Cinquième Assemblée Générale du GdR Ondes Gravitationnelles

11 oct. 2021, 12:00 → 12 oct. 2021, 17:00 Europe/Paris

LAPP - Laboratoire d'Annecy de Physique des Particules

Le GdR Ondes Gravitationnelles (http://gdrgw.in2p3.fr/) a été crée en 2017 avec le but de rassembler la communauté scientifique intéressée par l’exploration de l’Univers avec les ondes gravitationnelles, et de lui fournir des occasions de rencontres et de discussions communes. 

La cinquième assemblée générale du GdR Ondes Gravitationnelles se tiendra en présence au Laboratoire d'Annecy de Physique des Particules, et couvrira les thèmes d’intérêt du GdR, représentés par ses Groupes de Travail.

Cette assemblée sera la dernière assemblée générale de la première édition du GdR Ondes Gravitationnelles, puisque celui-ci arrivera à échéance en décembre. Nous encourageons vivement la participation en présence. L'événement sera retransmis, lien à suivre. 

Le pass sanitaire est requis pour participer à l'assemblée.

L'inscription à cette réunion est obligatoire avant le 12 septembre 2021. Il faut, au préalable, devenir membre du GdR en s'inscrivant sur le site http://gdrgw.in2p3.fr/

La date limite pour envoyer une contribution est le 2 septembre 2021.

        

 

 

 

 

 

lundi 11 octobre

Buffet d'accueil

Invited seminars

1 LIGO/Virgo O3 results

Orateur: Viola Sordini (IP2I Lyon)

AG_GdR_Annecy_O3latest_VSordini.pdf

2 New PTA results

Orateur: Stanislav Babak (APC)

PTA_GdR_short.pdf

Groupe de Travail: COSMOLOGIE

3 Recent advances in gravitational-wave cosmology

Standard sirens have been the central paradigm in gravitational-wave (GW)
cosmology so far. From the GW signature of compact star binaries, it is
possible to directly measure the luminosity distance of the source.
Since the source redshift cannot be inferred from the GW signal alone,
additional information is required for instance from the observation of
an electromagnetic counterpart. One of the lessons learned during the
last LIGO-Virgo science run O3 is that it may be more difficult than
expected to collect many electromagnetic counterparts of GW events in
the coming years. New techniques and ideas have emerged recently to
exploit another type of observables to obtain an estimate of the source
redshift.
In this talk, I will present an overview of those emerging techniques
along with recent results and future prospects associated to their
application.

I will first review the standard approach based on electromagnetic
observations, either the observation of a counterpart, e.g. a kilonova
transient or the use of galaxy surveys.
I will then turn to techniques that do not require electromagnetic
observations, such as neutron-star tidal deformability models, features
of the source-frame mass spectrum for compact binaries, angular
cross-correlation between galaxy and GW sources distributions, and
cross-correlation or identification of GWs lensing maps.

Orateur: Simone Mastrogiovanni (Astroparticule et cosmologie, Paris Diderot university)

gdr_5th_assembly (2).pdf

4 Cross-correlating galaxy catalogs and gravitational waves: a tomographic approach

Unveiling the origin of the coalescing binaries detected via gravitational waves (GW) is challenging, notably if no multi-wavelength counterpart is detected. One important diagnostic tool is the coalescing binary distribution with respect to the large scale structures (LSS) of the universe, which one can quantify via the cross-correlation of galaxy catalogs with GW ones.
I will present sensitivity prospects for the search of such a cross-correlation signal, by using both existing and forthcoming galaxy catalogs and using realistic Monte Carlo simulations of GW events. The cross-correlation signal should be marginally detectable in a 10-year data taking of advanced LIGO-Virgo detectors at design sensitivity, at least for binary neutron star mergers, while the expected addition of KAGRA and LIGO-India to the GW detector network would allow for a firmer detection of this signal and, in combination with future cosmological surveys, would also permit the detection of cross-correlation for coalescing black holes. I will show how adopting a tomographic approach as well as reaching a sufficiently accurate localization of GW events will be crucial to attain rather advanced model discrimination capabilities.

Orateur: Francesca Calore (LAPTh, CNRS)

gdrOG21_FCalore.pdf

5 Cosmology with Dark GW Sirens and the importance of population assumptions

Gravitational waves (GWs) from compact binary coalesces are cosmological standard sirens and provided with an electromagnetic (EM) counterpart can be used to probe cosmology. With the rapid increase of GW detector sensitivity, it will be less and less likely that GW sources are accompanied by an EM counterpart. Furthermore, the completeness of galaxy catalogs rapidly decreases and the statistical association of GW and EM data is less and less effective. We show how assumptions on the binary black hole formation channels that lead to features in the component mass distribution can be used to study GW-based cosmology. We discuss how those population assumptions can impact, and possibly lead to systematics on the inferred cosmology. This suggests to jointly infer population properties and cosmology. We show how this can be performed and what order of magnitude of the accuracy to expect for the up-coming science runs.

Orateur: Konstantin Leyde (APC Université de Paris)

presentation_dark_siren_analysis_gdr_gw_assemble_generale.pdf

6 Turbulent production of polarized gravitational radiation from primordial helical magnetic fields

The generation of primordial magnetic fields and its interaction with the primordial plasma during cosmological phase transitions is turbulent in nature. I will describe and discuss results of direct numerical simulations of magnetohydrodynamic (MHD) turbulence in the early universe and the resulting stochastic gravitational wave background (SGWB). In addition to the SGWB, the primordial magnetic field will evolve up to our present time and its relics can explain indirect observations of weak magnetic fields coherent on very large scales. I will apply the numerical results to magnetic fields produced at the electroweak and the QCD phase transitions and show that these signals may be detectable by the planned space-based Laser Interferometer Space Antenna (LISA) and by Pulsar Timing Array (PTA). The detection of these signals would lead to the understanding of the underlying physics of cosmological phase transitions, which can have consequences on the baryon asymmetry problem and on the origin seed of observed magnetic fields coherent over very large scales at the present time.
In particular, I will present the impact of helicity in primordial magnetic fields on the generation of a polarized GW background and the efforts to detect this polarization by using a network of space-based GW detectors, as LISA and Taiji. https://arxiv.org/abs/2107.05356.

Orateur: Alberto Roper Pol (APC)

GdR_nov21_ARP.pdf

Pause café

Groupe de Travail: COSMOLOGIE

7 Constraining higher-dimensional cosmology with gravitational wave standard sirens

The propagation of gravitational waves (GWs) at cosmological distances offers a new way to test the gravitational interaction at the largest scales. In this talk I will consider a homogeneous and isotropic cosmology with extra spatial dimensions at large scales, which represents a simple phenomenological prototype for extra-dimensional modified gravity cosmological models. By assuming that gravity propagates through the higher-dimensional spacetime, while photons are constrained to the usual four dimensions of general relativity, one can constrain the number of cosmological extra dimensions by using the relation between the luminosity distance measured by GW detectors and the one inferred by EM observations. After pointing out a redshift dependence in this relation which has been neglected in previous literature, I will present constraints obtained with the binary neutron star event GW170817 and forecasts for the Laser Interferometer Space Antenna (LISA) based on the simulation of multi-messenger observations of massive black hole binary (MBHB) mergers.

Orateur: Nicola Tamanini (L2I Toulouse, CNRS/IN2P3)

Tamanini_GdROGs_2021_Annecy.pdf

Groupe de Travail: Tests de la relativité générale et théories alternatives

8 Gravitational Waves in Scalar-Tensor Theory to one-and-a-half post-Newtonian order

We compute the gravitational waves generated by compact binary systems in a class of massless scalar-tensor (ST) theories to the 1.5 post-Newtonian order beyond the standard quadrupole radiation in general relativity (GR). Using (and adapting) the multipolar-post-Minkowskian and post-Newtonian formalism in GR we obtain in particular the tail and non-linear memory terms associated with the dipole radiation in ST theory. The multipole moments and GW flux are derived for general orbits and compared to previous results in the literature. In the case of quasi-circular orbits, we present ready-to-use templates for the data analysis of detectors.

Orateur: David Trestini (IAP et LUTH)

presentation_5eAG_GdR_Trestini.pdf

9 Search for spacetime symmetry breaking during gravitational waves propagation

It has been postulated that a unified theory of physics may break local Lorentz invariance and CPT symmetry. A general effective field theory predicts that such violation lead to anisotropic, polarization-dependent dispersion the gravitational waves during their propagation. Using a Bayesian inference analysis, we constrain the coefficients responsible of spacetime symmetry breaking with the second catalog of gravitational waves detected by LIGO and Virgo. We compare them with the expected design sensitivity of advanced LIGO and Virgo and discuss the degeneracies with the source parameters.

Orateur: Leïla Haegel (Laboratoire APC)

2021-10_11-gdr_gw_sme_haegel.pdf

10 Searching for scalars in spinning binaries

Light scalar fields that couple disformally to matter are a common feature in many alternative theories of gravity, such as in (beyond) Horndeski and general DHOST theories, in the decoupling limit of massive gravity, and in various brane-world scenarios. Exploring how well this kind of interaction is constrained by observational data thus provides valuable information for distinguishing between viable and unviable models. In this talk, I will describe recent work on the behaviour of binary systems that couple disformally to a light scalar field; focusing, in particular, on the effect of a disformal spin-orbit interaction. As it turns out, this interaction can dominate over the other spin-independent effects from the scalar in certain scenarios, and thus can be quite strongly constrained.

[Based on 2011.01213 and 2107.10841]

Orateur: Leong Khim Wong (IPhT, Université Paris-Saclay)

WONG_Leong_Khim.pdf

Groupe de Travail: Formes d'onde

11 Remodeling the Effective One-Body Formalism in Post-Minkowskian Gravity

Recent advances in the scattering amplitude-based approach to the Post-Minkowskian expansion of classical general relativity have demonstrated that this new approach holds the promise of significantly changing the efficiency of computations in general relativity. The results from the amplitude-based approach should be used to predict gravitational waveforms and other observables associated with two massive objects bound to each other. One strategy for going from the scattering regime to the bound-state regime is based on the Effective One-Body (EOB) formalism. In this context we provide a reformulation of the Effective One-Body Formalism that does not need non metric contributions, and we show how to fit all the know results from scattering up to the third post-Minkowskian order.

Orateur: Pierre Vanhove (IPhT CEA-Saclay)

ClassicalGravity-Annecy-octobre2021.pdf

12 Gravitational-wave mode (2,1) for a binary system of compact objects at the third post-Newtonian approximation

The post-Newtonian approximation is an essential ingredient in constructing
waveform templates for binary systems of compact objects to be used in data
analysis of gravitational-wave signals. The phases of such signals, in
particular, must be determined analytically with great accuracy in order to
reduce the biases that may arise in parameter estimation or when combining
analytic results with numerical relativity. The computation of the source
quadrupole moment of two point-like bodies at the third post-Newtonian (3PN)
order is an important step towards getting the targeted 4PN gravitational-wave
phase. This talk sketches the way it has been achieved by means of dimensional
regularisation combined with renormalisation. It is in fact a Hodge-type dual
of the current moment with the symmetry of some specific Young tableau that
has been generalised to d dimensions for this purpose. The final result is
used to construct the 3PN gravitational-wave mode (2,1).

Orateur: M. Guillaume Faye (I.A.P.)

Faye.pdf

13 Fast and accurate gravitational-wave modelling with principal component regression

Inference from gravitational-wave observations relies on the availability of accurate theoretical waveform models to compare with the data. This contribution considers the rapid generation of surrogate time-domain waveforms consistent with the gravitational-wave signature of the merger of spin-aligned binary black holes. Building on previous works, a machine-learning model is proposed that allows for highly-accurate waveform regression from a set of examples. An improvement of about an order of magnitude in accuracy with respect to the state of the art is demonstrated, along with a significant speed up in computing time with respect to the reference generation software tools.

Orateur: Cyril Cano (Gipsa-lab)

GdR_OG.pdf

Diner au buffet

mardi 12 octobre

Groupe de Travail: Population des sources

14 First detections of neutron star-black hole mergers

In this talk I will present the detection of NS-BH binary mergers with gravitational waves by the LIGO - Virgo- KAGRA collaboration. I will first present how the events GW200105 and GW200115 were detected: the first was observed by LIGO Livingston and Virgo, and the second
by all three LIGO–Virgo detectors. Then I will detail the main properties of the events and how we establish the presence of the NS.
These detections provide the first proof of the existence of this new class of binaries and I will present the inferred merger rate. Then I will place the merger rate and binary properties in the global context of known compact objects and the various formation channels of compact object mergers.

Orateur: Astrid Lamberts (Observatoire de la Côte d'Azur)

GDR_OG_Lamberts.pdf

15 Understanding the stellar progenitors of binary black holes

The black holes detected by the LVK gravitational wave detectors have masses (typically 20-50 Msun) that are systematically heavier than those detected in X-ray binaries (5-20 Msun). This mass discrepancy suggests different progenitor stellar environments, especially metallicity, between X-ray binary and gravitational wave black holes. We have built a model Universe that represents star formation for different redshift, host galaxy mass, stellar metallicity and in which we incorporate a binary evolution model under different conditions (stellar-wind, mass-transfer, Supernova). In this presentation, I will discuss preliminary results on our simulated binary black hole merger rates and binary evolution models that are consistent with the LVK population. Our analyses show that large black hole mergers are typically at redshift < 1, from dwarf galaxies with a low metallicity (0.02 Zsun) environment. However, most black hole systems arise at large redshifts(2-3), from Milky way mass galaxies in a high metallicity (<.9 Zsun) environment. The number of gravitational wave observations will increase in the following years and will further constrain the comparison. We will also extend our analyses to X-ray binaries in the Milky Way.

Orateur: Rahul Srinivasan (Universite Cote d'Azur)

GdR - Rahul Srinivasan.pdf

16 Source classification of compact binary mergers for the MBTA pipeline candidates

As the knowledge of the gravitational-wave (GW) sources population is improving, it is possible to compute the probability of astrophysical origin of the GW events and make a source classification.
Rapid source classification in low-latency searches provides useful information for astronomers to undertake a follow-up of the source or not.
In the offline searches, the probability of astrophysical origin of GW candidate events is a tool to reveal more events in population-rich areas of the parameter space. Also, the source classification is a key ingredient to compute compact binaries merger rates.
We present how the source classification of LIGO-Virgo GW candidate events is performed with the Multi-Band Template Analysis (MBTA), which is one of the pipelines used in the LIGO-Virgo searches. We discuss how we divide the search parameter space to be more sensitive to the astrophysical population priors that are not uniform across the parameter space and also to better estimate background rates over multiple bins. We also cover different systematic uncertainties on the probability of astrophysical origin related to the different assumptions we make in the computation (population models, number of detections, background fluctuations, etc...).

Orateur: Dimitri Estevez ({CNRS}UMR7178)

Source_classification_GdR_October_2021_final.pdf

17 Precession resonances in hierarchical triple systems

A binary system can be resonantly excited by a distant perturber if its precession frequency is equal to the period of the faraway object. I will show how this can dramatically increase the eccentricity of the binary, pushing it to values observables in the LISA band. This phenomenon is new and distinct from the Kozai-Lidov mechanism since it operates in a corner of the parameter space where current studies assume that the state of the binary is unaffected by the perturber.

Orateur: Adrien Kuntz (Scuola Normale Superiore)

Precession resonances in hierarchical triple systems

18 Constraints to neutron-star kicks in High-Mass X-ray Binaries with Gaia EDR3

All neutron star progenitors in neutron-star High-Mass X-ray Binaries (NS HMXBs) undergo a supernova event that may lead to a significant natal kick impacting the motion of the whole binary system. The space observatory Gaia performs a deep optical survey with exquisite astrometric accuracy, for both position and proper motions, that can be used to study natal kicks in NS HMXBs.

We aim to survey the observed Galactic NS HMXB population and to quantify the magnitude of the kick imparted onto their NSs, and to highlight any possible differences arising in between the various HMXB types.

We perform a census of Galactic NS HMXBs and cross-match existing detections in X-rays, optical and infrared with the Gaia Early Data Release 3 database. After retrieving their parallaxes, proper motions, and radial velocities (when available), we compute their peculiar velocities with respect to the rotating reference frame of the Milky Way, and including their respective masses and periods, we estimate their kick velocities through Markov Chain Monte Carlo simulations of the orbit undergoing a supernova event.

We infer the posterior kick distributions of 35 NS HMXBs. After an inconclusive attempt at characterizing the kick distributions with Maxwellian statistics, we find that the observed NS kicks are best reproduced by a Gamma distribution of mean $116^{+18}_{-15}$ km s$^{-1}$. We note that supergiant systems tend to have higher kick velocities than Be High-Mass X-ray Binaries. The peculiar velocity versus non-degenerate companion mass plane hints at a similar trend, supergiant systems having a higher peculiar velocity independently of their mass.

Orateur: Francis Fortin (APC)

2021-10-12_GdROG_Gaia_kicks.pdf

Groupe de Travail: prédiction et suivi des signaux multi-messager

19 Electromagnetic counterparts of binary neutron star mergers: perspectives for future detections & multi-messenger studies

In this talk, we will present recent results obtained with our population model for the future detectability of electromagnetic counterparts of BNS mergers (kilonova, afterglow, short gamma-ray burst). We will also give examples of multi-messenger studies that can be conducted using these future detections.

Orateur: Prof. Frédéric Daigne (IAP)

20211012-Daigne.pdf

Pause café

Discussion sur la prochaine édition du GDR

GDR-Annecy.pdf

Déjeuner au buffet

Groupe de Travail: Etoiles à neutrons, supernovae et synthèse des éléments lourds

20 Gravitational waves from core-collapse supernovae with strong rotation and magnetic fields

Core-collapse supernovae (CCSN) are an important formation channel for astrophysical compact objects that release huge quantities of gravitational binding energy in the form of neutrino emission, energetic ejecta and gravitational waves (GW).
The latter represent an extraordinary tool to probe the properties of the forming proto-neutron star (PNS), such as its mass and radius, and the characteristics of the convective motions occurring within it. Multi-dimensional numerical simulations are therefore a fundamental instrument to investigate the complexity of the GW emission and deduce the physical properties of the system from the observed signal.
I will briefly present our current understanding of the numerical modeling of GW emission from CCSN with a particular focus on the impact of rapid rotation, showing the connection between the onset of corotational instabilities within the PNS and the emission of strong gravitational signals.
I will then show some preliminary results that take into account the presence of magnetic fields and their effect on both the PNS dynamics and the related multi-messanger emission.

Orateur: Dr Matteo Bugli (CEA - Saclay)

GdR_OG_2021_Bugli.pdf

21 Maximum mass of compact stars from gravitational wave events with finite-temperature equations of state

In this talk, I will discuss relations between global parameters of hot and fast-rotating compact stars which do not depend on the equation of state, including a relation connecting the masses of the mass-shedding (Kepler) and static configurations. These relations will then be applied to the GW170817 event by adopting the scenario in which a hypermassive compact star remnant formed in a merger evolves into a supramassive compact star that collapses into a black hole once the stability line for such stars is crossed. An upper limit is deduced on the maximum mass of static, cold neutron stars for the typical range of entropy per baryon and electron fraction characterizing the hot hypermassive star. Our result implies that accounting for the finite temperature of the merger remnant relaxes previously derived constraints on the value of the maximum mass of a cold, static compact star.

Orateur: Micaela Oertel (LUTH, Observatoire de Paris)

oertel.pdf

22 The use of non-unified equations of state and its consequence on the modelisation of macroscopic parameters of Neutron Stars

The observation of macroscopic features can help us investigate matter of Neutron Stars's deepest layers in conditions of density that cannot be reproduced on Earth. The bridge between dense matter physics and Neutron Star observation is provided by the modelisation of macroscopic parameters such as the mass, the radius or the tidal deformability via relativistic equations of hydrodynamics. A common practice within the astronuclear physicist community is to construct nuclear models for Neutron Star interior separately for the crust (lattice) and the core (homogeneous matter) and then gluing both regions to construct an equation of state for the whole star. Using a nuclear model that has not been calculated consistently for the core and the crust, can result in artificial errors that can surpass the observation precision of current and next generation detectors. We propose to expose the importance of using unified equations of state and to understand why errors appear on the microscopic level to reverberate on the macroscopic scale. The role of non-unified equations of state in analytical representation as well as "universal" relations is also investigated.

Orateur: Mlle Lami Suleiman (Laboratoire Univers et Théories)

SuleimanGDR.pdf

23 Dense matter equation of state with improved nuclear physics

I will present a new model for dense matter which combines the knowledge of recent theory predictions from chiral EFT, experimental nuclear masses and astrophysical constrains to construct unified equations of state (EoS) describing dense matter in neutron stars (NS), from the crust to the dense core. Based on a recent meta-model for the nuclear component, it allows us to describe the matter component in terms of neutrons, protons, electrons, muons, as well as phase transitions at high density. A set controlled meta-models are confronted to a representative phenomenological force (SLy4). We show that some crust properties, e.g., energy per particle, pressure, sound speed, are mostly influenced by low-density predictions in neutron matter, where chiral EFT and phenomenological forces substantially differ. Other properties of the crust, e.g. clusters mass, charge, and asymmetry, are mostly determined by symmetric matter properties close to saturation density and are therefore mainly constrained by experimental nuclear masses. Finally, by solving the TOV equations we analyze NS mass-radius relations and tidal deformability, which can be confronted to GW observations.

Orateur: Dr Guilherme Grams (ip2i)

GGrams_presentation_GdR_OG.pdf

Groupe de Travail: Méthodes d'analyse des données

24 Fast Parameter Estimationfor Massive Black Hole Binaries with Invertable Flows

One of the sources which Laser Interferometer Space Antenna (LISA) will observe are the signals from the Massive Black Hole Binaries (MBHBs) during their inspiral, merged and ringdown phases. To estimate physical parameters of these systems and their localisations one has to perform some form of Bayesian Inference. The most common approach to do this is through defining the likelihood function and producing posterior samples with some form of sampling technique. The disadvantage of the sampling methods is that they are slow. We propose the Bayesian parameter estimation method which is based on the Normalising flows a technique which allows to make an extremely fast mapping from the base sample distribution to the posterior conditioned on the data. This is implemented by learning this mapping in advance on the training dataset and then applying the trained map to the real data. We apply this method to the data from the first LISA Data Challenge (LDC) in order to evaluate how the estimated posteriors agree with the standard approaches. The main purpose of the fast parameter estimation is to use it for the multi-messenger observations and to be able to alert other observatories to perform follow-ups.

Orateur: Natalia Korsakova (SYRTE/Observatoire de Paris)

FastPE_NataliaKorsakova_GdR.pdf

25 Learning-based representation of gravitational wave signals for LISA data analysis

We investigate a new method for the fast recovery of gravitational wave (GW) signals drowned in noise relevant to LISA physics. For that purpose, we describe an original learning based non-parametric reconstruction of the imprint of GW sources in measurements affected by instrumental noise. We evaluate its performances on the case of galactic binary (GB) signals.
The proposed approach builds upon a projection of the interferometric measurements on a manifold of plausible signals. This manifold encodes an adapted representation of GB waveforms, which is learnt with a manifold-learning algorithm coined Interpolatory Auto Encoder.
We will explain the concept of the algorithm and show promising preliminary applications on single binary sources.

Orateur: Aurore Blelly (CEA-IRFU)

BLELLY_GdR_OG_2021_10_12.pdf

26 Sky localization and parameter estimation of massive black hole mergers with LISA

The future space-based instrument LISA will open a new window to low-frequency gravitational wave signals. In particular, it will detect mergers of massive black hole binaries (MBHB) with high signal-to-noise ratios, enabling unprecedented scientific applications, like multimessenger observations with instruments such as Athena, LSST and SKA, and the use of these joint detections as standard sirens. Understanding the capability of LISA to localize these MBHB signals in the sky, both during their inspiral and after coalescence, is crucial for these applications. Using accelerated Bayesian inference tools that allow to go beyond Fisher-matrix based estimates, we survey LISA's abilities in terms of parameter recovery. We confirm the crucial role of higher harmonics in the signal and identify the respective roles of the time- and frequency-dependencies in the instrumental response in breaking degeneracies in parameter space. We discuss in particular LISA's ability to localize a binary in advance of the merger, and the occurence of multimodalities in the posterior distribution for the sky position.

Orateur: Sylvain MARSAT ({CNRS}UMR7164)

gdr_marsat_2021-10-13.pdf

27 Rapid Identification of continuous gravitational-wave signals

Continuous gravitational waves (CWs) from asymmetric spinning neutron stars are among the most interesting, although still undetected, targets of the Advanced LIGO-Virgo detectors. The search for this class of signals is difficult due to their expected weakness, and can be very computationally expensive when the source parameters are not known.
The stochastic group uses fast and consolidated cross-correlation techniques to search for either a stochastic background of gravitational waves (SGWB) or persistent gravitational waves in specific directions. Recent investigations have shown that stochastic directional searches have the ability to detect CWs as well, with less sensitivity than CWs searches, but with low computing requirements.
We present a joint SGWB-CW pipeline chain that uses the robustness of SGWB cross-correlation algorithms to quickly identify CW signals, and the accuracy of CW matched-filtering-based codes to properly follow up interesting CW candidates.

Orateur: Iuri La Rosa (LAPP, Virgo)

GdR 5 - Iuri La Rosa.pdf

Pause café

Groupe de Travail: détecteurs

28 Status of the Virgo commissioning: on the path towards the O4 run

Since 2020, the Virgo interferometer has entered the phase 1 of the Advanced Virgo + project, which consists in a series of detector upgrades aiming at improving the Virgo sensitivity by up to a factor 2 for the next data taking run foreseen to start in fall 2022. Following the installation works that took part mostly in 2020, the commissioning phase started in January 2021, with multiple challenges: controlling the interferometer in its new optical configuration (dual recycled interferometer) and with an increased input power, commissioning the new frequency dependent squeezing system, and hunting the technical noises limiting the interferometer sensitivity. An overview of the status of the works previously mentioned will be given in this talk.

Orateur: Romain Gouaty (CNRS, LAPP - UMR5814)

Status of the Virgo commissioning.pdf

29 Development of a crystalline mirror by transfer of a AlGaAs/GaAs multilayer coating on a silica substrate

Reducing thermal noise in mirror's coating is one of the main challenge in the noise hunting field whithin gravitational waves detectors.
Focus has been made on new materials that have better mechanical properties and thus lower thermal noises. I have worked in my PhD thesis work on the development of a Bragg mirror by transferring a AlGaAs/GaAs crystalline coating from a GaAs substrate to a SiO2 substrate. The experimental work has been conducted with CEA LETI at Grenoble. I will present the main technological issues that we encountered and the key results that we obtained.

Orateur: Victor Hui (LAPP)

Présentation GdR OG Octobre 2021_final.pdf

30 LISA Dynamics & Control: DFACS Simulation and Optimization, Noise assessment and Data processing

LISA detection principle and sensitivity relies strongly on successful suppression of spacecraft dynamical jitter noise trough post-processing data combination (TDI, INREP). However residuals due to cross-couplings are expected to be important entries to the current noise budget, and in general, post-processing suppression of spacecraft stray motions have not yet been subject to numerous numerical studies & optimizations. In this talk we present a first implementation of the Dynamics of LISA spacecraft and test masses within the current end-to-end simulation of LISA. It allows demonstrating numerically the full suppression of spacecraft jitter when cross-couplings are deactivated, as well as, will provide quantitative estimates for the residual spacecraft jitters potentially leaking to the science channel. In addition, we discuss an optimization strategy for the DFACS which participates to the mitigation of such couplings. This last work have also inspired possible data combinations for local, independent measurements of test mass acceleration noise, hence providing precious information for data processing and analysis.

Orateur: Henri INCHAUSPÉ (Laboratoire APC - Université Paris Diderot)

LISA DFACS.pdf