arXiv subjects

Thierry Pradier

Publications and source records attributed to Thierry Pradier.

16 recordsLinked to original sources

arXiv2025

From the Virgo interferometer calibration to the bias and uncertainty of the h(t) detector strain during the O4 run

Since the first gravitational wave detection in 2015, ground-based interferometer sensitivities have significantly improved, requiring highly precise calibration to ensure accurate reconstruction of the h(t) strain signal. In this talk we will outline the Virgo interferometer calibration steps performed in preparation of the O4b run started in April 2024. We will first describe the Photon Calibrator power devices intercalibration allowing for a 0.48% precision on mirror displacement. Before explaining how the Photon Calibrator is used to calibrate every Virgo mirror actuators. We will also discuss the monitoring of the h(t) strain reconstruction during the run showing that, on the 10 Hz to 2 kHz band, the reconstructed strain achieves a precision of 2% in modulus and 30 mrad in phase. Special emphasis will be given on the newly developed frequency-dependent bias and uncertainty computation method and the resulting online unbiasing of the h(t) strain.

physics.ins-det↗

arXiv2024

The Virgo Newtonian calibration system for the O4 observing run

After initial tests performed during previous observing runs, a Newtonian Calibrator (NCal) system was developed and installed on the Virgo gravitational wave detector for the O4 observing run. This system, which is continuously operated, provides the absolute calibration of Virgo for this run. Its $1\mbox{-}σ$ uncertainty of $0.17\%$ on the amplitudes of the injected signals is better than that obtained with other calibration techniques like the photon calibrator (PCal). This paper presents this NCal system and details the different sources of uncertainties

gr-qc↗

arXiv2023

Estimating source distances for high-energy neutrinos: A method for improving electromagnetic follow-up searches

High-energy neutrino telescopes such as IceCube or KM3NeT issue public alerts describing the characteristics of possible astrophysical high-energy neutrino events. This information, particularly with respect to the arrival direction and the associated uncertainty of the neutrino candidates, is used by observatories to search for possible electromagnetic counterparts. Such searches are complicated by the size of localisation areas, which can be up to tens of squared degrees or more, coupled with the absence of constraints on the distance or nature of the possible source - in contrast to gravitational wave alerts issued by instruments such as LIGO/Virgo. Here, we describe a method for deriving a probable distance interval for the astrophysical source that may possibly be associated with a HEN event, which may then be used in a cross-matching with galaxy catalogues to search for plausible electromagnetic counterparts. This study is intended to serve as a guide for high-energy neutrino followup campaigns.

astro-ph.HE↗

arXiv2021

Newtonian calibrator tests during the Virgo O3 data taking

The gravitational-wave detectors outputs from the LIGO and Virgo collaborations have been a source of scientific results of prime importance in various domains such as astrophysics, cosmology or fundamental physics. With the upgrades of the detectors and their improved sensitivities, new challenges are set for these instruments calibration. A calibration method based on the local variations of the Newtonian gravitational field could be the next absolute reference of calibration for the interferometers network. We report new tests of Newtonian calibrators (NCal) on the Advanced Virgo detector performed during the LIGO-Virgo observing run O3. The NCal-induced strain on a mirror of the interferometer has been computed both using analytical calculations and numerical simulations with results in very good agreement. The strains given by the numerical model have been used to analyse the data of the NCals and have been compared to the reference method of calibration using photon radiation pressure. New methods to measure the NCal to mirror distance and the NCal offset with respect to the plane of the interferometer using two NCals are also presented and used to correct the NCal data which improves the agreement with the current Advanced Virgo reference of calibration.

gr-qc↗

arXiv2019

ANTARES search for high-energy neutrinos from TeV-emitting blazars, Markarian 421 and 501, in coincidence with HAWC gamma-ray flares

An updated analysis of a targeted search for high-energy neutrinos from Markarian 421 and Markarian 501 is reported. They are two of the closest and brightest extragalactic sources in the TeV band. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability. Such radio-loud active galactic nuclei are candidate sources of the observed high-energy cosmic rays. Because their jet is collimated to our line of sight, the hadronic interactions with the surrounding medium can produce an accompanying neutrino and gamma-ray flux. The recent detection of high-energy neutrinos from the direction of TXS 0506+056 motivates a search for high-energy neutrinos from blazars with enhanced gamma-ray activity. These two targeted blazars are subject to long-term monitoring campaigns by the HAWC TeV gamma-ray observatory located in Mexico. This contribution presents the latest results of a search and extends previously presented results to a longer period that covers ANTARES data collected between November 2014 and December 2017. The gamma-ray light curves of each source were used to search for temporally correlated neutrinos, potentially produced in hadronic processes.

astro-ph.HE↗

arXiv2018

Search for high-energy neutrino emission from Mrk 421 and Mrk 501 with the ANTARES neutrino telescope

ANTARES is the largest high-energy neutrino telescope in the Northern Hemisphere. This contribution presents the results of a search, based on the ANTARES data collected over 17 months between November 2014 and April 2016, for high energy neutrino emission in coincidence with TeV $γ$-ray flares from Markarian 421 and Markarian 501, two bright BL Lac extragalactic sources highly variable in flux, detected by the HAWC observatory. The analysis is based on an unbinned likelihood-ratio maximization method. The $γ$-ray lightcurves (LC) for each source were used to search for temporally correlated neutrinos, that would be produced in pp or p-$γ$ interactions. The impact of different flare selection criteria on the discovery neutrino flux is discussed. Plausible neutrino spectra derived from the observed $γ$-ray spectra in addition to generic spectra $E^{-2}$ and $E^{-2.5}$ are tested.

astro-ph.HE↗

arXiv2012

Multimessenger Science Reach and Analysis Method for Common Sources of Gravitational Waves and High-energy Neutrinos

We present the baseline multimessenger analysis method for the joint observations of gravitational waves (GW) and high-energy neutrinos (HEN), together with a detailed analysis of the expected science reach of the joint search. The analysis method combines data from GW and HEN detectors, and uses the blue-luminosity-weighted distribution of galaxies. We derive expected GW+HEN source rate upper limits for a wide range of source parameters covering several emission models. Using published sensitivities of externally triggered searches, we derive joint upper limit estimates both for the ongoing analysis with the initial LIGO-Virgo GW detectors with the partial IceCube detector (22 strings) HEN detector and for projected results to advanced LIGO-Virgo detectors with the completed IceCube (86 strings). We discuss the constraints these upper limits impose on some existing GW+HEN emission models.

astro-ph.HE↗

arXiv2011

Bounding the Time Delay between High-energy Neutrinos and Gravitational-wave Transients from Gamma-ray Bursts

We derive a conservative coincidence time window for joint searches of gravita-tional-wave (GW) transients and high-energy neutrinos (HENs, with energies above 100GeV), emitted by gamma-ray bursts (GRBs). The last are among the most interesting astrophysical sources for coincident detections with current and near-future detectors. We take into account a broad range of emission mechanisms. We take the upper limit of GRB durations as the 95% quantile of the T90's of GRBs observed by BATSE, obtaining a GRB duration upper limit of ~150s. Using published results on high-energy (>100MeV) photon light curves for 8 GRBs detected by Fermi LAT, we verify that most high-energy photons are expected to be observed within the first ~150s of the GRB. Taking into account the breakout-time of the relativistic jet produced by the central engine, we allow GW and HEN emission to begin up to 100s before the onset of observable gamma photon production. Using published precursor time differences, we calculate a time upper bound for precursor activity, obtaining that 95% of precursors occur within ~250s prior to the onset of the GRB. Taking the above different processes into account, we arrive at a time window of tHEN - tGW ~ [-500s,+500s]. Considering the above processes, an upper bound can also be determined for the expected time window of GW and/or HEN signals coincident with a detected GRB, tGW - tGRB ~ tHEN - tGRB ~ [-350s,+150s].

astro-ph.HE↗

arXiv2010

The Antares Neutrino Telescope and Multi-Messenger Astronomy

Antares is currently the largest neutrino telescope operating in the Northern Hemisphere, aiming at the detection of high-energy neutrinos from astrophysical sources. Such observations would provide important clues about the processes at work in those sources, and possibly help solve the puzzle of ultra-high energy cosmic rays. In this context, Antares is developing several programs to improve its capabilities of revealing possible spatial and/or temporal correlations of neutrinos with other cosmic messengers: photons, cosmic rays and gravitational waves. The neutrino telescope and its most recent results are presented, together with these multi-messenger programs.

astro-ph.HE↗

arXiv2008

Antares/Virgo Coincidences : a feasibility study

Sources of gravitational waves (GW) and emitters of high energy (HE) neutrinos both involve compact objects and matter moving at relativistic speeds. Coincidences between Virgo and Antares would give a unique insight on the physics of the most powerful objects in the Universe. The feasibility of such GW/HE neutrino coincidences is analysed.

astro-ph↗

arXiv2008

Coincidences between Gravitational Wave Interferometers and High Energy Neutrino Telescopes

Sources of gravitational waves (GW) and emitters of high energy (HE) neutrinos both involve compact objects and matter moving at relativistic speeds. GW emission requires a departure from spherical symmetry, which is the case if clumps of matter are accreted around black holes or neutron stars, and ejected in relativistic jets, where neutrinos are believed to be produced. Both messengers interact weakly with the surrounding matter, hence point directly to the heart of the engines that power these emissions. Coincidences between GW interferometers (e.g. Virgo) and HE neutrino telescopes (e.g. Antares) would then give a unique insight on the physics of the most powerful objects in the Universe. The possibility, observability and detectability for such GW/HE neutrino coincidences are analysed.

astro-ph↗

arXiv2008

The ANTARES Neutrino Telescope: first results

The ANTARES Collaboration is completing the deployment of a 12 lines underwater detector, 2500m deep in the Mediterranean Sea, dedicated to high energy neutrino astronomy. Starting with the first line in 2006, 10 lines were continuously recording data by the end of 2007, which allow us to reconstruct downward-going cosmic muons, and search for the first upward-going neutrino-induced muons. Calibration topics will be described and preliminary results presented.

astro-ph↗

arXiv2004

ANTARES Status & Milestones : News from Deep-Sea

The ANTARES project aims to build a deep-sea Cherenkov Telescope for High Energy Neutrino Astronomy located in the Mediterranean Sea. The experiment, currently in the construction phase, has recently achieved an important milestone : the operation of a prototype line and of a line with monitoring instruments. These deployments allowed a thorough understanding of environmental parameters.

astro-ph↗

arXiv2003

Comparison of filters for detecting gravitational wave bursts in interferometric detectors

Filters developed in order to detect short bursts of gravitational waves in interferometric detector outputs are compared according to three main points. Conventional Receiver Operating Characteristics (ROC) are first built for all the considered filters and for three typical burst signals. Optimized ROC are shown for a simple pulse signal in order to estimate the best detection efficiency of the filters in the ideal case, while realistic ones obtained with filters working with several ``templates'' show how detection efficiencies can be degraded in a practical implementation. Secondly, estimations of biases and statistical errors on the reconstruction of the time of arrival of pulse-like signals are then given for each filter. Such results are crucial for future coincidence studies between Gravitational Wave detectors but also with neutrino or optical detectors. As most of the filters require a pre-whitening of the detector noise, the sensitivity to a non perfect noise whitening procedure is finally analysed. For this purpose lines of various frequencies and amplitudes are added to a Gaussian white noise and the outputs of the filters are studied in order to monitor the excess of false alarms induced by the lines. The comparison of the performances of the different filters finally show that they are complementary rather than competitive.

gr-qc↗

arXiv2001

Detection in coincidence of gravitational wave bursts with a network of interferometric detectors (I): Geometric acceptance and timing

Detecting gravitational wave bursts (characterised by short durations and poorly modelled waveforms) requires to have coincidences between several interferometric detectors in order to reject non-stationary noise events. As the wave amplitude seen in a detector depends on its location with respect to the source direction and as the signal to noise ratio of these bursts are expected to be low, coincidences between antennas may not be so likely. This paper investigates this question from a statistical point of view by using a simple model of a network of detectors; it also estimates the timing precision of a detection in an interferometer which is an important issue for the reconstruction of the source location, based on time delays.

gr-qc↗

arXiv2000

An efficient filter for detecting gravitational wave bursts in interferometric detectors

Typical sources of gravitational wave bursts are supernovae, for which no accurate models exist. This calls for search methods with high efficiency and robustness to be used in the data analysis of foreseen interferometric detectors. A set of such filters is designed to detect gravitational wave burst signals. We first present filters based on the linear fit of whitened data to short straight lines in a given time window and combine them in a non linear filter named ALF. We study the performances and efficiencies of these filters, with the help of a catalogue of simulated supernova signals. The ALF filter is the most performant and most efficient of all filters. Its performance reaches about 80% of the Optimal Filter performance designed for the same signals. Such a filter could be implemented as an online trigger (dedicated to detect bursts of unknown waveform) in interferometric detectors of gravitational waves.

gr-qc↗