Sub-Torque-Balance Upper Limits on Continuous Gravitational Waves from Scorpius X-1
40 affiliations
- 1Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
- 2LIGO Hanford Observatory
- 3Università di Salerno
- 4INFN
- 5University of Warwick
- 6University of Western Australia
- 7Monash University
- 8The Pennsylvania State University
- 9Leibniz Universität Hannover
- 10University of Wisconsin-Milwaukee
- 11California Institute of Technology
- 12Louisiana State University
- 13Tata Institute of Fundamental Research
- 14Centre de Physique Théorique
- 15Université catholique de Louvain
- 16Queen Mary University of London
- 17University of California
- 18University of Minnesota
- 19Instituto Nacional de Pesquisas Espaciais
- 20Université Paris Cité
- 21Università di Roma Tor Vergata
- 22Universiteit Antwerpen
- 23Gravitational Wave Science Project
- 24Advanced Technology Center
- 25Friedrich-Schiller-Universität Jena
- 26INFN Sezione di Torino
- 27Universität Hamburg
- 28Università degli Studi di Genova
- 29Univ. Savoie Mont Blanc
- 30Università di Napoli “Federico II,” I-80126 Napoli,
- 31Cardiff University
- 32Australian National University
- 33Massachusetts Institute of Technology
- 34Maastricht University
- 35Nikhef
- 36Università di Roma “La Sapienza,”
- 37Aix Marseille Univ
- 38Université Paris-Saclay
- 39The University of Tokyo
- 40Gran Sasso Science Institute (GSSI)
Abstract
We present the results of a search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1 using LIGO data from the first part of the fourth LIGO-Virgo-KAGRA observing run. By applying the resampling version of the cross-correlation pipeline to search for signal frequencies f0 between $25$ and 200unHz (corresponding to neutron star spin frequencies of $12.5$ to 100unHz for GW due to triaxiality, or ∼15−20 to ∼120−150unHz for GW due to r-modes), we set upper limits below the standard torque balance level, independent of neutron star spin inclination, for 50unHz≲ f0≲200unHz. While uncertainties in the modelling of torque and equation of state limit the strength of our inference, our results nonetheless argue against torque balance in this spin range for a neutron star described by a hadronic equation of state. The most sensitive upper limits on the gravitational wave amplitude h0, at the upper end of the frequency band searched, approach 5×10−26 marginalized over inclination angle and 2×10−26 assuming the most favorable inclination. The marginalized upper limits correspond to a sensitivity depth of 70−75unHz−1/2, improving sensitivity considerably over previous searches. Expressed as constraints on the triaxial deformation of the neutron star, the limits correspond to an ellipticity of 3×10−5 if the GW frequency f0 is 75unHz and 3×10−6 if f0=200unHz, approaching deformations which could be supported by ordinary nuclear matter. Outliers from the search were ruled out as potential signals by a combination of hierarchical followup and analysis of additional data from later in the observing run.
Related
- Spin wandering of an accreting neutron star near torque balance: implications for gravitational wave searches
- Torque lags from magnetic unlocking in neutron stars and gravitational-wave smearing
- Torque lags from magnetic unlocking in neutron stars and gravitational-wave smearing
- Updated Upper Limits on the Isotropic Gravitational-Wave Background from LIGO, Virgo, and KAGRA Data through April 2025
- Limits on the Inferred Hubble Constant Bias from a Local McVittie Gravitational Field
BibTeX
@article{abac2026subtorquebalance,
title = {{Sub-Torque-Balance Upper Limits on Continuous Gravitational Waves from Scorpius X-1}},
author = {A. G. Abac and I. Abouelfettouh and F. Acernese and K. Ackley and A. Adam 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 L. Albers 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 C. Anand and A. Ananyeva and S. B. Anderson and W. G. Anderson and M. Andia and M. Ando and M. Andrés-Carcasona and J. L. Andrey and T. Andrić and J. Anglin and J. Anna 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 F. Arciprete},
journal = {Astrophys.J.Lett.},
year = {2026},
month = sep,
doi = {10.3847/2041-8213/aea296},
eprint = {2607.07765},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05743968v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Sub-Torque-Balance Upper Limits on Continuous Gravitational Waves from Scorpius X-1
AU - A. G. Abac
AU - I. Abouelfettouh
AU - F. Acernese
AU - K. Ackley
AU - A. Adam
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 - L. Albers
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 - C. Anand
AU - A. Ananyeva
AU - S. B. Anderson
AU - W. G. Anderson
AU - M. Andia
AU - M. Ando
AU - M. Andrés-Carcasona
AU - J. L. Andrey
AU - T. Andrić
AU - J. Anglin
AU - J. Anna
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 - F. Arciprete
PY - 2026
DA - 2026/09/09
JO - Astrophys.J.Lett.
DO - 10.3847/2041-8213/aea296
UR - https://hal.science/hal-05743968v1
AB - We present the results of a search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1 using LIGO data from the first part of the fourth LIGO-Virgo-KAGRA observing run. By applying the resampling version of the cross-correlation pipeline to search for signal frequencies f_0 between $25$ and 200unHz (corresponding to neutron star spin frequencies of $12.5$ to 100unHz for GW due to triaxiality, or ∼15−20 to ∼120−150unHz for GW due to r-modes), we set upper limits below the standard torque balance level, independent of neutron star spin inclination, for 50unHz≲ f_0≲200unHz. While uncertainties in the modelling of torque and equation of state limit the strength of our inference, our results nonetheless argue against torque balance in this spin range for a neutron star described by a hadronic equation of state. The most sensitive upper limits on the gravitational wave amplitude h_0, at the upper end of the frequency band searched, approach 5×10^−26 marginalized over inclination angle and 2×10^−26 assuming the most favorable inclination. The marginalized upper limits correspond to a sensitivity depth of 70−75unHz^−1/2, improving sensitivity considerably over previous searches. Expressed as constraints on the triaxial deformation of the neutron star, the limits correspond to an ellipticity of 3×10^−5 if the GW frequency f_0 is 75unHz and 3×10^−6 if f_0=200unHz, approaching deformations which could be supported by ordinary nuclear matter. Outliers from the search were ruled out as potential signals by a combination of hierarchical followup and analysis of additional data from later in the observing run.
SN - 2041-8205
SN - 2041-8213
ER -