Resampling cross-correlation search of LIGO O4a data sets Sco X-1 continuous-wave upper limits below torque balance (independent of inclination) for 50–200 Hz.
Directional search for per- sistent gravitational waves: Results from the first part of ligo-virgo-kagra’s fourth observing run
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abstract
The angular distribution of gravitational-wave power from persistent sources may exhibit anisotropies arising from the large-scale structure of the Universe. This motivates directional searches for astrophysical and cosmological gravitational-wave backgrounds, as well as continuous-wave emitters. We present results of such a search using data from the first observing run through the first portion of the fourth observing run of the LIGO-Virgo-KAGRA Collaborations. We apply gravitational-wave radiometer techniques to generate skymaps and search for both narrowband and broadband persistent gravitational-wave sources. Additionally, we use spherical harmonic decomposition to probe spatially extended sources. No evidence of persistent gravitational-wave signals is found, and we set the most stringent constraints to date on such emissions. For narrowband point sources, our sensitivity estimate to effective strain amplitude lies in the range $(0.03 - 8.4) \times 10^{-24}$ across all sky and frequency range $(20 - 160)$ Hz. For targeted sources -- Scorpius X-1, SN 1987A, the Galactic Center, Terzan 5, and NGC 6397 -- we constrain the strain amplitude with best limits ranging from $\sim 1.1 \times 10^{-25}$ to $6.5 \times 10^{-24}$. For persistent broadband sources, we constrain the gravitational-wave flux $F_{\alpha, \hat{n}}^{95\%, \mathrm{UL}}(25\, \mathrm{Hz}) < (0.008 - 5.5) \times 10^{-8}\, \mathrm{erg\, cm^{-2}\, s^{-1}\, Hz^{-1}}$, depending on the sky direction $\hat{n}$ and spectral index $\alpha=0,\,2/3,\,3$. Finally, for extended sources, we place upper limits on the strain angular power spectrum $C_\ell^{1/2} < (0.63 - 17) \times 10^{-10} \,\mathrm{sr}^{-1}$.
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A dirty-map space inference method allows recovery of SGWB angular power spectrum parameters from LIGO O3 simulations for strong signals in auto- and cross-correlation searches up to ℓ_max=10.
Third-generation gravitational-wave detectors can constrain frequency-dependent beyond-GR waveform modifications in the stochastic background, but modified propagation effects remain degenerate with astrophysical population parameters.
Hierarchical Bayesian analysis of GWTC-5 binary black hole spins finds no evidence for superradiant axions and excludes masses 1.7e-14 to 3.3e-12 eV at 95% CL.
citing papers explorer
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Sub-Torque-Balance Upper Limits on Continuous Gravitational Waves from Scorpius X-1
Resampling cross-correlation search of LIGO O4a data sets Sco X-1 continuous-wave upper limits below torque balance (independent of inclination) for 50–200 Hz.
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Parameter Estimation of the Gravitational-Wave Angular Power Spectrum in the Dirty-Map Space
A dirty-map space inference method allows recovery of SGWB angular power spectrum parameters from LIGO O3 simulations for strong signals in auto- and cross-correlation searches up to ℓ_max=10.
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Modeling Uncertainties in Modified Gravity Predictions for the Stochastic Gravitational-Wave Background
Third-generation gravitational-wave detectors can constrain frequency-dependent beyond-GR waveform modifications in the stochastic background, but modified propagation effects remain degenerate with astrophysical population parameters.
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No Evidence for Superradiant Axions in LIGO-Virgo-KAGRA GWTC-5 Binary Black Hole Spins
Hierarchical Bayesian analysis of GWTC-5 binary black hole spins finds no evidence for superradiant axions and excludes masses 1.7e-14 to 3.3e-12 eV at 95% CL.