Advanced Virgo: Status of the Detector, Latest Results and Future Prospects

none6noopenBersanetti, Diego; Patricelli, Barbara; Piccinni, Ornella Juliana; Piergiovanni, Francesco; Salemi, Francesco; Sequino, ValeriaBersanetti, Diego; Patricelli, Barbara; Piccinni, Ornella Juliana; Piergiovanni, Francesco; Salemi, Francesco; Sequino, Valeri

Measurement of gravitational and thermal effects in a liquid-actuated torsion pendulum

We describe a proof-of-principle experiment aiming to investigate the inverse-square law of gravitation at the centimeter scale. The sensor is a two-stage torsion pendulum, while actuation is accomplished by a variable liquid mass. The time-varying gravitational force is related to the level of the circulating fluid in one or two containers at a short distance from the test mass, with all moving mechanical parts positioned at a large distance. We provide a description of the apparatus and present the first results. We identified a systematic effect of thermal origin, producing offsets of few fNm in torque and of about 10 pN in force. When this effect is neutralized, the measurements agree well with the predictions of simulations. We also discuss the upcoming instrument upgradations and the expected sensitivity improvement that will allow us to perform measurements with adequate accuracy to investigate the unexplored regions of the α−λ parameter space of a Yukawa-like deviation from the Newtonian potential

Quantum Backaction on kg-Scale Mirrors: Observation of Radiation Pressure Noise in the Advanced Virgo Detector

The quantum radiation pressure and the quantum shot noise in laser-interferometric gravitational wave detectors constitute a macroscopic manifestation of the Heisenberg inequality. If quantum shot noise can be easily observed, the observation of quantum radiation pressure noise has been elusive, so far, due to the technical noise competing with quantum effects. Here, we discuss the evidence of quantum radiation pressure noise in the Advanced Virgo gravitational wave detector. In our experiment, we inject squeezed vacuum states of light into the interferometer in order to manipulate the quantum backaction on the 42 kg mirrors and observe the corresponding quantum noise driven displacement at frequencies between 30 and 70 Hz. The experimental data, obtained in various interferometer configurations, is tested against the Advanced Virgo detector quantum noise model which confirmed the measured magnitude of quantum radiation pressure noise

Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)

This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands

The population of merging compact binaries inferred using gravitational waves through GWTC-3

We report on the population properties of 76 compact binary mergers detected with gravitational waves below a false alarm rate of 1 per year through GWTC-3. The catalog contains three classes of binary mergers: BBH, BNS, and NSBH mergers. We infer the BNS merger rate to be between 10 $\rm{Gpc^{-3} yr^{-1}}$ and 1700 $\rm{Gpc^{-3} yr^{-1}}$ and the NSBH merger rate to be between 7.8 $\rm{Gpc^{-3}\, yr^{-1}}$ and 140 $\rm{Gpc^{-3} yr^{-1}}$ , assuming a constant rate density versus comoving volume and taking the union of 90% credible intervals for methods used in this work. Accounting for the BBH merger rate to evolve with redshift, we find the BBH merger rate to be between 17.9 $\rm{Gpc^{-3}\, yr^{-1}}$ and 44 $\rm{Gpc^{-3}\, yr^{-1}}$ at a fiducial redshift (z=0.2). We obtain a broad neutron star mass distribution extending from $1.2^{+0.1}_{-0.2} M_\odot$ to $2.0^{+0.3}_{-0.3} M_\odot$. We can confidently identify a rapid decrease in merger rate versus component mass between neutron star-like masses and black-hole-like masses, but there is no evidence that the merger rate increases again before 10 $M_\odot$. We also find the BBH mass distribution has localized over- and under-densities relative to a power law distribution. While we continue to find the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above $\sim 60 M_\odot$. The rate of BBH mergers is observed to increase with redshift at a rate proportional to $(1+z)^{\kappa}$ with $\kappa = 2.9^{+1.7}_{-1.8}$ for $z\lesssim 1$. Observed black hole spins are small, with half of spin magnitudes below $\chi_i \simeq 0.25$. We observe evidence of negative aligned spins in the population, and an increase in spin magnitude for systems with more unequal mass ratio

5n-vector ensemble method for detecting gravitational waves from known pulsars

We present a multiple test for the targeted search of continuous gravitational waves from an ensemble of known pulsars, combining multidetector single pulsar statistics defined through the 5n-vector method. In order to maximize the detection probability, we describe a rank truncation method to select the most promising sources within the ensemble, based on the p-values computed for single pulsar analysis. To test the efficiency of our method, we use a Monte Carlo procedure and define a p-value for the ensemble that is an overall p-value for the hypothesis of continuous wave emissions from a set of known pulsars. We also perform a pilot search on real data from the O3A dataset of the two LIGO detectors

Adaptive optics methods in gravitational wave interferometric detectors, a perspective

The performance of present and future gravitational wave detectors is limited by fundamental factors, such as thermal noise, seismic or newtonian noise and quantum nature of light. Besides, technological factors impact the reach of advanced detectors in that upgrade strategies are limited by state-of-art performances. In the realm of optics, the quantum limit to sensitivity will be addressed by injecting higher laser power and by exploiting the capabilities of squeezed light. In turn, technological efforts in the preparation of suitable optics able to meet more and more demandig requirements are ongoing. Moreover, solutions to mitigate the effect of known showstoppers such as parametric instablities are being studied. The present day strategy to correct for residual cold defects in the core optics and to counteract the thermal effects due to power absorption is embedded in a set of sensors and actuators integrated in the Advanced Virgo design, the so called Thermal Compensation System (TCS). This system is designed to be focused on the needs of high power operation of the detector, nonetheless it is highly versatile and can deal with foreseen and unexpected issues. We discuss the features of the TCS with emphasis on its versatility and portability to upgraded detectors; we also present the status of the R&D activity in the Tor Vergata labs, highlighting new applications where the methods of TCS can have a relevant impact, such as adaptive mode matching for squeezing and damping of parametric instabilities

Finite state machine controls for a source of optical squeezed vacuum

In this paper we present a software, developed in the distributed control system environment of the Virgo gravitational-wave detector, for the management of a highly automated optical bench. The bench is extensively used for the research and development of squeezed states of light generation in order to mitigate the quantum noise in the next generations of interferometric gravitational-wave detectors. The software is developed using Finite-State Machines, recently implemented as a new feature of damping-adv Software Development Kit. It has been studied for its ease of use and stability of operation and thus offers a high duty-cycle of operation. Much attention has been drawn to ensure the software scalability and integration with the existing Data AcQuisition and control infrastructure of the Virgo detector

Electronic hardware and software development for the Advanced Virgo EPR squeezer

In this paper, we introduce the work on hardware and software built to manage the optical bench which hosts the optical squeezer source at the Virgo site in Cascina. In the past, the ex-perimental setup implemented frequency-independent squeezing and it will be soon recon gured in order to implement frequency-dependent squeezing via EPR entanglement for Virgo gravitational-wave detector. Furthermore we introduce an idea of automation for this prototypic subsystem in order to deliver a compact and robust apparatus which does not require surveillance of an operator