Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2607.19273

Calibration of the AdvancedVirgo+ Gravitational Wave Detector and Reconstruction of the Detector Strain h(t) during the Observing Run O4

Virgo Collaboration
View original source ↗Read source document ↗Export metadata ↓

Abstract

From 10 April 2024 15:00 UTC to 18 November 2025 16:00 UTC, the AdvancedVirgo+ gravitational wave detector participated in the LIGO-Virgo-KAGRA O4 observing run, started on 24 May 2023 15:00 UTC. Around 173 transient gravitational wave (GW) sources, all corresponding to coalescences of binary compact objects involving black holes and neutron stars, were detected online during the two run periods O4b and O4c when Virgo was taking data in the detector network. Despite its sensitivity being limited around 55 Mpc, the inclusion of Virgo into the network allowed to improve the accuracy of the source parameter estimation, in particular the sky localisation of the detected events. This article describes the AdvancedVirgo+ detector calibration and the reconstruction of the detector strain h(t) during O4, as well as the estimation of the associated frequency-dependent uncertainties. The detector calibration is based on auxiliary actuators, Newtonian Calibrators and Photon Calibrators, described in other publications. The h(t) reconstruction, including linear noise subtraction, was processed online with a latency of about 10 s. The so-called AnalysisReady strain data were then produced offline. Most of the time, the strain time series was a copy of the online time series, but with updated frequency-dependent uncertainties, around 2-3% in amplitude and below 30 mrad in phase in the 10-2000 Hz frequency band, with the exception of larger uncertainties around 50 Hz and 150 Hz. The AnalysisReady strain data and associated uncertainties have been used for the offline LIGO-Virgo-KAGRA data analysis and are also the data made publicly available through the Gravitational Wave Open Science Center (GWOSC).

Explore related subjects

gr-qc

Keep this discovery

BibTeXRIS

Virgo Collaboration. 2026-07-21. Calibration of the AdvancedVirgo+ Gravitational Wave Detector and Reconstruction of the Detector Strain h(t) during the Observing Run O4. https://arxiv.org/abs/2607.19273

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Electrovacuum Black Hole Uniqueness

We prove the black hole uniqueness conjecture in the axially symmetric, stationary, electrovacuum setting, subject to the refined asymptotic analysis of the associated singular harmonic maps, which includes an analyticity hypothesis at the axes. More precisely, it is shown that any asymptotically flat solution of the Einstein--Maxwell equations in this class, with more than one black hole horizon component is either: Majumdar--Papapetrou, up to a duality rotation, in which case all logarithmic angle defects vanish, or every finite axis rod logarithmic angle defect is strictly negative and hence every interaction force is strictly attractive. The proof extends the singular harmonic map method used for vacuum Kerr uniqueness in [18].

gr-qc↗
arXiv2026

Constraining Modified Mass-to-Horizon Cosmology Through Primordial Inflationary Observables

We investigate slow-roll inflation in a modified cosmological framework inspired by a generalized mass-to-horizon relation (MHR), $M=\gamma {c^2 L^n}/{G}$, where $n$ is a real parameter and $\gamma$ a dimensional constant. Using Padmanabhan's emergence paradigm, we derive the modified Friedmann equations for a flat FRW universe and analyze the dynamics of a canonical scalar field (inflaton) under the slow-roll approximation. We study the resulting inflationary phenomenology for power-law and Starobinsky potentials. For power-law potentials, the MHR modification fails to reconcile these models with current CMB constraints on $r$ and $n_s$. In contrast, Starobinsky inflation exhibits significant sensitivity to deviations from $n=1$. A perturbative analysis ($n=1+\Delta$) yields corrections to inflationary observables. We observe that the scalar power-spectrum normalization, under a fixed-Starobinsky prescription, imposes the stringent constraint $0.960 \lesssim n \lesssim 1.040$ for $N=60$ efolds. This is considerably tighter than spectral-index bounds. Our results establish inflation, particularly Starobinsky-like models, as a sensitive probe of generalized horizon thermodynamics and departures from standard MHR scaling.

gr-qc↗
arXiv2026

Improving the Sensitivity of Gravitational Wave Detection with Weighted Conformal Prediction

In the last decade, kilometre-scale interferometric gravitational-wave detectors have observed hundreds of compact binary mergers, the majority of which are binary black holes. However, the data are noise-dominated, and multiple independent search algorithms (pipelines) are used to enhance sensitivity and improve robustness. Rather than the standard approach of selecting the most significant pipeline output, we combine the outputs from all pipelines using a conformal prediction-based framework to provide statistically rigorous confidence estimates for candidate events. While combining pipelines improves sensitivity and ranking robustness, it requires a principled statistical framework that remains valid as data properties evolve across observing runs. A key challenge is distribution shifts between simulated datasets used for training and calibration and the real, unlabelled, observations used for testing, which can invalidate coverage guarantees and bias confidence estimates. In this work, we address this challenge by incorporating likelihood-ratio reweighting into our conformal prediction framework to account for covariate shift. Using mock datasets containing simulated signals, we demonstrate that weighted conformal prediction restores well-calibrated coverage under covariate shift and increases the confidence of events near the detection threshold, recovering true signals that would otherwise be missed.

gr-qc↗