abac
AU - I Abouelfettouh
AU - F Acernese
AU - K Ackley
AU - C Adamcewicz
AU - S Adhicary
AU - D Adhikari
AU - N Adhikari
AU - R.X Adhikari
AU - V.K Adkins
AU - S Afroz
AU - A Agapito
AU - D Agarwal
AU - M Agathos
AU - N Aggarwal
AU - S Aggarwal
AU - O.D Aguiar
AU - I.-L Ahrend
AU - L Aiello
AU - A Ain
AU - P Ajith
AU - T Akutsu
AU - S Albanesi
AU - W Ali
AU - S Al-Kershi
AU - C Alléné
AU - A Allocca
AU - S Al-Shammari
AU - P.A Altin
AU - S Alvarez-Lopez
AU - W Amar
AU - O Amarasinghe
AU - A Amato
AU - F Amicucci
AU - C Amra
AU - A Ananyeva
AU - S.B Anderson
AU - W.G Anderson
AU - M Andia
AU - M Ando
AU - M Andrés-Carcasona
AU - T Andríc
AU - J Anglin
AU - S Ansoldi
AU - J.M Antelis
AU - S Antier
AU - M Aoumi
AU - E.Z Appavuravther
AU - S Appert
AU - S.K Apple
AU - K Arai
AU - A Araya
AU - M.C Araya
AU - M. Arca Sedda
AU - J.S Areeda
AU - N Aritomi
AU - F Armato
AU - S Armstrong
AU - N Arnaud
AU - M Arogeti
PY - 2026
DA - 2026/09/02
JO - Phys.Rev.D
DO - 10.1103/wq57-sjt2
UR - https://hal.science/hal-05494867v1
AB - We present results from the search for an isotropic gravitational-wave background using Advanced LIGO and Advanced Virgo data from O1 through O4a, the first part of the fourth observing run. This background is the accumulated signal from unresolved sources throughout cosmic history and encodes information about the merger history of compact binaries throughout the Universe, as well as exotic physics and potentially primordial processes from the early cosmos. Our cross-correlation analysis reveals no statistically significant background signal, enabling us to constrain several theoretical scenarios. For compact binary coalescences which approximately follow a 2/3 power-law spectrum, we constrain the fractional energy density to Ω_GW(25Hz)≤ 2.0× 10^−9 (95% cred.), a factor of 1.7 improvement over previous results. Scale-invariant backgrounds are constrained to Ω_GW(25Hz)≤ 2.8× 10^−9, representing a 2.1x sensitivity gain. We also place new limits on gravity theories predicting non-standard polarization modes and confirm that terrestrial magnetic noise sources remain below detection threshold. Combining these spectral limits with population models for GWTC-4, the latest gravitational-wave event catalog, we find our constraints remain above predicted merger backgrounds but are approaching detectability. The joint analysis combining the background limits shown here with the GWTC-4 catalog enables improved inference of the binary black hole merger rate evolution across cosmic time. Employing GWTC-4 inference results and standard modeling choices, we estimate that the total background arising from compact binary coalescences is Ω_CBC(25Hz)=0.9^+1.1_−0.5× 10^−9 at 90% confidence, where the largest contribution is due to binary black holes only, Ω_BBH(25Hz)=0.8^+1.1_−0.5× 10^−9.
ER -