Jump to content

Virgo interferometer

Coordinates: 43°37′53″N 10°30′16″E / 43.6313°N 10.5045°E / 43.6313; 10.5045
From Wikipedia, the free encyclopedia
(Redirected from VIRGO (physics))

The Virgo experiment
Formation1993
TypeInternational scientific collaboration
PurposeGravitational wave detection
HeadquartersEuropean Gravitational Observatory
Location
Coordinates43°37′53″N 10°30′16″E / 43.6313°N 10.5045°E / 43.6313; 10.5045
Region
Italy
FieldsBasic research
Spokesperson
Gianluca Gemme
AffiliationsLVK (LIGO-Virgo-KAGRA collaboration)
Budget
About ten million euros per year
StaffAround 880 people participate in the Virgo Collaboration
Websitewww.virgo-gw.eu
For broader coverage of detectors like Virgo, see Ground-based interferometric gravitational-wave search.

The Virgo interferometer is a large-scale experiment for detecting gravitational waves. It is in Santo Stefano a Macerata, near the city of Pisa, Italy. The instrument –a Michelson interferometer – has two arms that are 3 kilometres (1.9 mi) long and contain its mirrors and instrumentation in an ultra-high vacuum.

Virgo is hosted by the European Gravitational Observatory (EGO), a consortium founded by the French Centre National de la Recherche Scientifique (CNRS) and the Italian Istituto Nazionale di Fisica Nucleare (INFN).[1] The Virgo Collaboration operates the detector, and defines the strategy and policy for its use and upgrades. The collaboration consists of more than 850 members in 16 countries.[2] The Virgo interferometer works in collaboration with other similar detectors, including the two LIGO interferometers in the United States (at the Hanford Site and in Livingston, Louisiana) and the Japanese interferometer KAGRA (in the Kamioka mine). Cooperation between several detectors is crucial for detecting gravitational waves and pinpointing their origin; the LIGO and Virgo collaborations have shared their data since 2007, and with KAGRA since 2019, to form the LIGO-Virgo-KAGRA (LVK) collaboration.[3]

The interferometer is named after the Virgo Cluster, a cluster of about 1,500 galaxies in the Virgo constellation about 50 million light-years from Earth.[4] It was conceived and built when gravitational waves were only a prediction of general relativity; the project was first approved in 1992 and the construction was completed in 2003. After several years of improvements without detection, it was shut down in 2011 for the "Advanced Virgo" upgrades. In 2015, the first observation of gravitational waves was made by the two LIGO detectors, while Virgo was still being upgraded. It resumed observations in early August 2017, making its first detection on August 14 (together with the LIGO detectors); this was quickly followed by the detection of the GW170817 gravitational wave, the only one observed with classical methods (optical, gamma-ray, X-ray and radio telescopes) as of 2024.[5] The detector is used for joint observing runs with the other detectors, separated by commissioning periods during which it is upgraded to increase its sensitivity and scientific output.[6]

  Country with institutions contributing to EGO and the Virgo Collaboration as of 2021
  Country with institutions contributing to the Virgo Collaboration as of 2021

Organization

[edit]

The Virgo experiment is managed by the European Gravitational Observatory (EGO) consortium, which was created in December 2000 by the French National Centre for Scientific Research (CNRS) and the Istituto Nazionale di Fisica Nucleare (INFN).[7] Nikhef, the Dutch Institute for Nuclear and High-Energy Physics, later joined as an observer and eventually became a full member. EGO is responsible for the Virgo site and is in charge of the construction, maintenance, and operation of the detector and its upgrades. One of EGO's goals is to promote research on, and studies of, gravity in Europe.[1] The budget of EGO is around 10 million euros per year, employing around 60 people.[8]

The Virgo Collaboration consists of all the researchers working on various aspects of the detector. About 880 members, representing 182 institutions in 21 countries, were part of the collaboration in October 2024.[9][10] This includes institutions in France, Italy, the Netherlands, Poland, Spain, Belgium, Germany, Hungary, Portugal, Greece, Czechia, Denmark, Ireland, Monaco, Switzerland, Brazil, Burkina Faso, China, Israel, Japan and South Korea.[10]

The Virgo Collaboration is part of the larger LIGO-Virgo-KAGRA (LVK) Collaboration, which gathers scientists from the other major gravitational-waves experiments to jointly analyze the data; this is crucial for gravitational-wave detection.[11][12] LVK began in 2007[3] as the LIGO-Virgo Collaboration, and was expanded when KAGRA joined in 2019.[13][14]

Science case

[edit]
A color image
Computer simulation of gravitational waves emitted by the orbital decay and merger of two black holes
Visual representation of a signal which increases in frequency
Typical "chirp" of a gravitational-wave signal from the GW170817 event. The x axis represents time, and the y axis the frequency. The frequency increase over time is typical of gravitational waves from binary compact objects, and its shape is primarily determined by the objects' mass.[15]
Main article: Ground-based interferometric gravitational-wave search § Science case

Virgo is designed to look for gravitational waves emitted by astrophysical sources across the universe which can be classified into three types:[16]

  • Transient sources, which are objects only detectable for a short period. The main sources in this category are compact binary coalescenses (CBC) from binary black holes (or neutron stars) merging, emitting a rapidly-growing signal which only becomes detectable in the last seconds before the merger. Other possible sources of short-lived gravitational waves are supernovas, instabilities in compact systems, or exotic sources such as cosmic strings.
  • Continuous sources, emitting a signal observable on a long time scale. Prime candidates are rapidly-spinning neutron stars (pulsars), which may emit gravitational waves if they are not perfectly spherical (e.g. if there are tiny "mountains" on the surface).
  • Stochastic backgrounds, a type of generally-continuous signal diffused across large regions of the sky rather than from a single source. It could consist of a large number of indistinguishable sources from the above categories, or originate from the early moments of the universe.

Detection of these sources is a new way to observe them (often with different information than classical methods such as telescopes) and to probe fundamental properties of gravity such as the polarization of gravitational waves,[17] possible gravitational lensing,[18] or determining whether the observed signals are correctly described by general relativity.[19] It also provides a way to measure the Hubble constant.[20]

Instrument

[edit]

Principle

[edit]
Main article: Ground-based interferometric gravitational-wave search § Principle
White buildings and two long, blue pipes
2015 aerial view of the Virgo site's central building, the Mode-Cleaner building, the 3-km-long (1.9 mi) west arm and the beginning of the north arm (right). Other buildings include offices, workshops, the local computing center and the interferometer control room.
Animation of gravitational-wave detection with an interferometer such as Virgo. Mirror displacements and phase difference are exaggerated, and time is slowed by more than a factor of 10.[21]

In general relativity, a gravitational wave is a space-time perturbation which propagates at the speed of light. It slightly curves spacetime, changing the light path. This can be detected with a Michelson interferometer, in which a laser is divided into two beams travelling in orthogonal directions, bouncing on a mirror at the end of each arm. As the gravitational wave passes, it alters the path of the two beams differently; they are then recombined, and the resulting interferometric pattern is measured with a photodiode. Since the induced deformation is extremely small, precision in mirror position, laser stability, measurements, and isolation from outside noise are essential.[22]

Laser and injection system

[edit]
Another schematic diagram
Layout of the Virgo interferometer during the O4 run (2023-2024), including the signal-recycling mirror and filter cavity absent from the previous run. Laser power estimates are indicative.[23]

The laser, the experiment's light source, must be powerful and stable in frequency and amplitude.[24] To meet these specifications, the beam starts from a low-power, stable laser.[25] Light from the laser passes through several amplifiers, which enhance its power by a factor of 100. A 50 watt (W) output power was achieved for the last configuration of the initial Virgo detector (reaching 100 W during the O3 run after the Advanced Virgo upgrades), and is expected to be upgraded to 130 W at the beginning of the O4 run.[23] The original Virgo detector had a master-slave laser system, where a "master" laser is used to stabilize a high-powered "slave" laser; the master laser was a Nd:YAG laser, and the slave laser was a Nd:YVO4 laser.[26] The solution for Advanced Virgo is to have a fiber laser, with an amplification stage also made of fibers, to improve the system's robustness; its final configuration is planned to combine the light of two lasers to reach the required power.[27][28] The laser's wavelength is 1064 nanometres in the original and Advanced Virgo configurations.[23]

This laser is sent into the interferometer after passing through the injection system, which ensures the stability of the beam, adjusts its shape and power, and positions it correctly for entering the interferometer. The injection system includes the input mode cleaner, which is a 140-metre-long (460 ft) cavity designed to improve beam quality by stabilizing the frequency, removing unwanted light propagation and reducing the effect of laser misalignment. It also features a Faraday isolator preventing light from returning to the laser, and a mode-matching telescope which adapts the size and position of the beam before it enters the interferometer.[27]

Mirrors

[edit]
A round mirror
Mirror from the initial Virgo detector, now an exposition model at the Virgo site

The large mirrors in each arm are the interferometer's most critical optics. They include the two end mirrors at the ends of the 3-km (1.9 mi) interferometer arms and the two input mirrors near the beginning of the arms. These mirrors make a resonant optical cavity in each arm in which the light bounces thousands of times before returning to the beam splitter, maximizing the signal's effect on the laser path[29] and allowing the power of the light circulating in the arms to be increased. These mirrors (designed for Virgo) are cylinders 35 cm (14 in) in diameter and 20 cm (7.9 in) thick,[27] made from the purest glass obtainable.[30] The mirrors are polished to the atomic level to avoid diffusing (and losing) any light.[31] A reflective coating (a Bragg reflector made with ion-beam sputtering) is then added. The mirrors at the end of the arms reflect almost all incoming light, with less than 0.002 percent lost at each reflection.[32]

Two other mirrors are also in the final design:

  • The power-recycling mirror, between the laser and the beam splitter. Since most light is reflected toward the laser after returning to the beam splitter, this mirror re-injects the light into the main interferometer and increases power in the arms.
  • The signal-recycling mirror, at the interferometer output, re-injects part of the signal into the interferometer (transmission of this mirror is planned to be 40 percent) and forms another cavity. With small adjustments to this mirror, quantum noise can be reduced in part of the frequency band and increased elsewhere; this makes it possible to tune the interferometer for certain frequencies. It is planned to use a wideband configuration, decreasing noise at high and low frequencies and increasing it at intermediate frequencies. Decreased noise at high frequencies is of particular interest for study of a signal right before and after a compact object merger.[23][33]

Superattenuators

[edit]
Diagram of a superattenuator
A Virgo mirror is supported in a vacuum by a superattenuator, which dampens seismic vibrations. It is a chain of pendula hanging from an upper platform and supported by three legs clamped to ground, forming an inverted pendulum.[34] Seismic vibrations above 10 Hz are reduced by over 1012 times,[35] and the mirror position is controlled.

To mitigate seismic noise which could propagate up to the mirrors, shaking them and obscuring potential gravitational-wave signals, the mirrors are suspended by a complex system. The main mirrors are suspended by four thin fibers made of silica[36] which are attached to a series of attenuators. This superattenuator, nearly 8 metres (26 ft) high, is in a vacuum.[37] The superattenuators limit disturbances to the mirrors and allow mirror position and orientation to be precisely steered. The optical table with the injection optics used to shape the laser beam, such as the benches used for the light detection, are also suspended in a vacuum to limit seismic and acoustic noise. In the Advanced Virgo configuration, the instrumentation used to detect gravitational-wave signals and steer the interferometer (photodiodes, cameras, and associated electronics) is installed on several benches suspended in a vacuum.[27]

Superattenuator design is based on passive attenuation of seismic noise achieved by chaining several pendula, each a harmonic oscillator. They have a resonant frequency (diminishing with pendulum length) above which noise will be dampened; chaining several pendula reduces noise by twelve orders of magnitude, introducing resonant frequencies which are higher than a single long pendulum.[38] The highest resonant frequency is around 2 Hz, providing meaningful noise reduction starting at 4 Hz[27] and reaching the level needed to detect gravitational waves around 10 Hz. The system is limited in that noise in the resonant-frequency band (below 2 Hz) is not filtered and can generate large oscillations; this is mitigated by an active damping system, including sensors measuring seismic noise and actuators controlling the superattenuator to counteract the noise.[38]

Detection system

[edit]

Part of the light in the arm cavities is sent towards the detection system by the beam splitter. The interferometer works near the "dark fringe", with very little light sent towards the output; most is sent back to the input, to be collected by the power-recycling mirror. A fraction of this light is reflected back by the signal-recycling mirror, and the rest is collected by the detection system. It first passes through the output mode cleaner, which filters the "high-order modes" (light propagating in an unwanted way, typically from small defects in the mirrors)[39] before reaching the photodiodes which measure the light intensity. The output mode cleaner and the photodiodes are suspended in a vacuum.[40]

Intricate optics, with a person nearby for scale
Detection bench of the Virgo interferometer before its April 2015 installation. It is 88 cm wide and hosts the output mode cleaner; the photodiode is on another bench.[41]

With the O3 run, a squeezed vacuum source was introduced to reduce the quantum noise which is one of the main limitations to sensitivity. When replacing the standard vacuum with a squeezed vacuum, the fluctuations of a quantity are decreased at the expense of increasing the fluctuations of the other quantity due to Heisenberg's uncertainty principle. In Virgo, the quantities are the amplitude and phase of the light. A squeezed vacuum was proposed in 1981 by Carlton Caves during the infancy of gravitational-wave detectors.[42] During the O3 run, frequency-independent squeezing was implemented; squeezing is identical at all frequencies, reducing shot noise (dominant at high frequencies) and increasing radiation pressure noise (dominant at low frequencies, and not limiting the instrument's sensitivity).[43] Due to the addition of the squeezed vacuum injection, quantum noise was reduced by 3.2 dB at high frequencies and the detector's range was increased by five to eight percent.[44] More sophisticated squeezed states are produced[45] by combining the technology from O3 with a new 285-m-long (935 ft) filter cavity. This technology, known as frequency-dependent squeezing, helps to reduce shot noise at high frequencies (where radiation pressure noise is irrelevant) and reduce radiation-pressure noise at low frequencies (where shot noise is low).[46][47]

Infrastructure

[edit]

From the air, the Virgo detector has an "L" shape with its two 3-km-long (1.9 mi) perpendicular arms. The arm "tunnels" house pipes in which the laser beams travel in a vacuum. Virgo is Europe's largest ultra-high vacuum installation, with a volume of 6,800 cubic meters.[48] The two 3-km (1.9 mi) arms are made of a long steel pipe 1.2 m (3.9 ft) in diameter, in which the target residual pressure is about one-thousandth of a billionth of an atmosphere (improving from the original Virgo level by a factor of 100). The residual gas molecules, primarily hydrogen and water, have a limited impact on the laser beams' path.[27] Large gate valves are at both ends of the arms so work can be done in the mirror-vacuum towers without breaking an arm's ultra-high vacuum. The towers containing the mirrors and attenuators are split into two sections, with different pressures.[49] The tubes undergo a process, known as baking, in which they are heated to 150 °C (302 °F) to remove unwanted particles from their surfaces; although the towers were also baked in the initial Virgo design, cryogenic traps are now used to prevent contamination.[27]

Due to the interferometer's high power, its mirrors are susceptible to the effects of heating induced by the laser (despite extremely low absorption). These effects can cause deformation of the surface due to dilation or a change in refractive index of the substrate, resulting in power escaping from the interferometer and perturbations of the signal. These effects are accounted for by a thermal compensation system (TCS) which includes Hartmann wavefront sensors (HWS)[50] to measure optical aberration through an auxiliary light source, and two actuators: CO2 lasers (which heat parts of the mirror to correct the defects) and ring heaters, which adjust the mirror's radius of curvature. The system also corrects "cold defects": permanent defects introduced during mirror manufacture.[51][27] During the O3 run, the TCS increased power inside the interferometer by 15 percent and decreased power leaving the interferometer by a factor of two.[52]

A shiny round device, with a hand for scale
A Newtonian calibrator ("NCal") before installation at the detector. Several are installed near an end mirror; movement of the rotor generates a varying gravitational force on the mirror, permitting controlled movement.[53]

Another important component is the system for controlling stray light (any light leaving the interferometer's designated path) by scattering on a surface or from unwanted reflection. Recombination of stray light with the interferometer's main beam can be a significant noise source, often difficult to track and model. Most efforts to mitigate stray light are based on absorbing plates (known as baffles) placed near the optics and within the tubes; additional precautions are needed to prevent the baffles from affecting interferometer operation.[54][55][48]

Calibration is required to estimate the detector's response to gravitational waves and correctly reconstruct the signal. It involves moving the mirrors in a controlled way and measuring the result. During the initial Virgo era, this was primarily achieved by agitating a pendulum on which the mirror is suspended with coils to generate a magnetic field interacting with magnets fixed to the pendulum.[56] This technique was used until O2. For O3, the primary calibration method was photon calibration (PCal); it had been a secondary method to validate the results, using an auxiliary laser to displace the mirror with radiation pressure.[57][58] A method known as Newtonian calibration (NCal) was introduced at the end of O2 to validate the Pcal results; it relies on gravity to move the mirror, placing a rotating mass at a specific distance from it.[59][58] At the beginning of the second part of O4, Ncal became the main calibration method because it performed better than Pcal; Pcal is still used to validate Ncal results and probe higher frequencies which are inaccessible to the Ncal.[53]

The instrument requires an efficient data-acquisition system which manages data measured at the interferometer's output and from sensors on the site, writing it in files and distributing the files for data analysis. Dedicated hardware and software have been developed for Virgo.[60]

Noise and sensitivity

[edit]

Noise sources

[edit]
Graph and corresponding visualization of an anomaly
"Koi fish" glitch from 2015 LIGO Hanford data. The top is the detector output (strain) as a function of time, and the bottom is the frequency distribution of the power. This type of glitch is of unknown origin and covers a broad frequency range, with characteristic "fins" at lower frequencies.[61]

The Virgo detector is sensitive to several noise sources which limit its ability to detect gravitational-wave signals. Some have large frequency ranges and limit the overall sensitivity of the detector,[62][48] such as:

  • seismic noise (any ground motion from sources such as waves in the Mediterranean Sea, wind, or human activity), generally in low frequencies up to about 10 Hertz (Hz)
  • thermal noise of the mirrors and their suspension wires corresponding to the agitation of the mirror or suspension from its own temperature, from a few tens to a few hundred Hz
  • quantum noise, which includes laser shot noise corresponding to fluctuation in power received by the photodiodes and relevant above a few hundred Hz, and radiation pressure noise corresponding to pressure by the laser on the mirror (relevant at low frequency)
  • Newtonian noise, caused by tiny fluctuations in the Earth's gravitational field which affect the position of the mirror; relevant below 20 Hz

In addition to these broad noise sources, others may affect specific frequencies. These include a source at 50 Hz (and harmonics at 100, 150, and 200 Hz), corresponding to the frequency of the European power grid; "violin modes" at 300 Hz (and several harmonics), corresponding to the resonant frequency of the suspension fibers (which can vibrate at a specific frequency, as the strings of a violin do); and calibration lines, appearing when mirrors are moved for calibration.[63][64]

Additional noise sources may have a short-term impact; bad weather or earthquakes may temporarily increase the noise level.[48] Short-lived artifacts may appear in the data due to many possible instrumental issues, and are usually referred to as "glitches". It is estimated that about 20 percent of detected events are impacted by glitches, requiring specific data-processing methods to mitigate their impact.[65]

Detector sensitivity

[edit]
A graph
Sensitivity curve in the Virgo detector from 10 Hz to 10 kHz, computed in August 2011.[66][67] Its shape is typical; the thermal noise of the mirror suspension pendulum dominates at low frequency, and the increase at high frequency is due to laser shot noise. In between are resonances and instrumental noises, including the 50-Hz utility frequency and its harmonics.[62]

Sensitivity depends on frequency, and is usually represented as a curve corresponding to the noise power spectrum (or amplitude spectrum, the square root of the power spectrum); the lower the curve, the greater the sensitivity. Virgo is a wide-band detector whose sensitivity ranges from a few Hz to 10 kHz; a 2011 Virgo sensitivity curve is plotted with a log-log scale.[68]

The most common measure of gravitational-wave-detector sensitivity is the horizon distance, defined as the distance at which a binary neutron star with masses 1.4 M☉–1.4 M☉ (where M☉ is the solar mass) produces a signal-to-noise ratio of 8 in the detector. It is generally expressed in megaparsecs.[69] The range for Virgo during the O3 run was between 40 and 50 Mpc.[6] This range is an indicator, not a maximal range for the detector; signals from more massive sources will have a larger amplitude, and can be detected from further away.[70]

Calculations indicate that the detector sensitivity roughly scales as , where is the arm-cavity length and the laser power on the beam splitter. To improve it, these quantities must be increased. This is achieved with long arms, optical cavities inside the arm to maximize exposure to the signal, and power recycling to increase power in the arms.[62][71]

History

[edit]

The Virgo project was approved in 1992 by the French CNRS and the following year by the Italian INFN. Construction of the detector began in 1996 in Santo Stefano a Macerata in Cascina,[72] near Pisa, Italy, and was completed in 2003. After several observation runs in which no gravitational waves were detected, the interferometer was shut down in 2011 for upgrading as part of the Advanced Virgo project. It began making observations again in 2017, quickly making its first detections with the LIGO detectors.[73]

Conception

[edit]

Although the concept of gravitational waves was presented by Albert Einstein in 1916,[74] serious projects for detecting them only began during the 1970s. The first were the Weber bars, invented by Joseph Weber;[75] although they could detect gravitational waves in theory, none of the experiments succeeded. However, they sparked the creation of research groups dedicated to gravitational waves.[33]

The idea of a large interferometric detector began to gain credibility during the early 1980s, and the Virgo project was conceptualized by Italian researcher Adalberto Giazotto and French researcher Alain Brillet in 1985 after they met in Rome. A key idea that set Virgo apart from other projects was the targeting of low frequencies (around 10 Hz); most projects focused on higher frequencies (around 500 Hz). Many believed at the time that low-frequency observations were not possible; only France and Italy began work on the project,[76] which was first proposed in 1987.[77] After approval by the CNRS and the INFN, construction of the interferometer began in 1996 with the aim of beginning observations by 2000.[78]

Virgo's first goal was to directly observe gravitational waves, whose existence was already indirectly evidenced by the three-decade study of the binary pulsar 1913+16: the observed decrease of this binary pulsar's orbital period was in agreement with the hypothesis that the system was losing energy by emitting gravitational waves.[79]

Initial Virgo detector

[edit]

The Virgo detector was first built, commissioned and operated during the 2000s, and reached its expected sensitivity. This validated its design choices, and demonstrated that giant interferometers were promising devices for detecting gravitational waves in a broad frequency band.[80][81] This phase is sometimes called the "initial Virgo" or "original Virgo".[82][83]

Construction of the initial Virgo detector was completed in June 2003,[26] and several data collection periods ("science runs") followed between 2007 and 2011, after 4 years of commissioning.[84][34] Some of the runs were performed with the two LIGO detectors (which are located in Hanford, Washington and in Livingston, Louisiana[85]). There was a shut-down of a few months in 2010 for an upgrade of the Virgo suspension system, and the original steel suspension wires were replaced by glass fibers to reduce thermal noise.[86] Even after several months of data collection with the upgraded suspension system, no gravitational waves were observed, and the detector was shut down in September 2011 for the installation of Advanced Virgo.[87]

Advanced Virgo detector

[edit]
Six graphs and three graphics
First direct detection of a gravitational wave by Virgo on 14 August 2017 (GW170814)

The Advanced Virgo detector aimed to increase the sensitivity (and the distance from which a signal can be detected) by a factor of 10, allowing it to probe a volume of the universe 1,000 times larger and making detection of gravitational waves more likely.[76][40] It benefited from the experience gained with the initial detector and technological advances.[40]

The Advanced Virgo detector kept the same vacuum infrastructure as the initial Virgo, but the rest of the interferometer was upgraded. Four additional cryotraps were added at both ends of each arm to trap residual particles coming from the mirror towers. The new mirrors were larger, with a diameter of 35 cm (14 in) and a weight of 40 kg (88 lb), and their optical performance was improved. The optical elements used to control the interferometer were under vacuum on suspended mountings. A system of adaptive optics were installed to correct the mirror aberrations in situ. In the original plan, the laser power was expected to reach 200 W in its final configuration.[27]

Advanced Virgo began the commissioning process in 2016, joining the two LIGO detectors (which had gone through similar upgrades with Advanced LIGO) on 1 August 2017. Observation "runs" for the Advanced detector era are planned by the LVK collaboration with the goal to maximize the observing time with several detectors, and are labelled O1 to O5; Virgo began participating to these near the end of the O2 run. LIGO and Virgo detected the GW170814 signal on 14 August 2017, which was reported on 27 September of that year. It was the first binary black hole merger detected by both LIGO and Virgo, and the first for Virgo.[88][89]

GW170817 was detected by LIGO and Virgo on 17 August 2017. The signal, produced by the final minutes of two neutron stars spiralling closer to each other and merging, was the first binary neutron-star merger observed and the first gravitational-wave observation confirmed by non-gravitational means. The resulting gamma-ray burst was also detected, and optical telescopes later discovered a kilonova corresponding to the merger.[5][90]


After further upgrades, Virgo began its third observation run (O3) in April 2019. Planned to last one year,[91] the run ended early on 27 March 2020 due to the COVID-19 pandemic.[92]

The upgrades following O3 are part of the Advanced Virgo + program, divided into two phases; the first preceded the O4 run, and the second precedes the O5 run. The first phase focused on the reduction of quantum noise by introducing a more powerful laser, improving the squeezing introduced in O3, and implementing a new technique known as signal recycling; seismic sensors were also installed around the mirrors. The second phase will attempt to reduce the mirror thermal noise by changing the geometry of the laser beam to increase its size on the mirrors (spreading the energy on a larger area and thus reducing the temperature) and improving the coating of the mirrors; the end mirrors will be larger, requiring improvements to the suspension. Further improvements for quantum noise reduction are also expected in the second phase, building on the changes in the first.[23]

The fourth observation run (O4) was scheduled to begin in May 2023 and was planned to last for 20 months, including a commissioning break of up to two months.[6] On 11 May 2023, Virgo announced that it would not join the beginning of O4; the interferometer was not stable enough to reach the expected sensitivity and one mirror needed replacement, requiring several weeks of work.[93] Virgo did not join the O4 run during its first part (O4a, which ended on 16 January 2024), since it only reached a peak sensitivity of 45 Mpc instead of the 80 to 115 Mpc initially expected; it joined the second part of the run (O4b), which began on 10 April 2024, with a sensitivity of 50 to 55 Mpc. In June 2024, it was announced that the O4 run would last until 9 June 2025 to further prepare for the O5 upgrades.[6]

Future

[edit]

The detector will again be shut down for upgrades, including mirror-coating improvement, after the O4 run. A fifth observing run (O5) is planned to begin around June 2027. Virgo's target sensitivity, originally set at 150–260 Mpc, is being redefined in light of its performance during O4. Plans to enter the O5 run are expected to be known before the end of 2024.[6]

No official plans have been announced for the future of the Virgo installations after the O5 period, although projects for improving the detectors have been suggested. The collaboration's current plans are known as the Virgo_nEXT project.[94]

Data analysis

[edit]
Main article: Ground-based interferometric gravitational-wave search § Data analysis

An important part of Virgo collaboration resources is dedicated to the development and deployment of data-analysis software designed to process the detector's output. Apart from the data-acquisition software and tools for distributing the data, the effort is shared with members of the LIGO and KAGRA collaborations as part of the LIGO-Virgo-KAGRA (LVK) collaboration.[12]

Data from the detector is initially only available to LVK members. Segments of data surrounding detected events are released at the publication of the related paper, and the full data is released after a proprietary period (currently 18 months). During the third observing run (O3), this resulted in two separate data releases (O3a and O3b) corresponding to the first and last six months of the run.[95] The data is then generally available on the Gravitational Wave Open Science Center (GWOSC) platform.[96][97]

Analysis of the data requires a variety of techniques targeting different types of sources. Most of the effort is dedicated to the detection and analysis of mergers of compact objects, the only type of source detected until now. Analysis software is running the data in search of this type of event, and a dedicated infrastructure is used to alert the online community.[98] Other efforts are carried out after the data-acquisition period (offline), including searches for continuous sources,[99] a stochastic background,[100] or deeper analysis of detected events.[98]

Scientific results

[edit]
Map of the entire sky using the Mollweide projection, showing two areas corresponding to the localization of an event using only the 2 LIGO detectors, and using both LIGO and Virgo. The area with the 3 detectors is smaller by a factor 20.
Sky localization of the GW170814 event with the two LIGO detectors and the full network. The addition of Virgo allows for more-precise localization.
Further information: List of gravitational wave observations

Virgo first detected a gravitational signal during the second observation run (O2) of the "advanced" era; only the LIGO detectors were operating during the first observation run. The event, named GW170814, was a coalescence between two black holes. It was the first event detected by three different detectors, allowing for greatly-improved localization compared to events from the first observation run. It also allowed for the first conclusive measure of gravitational-wave polarization, providing evidence against polarizations other than those predicted by general relativity.[88]

It was soon followed by the better-known GW170817, the first merger of two neutron stars detected by the gravitational-wave network and (by October 2024) the only event with a confirmed detection of an electromagnetic counterpart in gamma rays, optical telescopes, radio and x-ray domains. No signal was observed in Virgo, but this absence was crucial to more tightly constrain the event's localization, as it allows to exclude regions of the sky where the signal would have been visible in Virgo data.[5] This event, involving over 4,000 astronomers,[101] improved the understanding of neutron-star mergers[102] and putting tight constraints on the speed of gravity.[103]

Several searches for continuous gravitational waves have been performed on data from past runs. O3-run searches include an all-sky search,[104] targeted searches toward Scorpius X-1[105] and several known pulsars (including the Crab and Vela pulsars),[106][107] and a directed search towards the supernova remnants Cassiopeia A and Vela Jr.[108] and the Galactic Center.[109] Although none of the searches identified a signal, this enabled upper limits to be set on some parameters; in particular, it was found that the deviation from perfect spinning balls for close known pulsars is (at most) 1 mm (0.039 in).[104]

Virgo was included in the latest search for a gravitational-wave background with LIGO, combining the results of O3 with the O1 and O2 runs (which only used LIGO data). No stochastic background was observed, improving previous constraints on the energy of the background by an order of magnitude.[110]

Broad estimates of the Hubble constant have also been obtained; the current best estimate is 68+12
-8 km s−1 Mpc−1, combining results from binary black holes and the GW170817 event. This result is consistent with other estimates of the constant, but not precise enough to solve the current debates about its exact value.[20]

Outreach

[edit]

The Virgo collaboration participates in several activities promoting communication and education about gravitational waves for the general public.[111] One important activity is the organization of guided tours of the Virgo facilities for schools, universities, and the public;[112] however, many of outreach activities take place outside the Virgo site. This includes public lectures and courses about Virgo activities[111] and participation in science festivals,[113][114][115] which develops methods and devices for the public understanding of gravitational waves and related topics. The collaboration is involved in several artistic projects, ranging from visual projects such as "The Rhythm of Space" at the Museo della Grafica in Pisa[116] and "On Air" at the Palais de Tokyo[117] to concerts.[118] It includes activities promoting gender equality in science, highlighting women working in Virgo in communications to the general public.[119]

[edit]
  • Panorama of the site, with mountains in the background
    Overview of the Virgo site
  • See caption
    Aerial view of the detector
  • The north arm, with mountains in the background
    The 3-km-long (1.9 mi) north arm
  • Above-ground view of the site, with parked cars for scale
    (Front) Detector control-room building and local computer center
  • A square, white, windowless building with three flags in front
    The central building, which hosts the laser and the beamsplitter mirror
  • Two blue tubes, one much longer than the other
    The mode-cleaner cavity (left, which filters the laser beam) and the west arm

References

[edit]
  1. ^ a b "Our mission". www.ego-gw.it. European Gravitational Observatory. Retrieved 11 October 2023.
  2. ^ "The Virgo Collaboration". virgo-gw.eu. The Virgo Collaboration. 18 February 2021. Retrieved 11 October 2023.
  3. ^ a b "LIGO-M060038-v5: Memorandum of Understanding (MoU) Between VIRGO and LIGO". dcc.ligo.org. Retrieved 4 July 2023.
  4. ^ "Virgo Interferometer for the Detection of Gravitational Waves". eoPortal. 1 April 2019. Retrieved 26 July 2024.
  5. ^ a b c Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K. (16 October 2017). "Multi-messenger Observations of a Binary Neutron Star Merger". The Astrophysical Journal. 848 (2): L12. arXiv:1710.05833. Bibcode:2017ApJ...848L..12A. doi:10.3847/2041-8213/aa91c9. ISSN 2041-8213. S2CID 217162243.
  6. ^ a b c d e "IGWN | Observing Plans". observing.docs.ligo.org. Retrieved 16 January 2024.
  7. ^ "Communique de presse – Le CNRS signe l'accord franco-italien de création du consortium EGO European Gravitational Observatory" [Press release - The CNRS signs the franco-italian agreement on the creation of the EGO (European Gravitational Observatory) consortium.]. Cnrs.fr (in French). Archived from the original on 5 March 2016. Retrieved 11 February 2016.
  8. ^ Carpinelli, Massimo (12 July 2023). "EGO Council report" (PDF). Retrieved 15 November 2024.
  9. ^ "LIGO and Virgo detectors restart gravitational wave observation". Virgo. Retrieved 28 October 2024.
  10. ^ a b "The Virgo Institutions". virgo-gw.eu. The Virgo Collaboration. Retrieved 28 October 2024.
  11. ^ "Scientific Collaboration – Virgo". www.virgo-gw.eu. Retrieved 31 March 2023.
  12. ^ a b "Our Collaborations". LIGO Lab | Caltech. Retrieved 26 February 2023.
  13. ^ "LIGO Scientific Collaboration - Learn about the LSC". www.ligo.org. Retrieved 31 March 2023.
  14. ^ "KAGRA to Join LIGO and Virgo in Hunt for Gravitational Waves". LIGO Lab | Caltech. Retrieved 4 July 2023.
  15. ^ "Sources and Types of Gravitational Waves". LIGO website. Retrieved 21 October 2024.
  16. ^ "Astrophysical Sources of Gravitational Waves". Virgo. Retrieved 17 May 2024.
  17. ^ Eardley, Douglas M.; Lee, David L.; Lightman, Alan P.; Wagoner, Robert V.; Will, Clifford M. (30 April 1973). "Gravitational-Wave Observations as a Tool for Testing Relativistic Gravity". Physical Review Letters. 30 (18): 884–886. Bibcode:1973PhRvL..30..884E. doi:10.1103/PhysRevLett.30.884. hdl:2060/19730012613. S2CID 120335306.
  18. ^ Abbott, R.; et al. (2021). "Search for Lensing Signatures in the Gravitational-Wave Observations from the First Half of LIGO–Virgo's Third Observing Run". The Astrophysical Journal. 923 (1): 14. arXiv:2105.06384. Bibcode:2021ApJ...923...14A. doi:10.3847/1538-4357/ac23db. S2CID 234482851.
  19. ^ Van Den Broeck, Chris (2014). "Probing Dynamical Spacetimes with Gravitational Waves". In Ashtekar, Abhay; Petkov, Vesselin (eds.). Springer Handbook of Spacetime. Springer Handbooks. Berlin, Heidelberg: Springer. pp. 589–613. arXiv:1301.7291. Bibcode:2014shst.book..589V. doi:10.1007/978-3-642-41992-8_27. ISBN 978-3-642-41992-8. S2CID 119242493. Retrieved 23 April 2023.
  20. ^ a b The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K. (2023). "Constraints on the Cosmic Expansion History from GWTC–3". The Astrophysical Journal. 949 (2): 76. arXiv:2111.03604. Bibcode:2023ApJ...949...76A. doi:10.3847/1538-4357/ac74bb. S2CID 243832919.
  21. ^ "What is an Interferometer?". LIGO website. Retrieved 21 October 2024.
  22. ^ Vinet, Jean-Yves; The Virgo Collaboration (2006). The VIRGO physics book Vol. II (PDF). p. 19.
  23. ^ a b c d e Flaminio, Raffaele (13 December 2020). "Status and plans of the Virgo gravitational wave detector". In Marshall, Heather K.; Spyromilio, Jason; Usuda, Tomonori (eds.). Ground-based and Airborne Telescopes VIII (PDF). SPIE Conference Series. Vol. 11445. SPIE. pp. 205–214. Bibcode:2020SPIE11445E..11F. doi:10.1117/12.2565418. ISBN 9781510636774. S2CID 230549331.
  24. ^ F. Bondu; et al. (1996). "Ultrahigh-spectral-purity laser for the VIRGO experiment". Optics Letters. 21 (8): 582–4. Bibcode:1996OptL...21..582B. doi:10.1364/OL.21.000582. PMID 19876090.
  25. ^ F. Bondu; et al. (2002). "The VIRGO injection system" (PDF). Classical and Quantum Gravity. 19 (7): 1829–1833. Bibcode:2002CQGra..19.1829B. doi:10.1088/0264-9381/19/7/381. S2CID 250902832.
  26. ^ a b Acernese, F.; Amico, P.; Al-Shourbagy, M.; Aoudia, S.; Avino, S.; et al. (August 2004). "The status of VIRGO". 5th Rencontres du Vietnam Particle Physics and Astrophysics. Hanoi, Vietnam: 1–6 – via HAL.
  27. ^ a b c d e f g h i Many authors of the Virgo Collaboration (13 April 2012). Advanced Virgo Technical Design Report VIR–0128A–12 (PDF).
  28. ^ Wei, Li-Wei (3 December 2015). High-power laser system for Advanced Virgo gravitational wave detector : coherently combined master oscillator fiber power amplifiers (PhD thesis). Université Nice Sophia Antipolis.
  29. ^ "Optical Layout – Virgo". www.virgo-gw.eu. Retrieved 5 March 2023.
  30. ^ J. Degallaix (2015). "Silicon, the test mass substrate of tomorrow?" (PDF). The Next Detectors for Gravitational Wave Astronomy. Archived from the original (PDF) on 8 December 2015. Retrieved 16 December 2015.
  31. ^ R. Bonnand (2012). The Advanced Virgo Gravitational Wave Detector/ Study of the optical design and development of the mirrors (PhD) (in French). Université Claude Bernard – Lyon I.
  32. ^ R Flaminio; et al. (2010). "A study of coating mechanical and optical losses in view of reducing mirror thermal noise in gravitational wave detectors" (PDF). Classical and Quantum Gravity. 27 (8): 084030. Bibcode:2010CQGra..27h4030F. doi:10.1088/0264-9381/27/8/084030. S2CID 122750664.
  33. ^ a b Bersanetti, Diego; Patricelli, Barbara; Piccinni, Ornella Juliana; Piergiovanni, Francesco; Salemi, Francesco; Sequino, Valeria (August 2021). "Advanced Virgo: Status of the Detector, Latest Results and Future Prospects". Universe. 7 (9): 322. Bibcode:2021Univ....7..322B. doi:10.3390/universe7090322. hdl:11568/1161730. ISSN 2218-1997.
  34. ^ a b Accadia, T.; Acernese, F.; Alshourbagy, M.; Amico, P.; Antonucci, F.; Aoudia, S.; Arnaud, N.; Arnault, C.; Arun, K. G.; Astone, P.; Avino, S.; Babusci, D.; Ballardin, G.; Barone, F.; Barrand, G.; Barsotti, L.; Barsuglia, M.; Basti, A.; Bauer, Th S.; Beauville, F.; Bebronne, M.; Bejger, M.; Beker, M. G.; Bellachia, F.; Belletoile, A.; Beney, J. L.; Bernardini, M.; Bigotta, S.; Bilhaut, R.; et al. (29 March 2012). "Virgo: a laser interferometer to detect gravitational waves". Journal of Instrumentation. 7 (3): 03012. Bibcode:2012JInst...7.3012A. doi:10.1088/1748-0221/7/03/P03012.
  35. ^ Boschi, Valerio (1 March 2019). "Seismic isolation in advanced Virgo gravitational wave detector". Journal of the Acoustical Society of America. 145 (3_Supplement): 1668. Bibcode:2019ASAJ..145.1668B. doi:10.1121/1.5101119. ISSN 0001-4966. S2CID 150337668.
  36. ^ M. Lorenzini & Virgo Collaboration (2010). "The monolithic suspension for the virgo interferometer". Classical and Quantum Gravity. 27 (8): 084021. Bibcode:2010CQGra..27h4021L. doi:10.1088/0264-9381/27/8/084021. S2CID 123269358.
  37. ^ Braccini, S.; Barsotti, L.; Bradaschia, C.; Cella, G.; Virgilio, A. Di; Ferrante, I.; Fidecaro, F.; Fiori, I.; Frasconi, F.; Gennai, A.; Giazotto, A.; Paoletti, F.; Passaquieti, R.; Passuello, D.; Poggiani, R. (1 July 2005). "Measurement of the seismic attenuation performance of the VIRGO Superattenuator". Astroparticle Physics. 23 (6): 557–565. Bibcode:2005APh....23..557B. doi:10.1016/j.astropartphys.2005.04.002. ISSN 0927-6505.
  38. ^ a b Beker, M. G.; Blom, M.; van den Brand, J. F. J.; Bulten, H. J.; Hennes, E.; Rabeling, D. S. (1 January 2012). "Seismic Attenuation Technology for the Advanced Virgo Gravitational Wave Detector". Physics Procedia. Proceedings of the 2nd International Conference on Technology and Instrumentation in Particle Physics (TIPP 2011). 37: 1389–1397. Bibcode:2012PhPro..37.1389B. doi:10.1016/j.phpro.2012.03.741. ISSN 1875-3892.
  39. ^ Beauville, F; Buskulic, D; Derome, L; Dominjon, A; Flaminio, R; Hermel, R; Marion, F; Masserot, A; Massonnet, L; Mours, B; Moreau, F; Mugnier, P; Ramonet, J; Tournefier, E; Verkindt, D (7 May 2006). "Improvement in the shot noise of a laser interferometer gravitational wave detector by means of an output mode-cleaner". Classical and Quantum Gravity. 23 (9): 3235–3250. Bibcode:2006CQGra..23.3235B. doi:10.1088/0264-9381/23/9/030. ISSN 0264-9381. S2CID 123072147.
  40. ^ a b c Acernese, F.; Agathos, M.; Agatsuma, K.; Aisa, D.; Allemandou, N.; Allocca, A.; Amarni, J.; Astone, P.; Balestri, G.; Ballardin, G.; Barone, F.; Baronick, J-P; Barsuglia, M.; Basti, A.; Basti, F.; Bauer, Th S.; Bavigadda, V.; Bejger, M.; Beker, M. G.; Belczynski, C.; Bersanetti, D.; Bertolini, A.; Bitossi, M.; Bizouard, M. A.; Bloemen, S.; Blom, M.; Boer, M.; Bogaert, G.; Bondi, D.; et al. (2015). "Advanced Virgo: A second-generation interferometric gravitational wave detector". Classical and Quantum Gravity. 32 (2): 024001. arXiv:1408.3978. Bibcode:2015CQGra..32b4001A. doi:10.1088/0264-9381/32/2/024001. S2CID 20640558.
  41. ^ "Instruments_Laser&optics". the Virgo Collaboration. Retrieved 21 October 2024.
  42. ^ Caves, Carlton M. (15 April 1981). "Quantum-mechanical noise in an interferometer". Physical Review D. 23 (8): 1693–1708. Bibcode:1981PhRvD..23.1693C. doi:10.1103/PhysRevD.23.1693.
  43. ^ The Virgo Collaboration; Acernese, F.; Agathos, M.; Aiello, L.; Ain, A.; Allocca, A.; Amato, A.; Ansoldi, S.; Antier, S.; Arène, M.; Arnaud, N.; Ascenzi, S.; Astone, P.; Aubin, F.; Babak, S. (22 September 2020). "Quantum Backaction on kg-Scale Mirrors: Observation of Radiation Pressure Noise in the Advanced Virgo Detector". Physical Review Letters. 125 (13): 131101. Bibcode:2020PhRvL.125m1101A. doi:10.1103/PhysRevLett.125.131101. hdl:11390/1193696. PMID 33034506. S2CID 222235425.
  44. ^ Virgo Collaboration; Acernese, F.; Agathos, M.; Aiello, L.; Allocca, A.; Amato, A.; Ansoldi, S.; Antier, S.; Arène, M.; Arnaud, N.; Ascenzi, S.; Astone, P.; Aubin, F.; Babak, S.; Bacon, P. (5 December 2019). "Increasing the Astrophysical Reach of the Advanced Virgo Detector via the Application of Squeezed Vacuum States of Light". Physical Review Letters. 123 (23): 231108. Bibcode:2019PhRvL.123w1108A. doi:10.1103/PhysRevLett.123.231108. hdl:11585/709335. PMID 31868444. S2CID 209446443.
  45. ^ Virgo Collaboration; Acernese, F.; Agathos, M.; Ain, A.; Albanesi, S.; Alléné, C.; Allocca, A.; Amato, A.; Amra, C.; Andia, M.; Andrade, T.; Andres, N.; Andrés-Carcasona, M.; Andrić, T.; Ansoldi, S. (25 July 2023). "Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector". Physical Review Letters. 131 (4): 041403. Bibcode:2023PhRvL.131d1403A. doi:10.1103/PhysRevLett.131.041403. hdl:11568/1196710. PMID 37566847. S2CID 260185660.
  46. ^ Zhao, Yuhang; Aritomi, Naoki; Capocasa, Eleonora; Leonardi, Matteo; Eisenmann, Marc; Guo, Yuefan; Polini, Eleonora; Tomura, Akihiro; Arai, Koji; Aso, Yoichi; Huang, Yao-Chin; Lee, Ray-Kuang; Lück, Harald; Miyakawa, Osamu; Prat, Pierre (28 April 2020). "Frequency-Dependent Squeezed Vacuum Source for Broadband Quantum Noise Reduction in Advanced Gravitational-Wave Detectors". Physical Review Letters. 124 (17): 171101. arXiv:2003.10672. Bibcode:2020PhRvL.124q1101Z. doi:10.1103/PhysRevLett.124.171101. PMID 32412296. S2CID 214623227.
  47. ^ Polini, E (1 August 2021). "Broadband quantum noise reduction via frequency dependent squeezing for Advanced Virgo Plus". Physica Scripta. 96 (8): 084003. Bibcode:2021PhyS...96h4003P. doi:10.1088/1402-4896/abfef0. ISSN 0031-8949. S2CID 235285860.
  48. ^ a b c d "Fighting Noises – Virgo". www.virgo-gw.eu. Retrieved 21 February 2023.
  49. ^ VIRGO Vacuum System Overview, A.Pasqualetti https://workarea.ego-gw.it/ego2/virgo/advanced-virgo/vac/varies/Virgo_Vacuum_system_Overview_r2.pdf
  50. ^ Kelly, Thu-Lan; Veitch, Peter J.; Brooks, Aidan F.; Munch, Jesper (20 February 2007). "Accurate and precise optical testing with a differential Hartmann wavefront sensor". Applied Optics. 46 (6): 861–866. Bibcode:2007ApOpt..46..861K. doi:10.1364/AO.46.000861. hdl:2440/43095. ISSN 2155-3165. PMID 17279130.
  51. ^ Rocchi, A; Coccia, E; Fafone, V; Malvezzi, V; Minenkov, Y; Sperandio, L (1 June 2012). "Thermal effects and their compensation in Advanced Virgo". Journal of Physics: Conference Series. 363 (1): 012016. Bibcode:2012JPhCS.363a2016R. doi:10.1088/1742-6596/363/1/012016. ISSN 1742-6596. S2CID 122763506.
  52. ^ Nardecchia, Ilaria (2022). "Detecting Gravitational Waves with Advanced Virgo". Galaxies. 10 (1): 28. Bibcode:2022Galax..10...28N. doi:10.3390/galaxies10010028. ISSN 2075-4434.
  53. ^ a b Aubin, Florian; Dangelser, Eddy; Estevez, Dimitri; Masserot, Alain; Mours, Benoît; Pradier, Thierry; Syx, Antoine; Van Hove, Pierre (6 September 2024). "The Virgo Newtonian calibration system for the O4 observing run". arXiv:2406.10028 [gr-qc].
  54. ^ Vinet, Jean-Yves; Brisson, Violette; Braccini, Stefano; Ferrante, Isidoro; Pinard, Laurent; Bondu, François; Tournié, Eric (15 November 1997). "Scattered light noise in gravitational wave interferometric detectors: A statistical approach". Physical Review D. 56 (10): 6085–6095. Bibcode:1997PhRvD..56.6085V. doi:10.1103/PhysRevD.56.6085.
  55. ^ Vinet, Jean-Yves; Brisson, Violette; Braccini, Stefano (15 July 1996). "Scattered light noise in gravitational wave interferometric detectors: Coherent effects". Physical Review D. 54 (2): 1276–1286. Bibcode:1996PhRvD..54.1276V. doi:10.1103/PhysRevD.54.1276. PMID 10020804.
  56. ^ Accadia, T; Acernese, F; Antonucci, F; Astone, P; Ballardin, G; Barone, F; Barsuglia, M; Basti, A; Bauer, Th S; Beker, M G; Belletoile, A; Birindelli, S; Bitossi, M; Bizouard, M A; Blom, M (21 January 2011). "Calibration and sensitivity of the Virgo detector during its second science run". Classical and Quantum Gravity. 28 (2): 025005. arXiv:1009.5190. Bibcode:2011CQGra..28b5005A. doi:10.1088/0264-9381/28/2/025005. ISSN 0264-9381. S2CID 118586058.
  57. ^ Estevez, D; Lagabbe, P; Masserot, A; Rolland, L; Seglar-Arroyo, M; Verkindt, D (25 February 2021). "The Advanced Virgo photon calibrators". Classical and Quantum Gravity. 38 (7): 075007. arXiv:2009.08103. Bibcode:2021CQGra..38g5007E. doi:10.1088/1361-6382/abe2db. ISSN 0264-9381. S2CID 221761337.
  58. ^ a b Acernese, F; Agathos, M; Ain, A; Albanesi, S; Allocca, A; Amato, A; Andrade, T; Andres, N; Andrić, T; Ansoldi, S; Antier, S; Arène, M; Arnaud, N; Assiduo, M; Astone, P (21 January 2022). "Calibration of advanced Virgo and reconstruction of the detector strain h(t) during the observing run O3". Classical and Quantum Gravity. 39 (4): 045006. arXiv:2107.03294. Bibcode:2022CQGra..39d5006A. doi:10.1088/1361-6382/ac3c8e. hdl:11368/3006794. ISSN 0264-9381. S2CID 238634092.
  59. ^ Estevez, D; Lieunard, B; Marion, F; Mours, B; Rolland, L; Verkindt, D (9 November 2018). "First tests of a Newtonian calibrator on an interferometric gravitational wave detector". Classical and Quantum Gravity. 35 (23): 235009. arXiv:1806.06572. Bibcode:2018CQGra..35w5009E. doi:10.1088/1361-6382/aae95f. ISSN 0264-9381. S2CID 119192600.
  60. ^ Acernese, F.; Amico, P.; Alshourbagy, M.; Antonucci, F.; Aoudia, S.; Astone, P.; Avino, S.; Babusci, D.; Ballardin, G.; Barone, F.; Barsotti, L.; Barsuglia, M.; Bauer, Th. S.; Beauville, F.; Bigotta, S. (April 2007). "Data Acquisition System of the Virgo Gravitational Waves Interferometric Detector". 2007 15th IEEE-NPSS Real-Time Conference. pp. 1–8. doi:10.1109/RTC.2007.4382842. ISBN 978-1-4244-0866-5. S2CID 140107498.
  61. ^ Glanzer, J.; Banagiri, S.; Coughlin, S. B.; Soni, S.; Zevin, M.; Berry, C. P. L.; Patane, O.; Bahaadini, S.; Rohani, N.; Crowston, K.; Kalogera, V.; Østerlund, C.; Katsaggelos, A. (16 March 2023). "Data quality up to the third observing run of Advanced LIGO: Gravity Spy glitch classifications". Classical and Quantum Gravity. 40 (6): 065004. arXiv:2208.12849. Bibcode:2023CQGra..40f5004G. doi:10.1088/1361-6382/acb633. ISSN 0264-9381. S2CID 251903127.
  62. ^ a b c G. Vajente (2008). Analysis of sensitivity and noise sources for the Virgo gravitational wave interferometer (PDF).
  63. ^ "O2 Instrumental Lines". www.gw-openscience.org. Retrieved 24 March 2023.
  64. ^ "Virgo Logbook - Detector Characterisation (Spectral lines)". logbook.virgo-gw.eu. Retrieved 24 March 2023.
  65. ^ Davis, D; Littenberg, T B; Romero-Shaw, I M; Millhouse, M; McIver, J; Di Renzo, F; Ashton, G (15 December 2022). "Subtracting glitches from gravitational-wave detector data during the third LIGO-Virgo observing run". Classical and Quantum Gravity. 39 (24): 245013. arXiv:2207.03429. Bibcode:2022CQGra..39x5013D. doi:10.1088/1361-6382/aca238. ISSN 0264-9381. S2CID 250334515.
  66. ^ "Virgo Sensitivity Curves". 2011. Archived from the original on 1 December 2015. Retrieved 15 December 2015.
  67. ^ Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V.; Affeldt, C.; Agathos, M. (21 January 2015). "Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data". Physical Review D. 91 (2). doi:10.1103/PhysRevD.91.022004. ISSN 1550-7998.
  68. ^ "Sensitivity". Virgo. Retrieved 21 October 2024.
  69. ^ Chen, Hsin-Yu; Holz, Daniel E; Miller, John; Evans, Matthew; Vitale, Salvatore; Creighton, Jolien (4 March 2021). "Distance measures in gravitational-wave astrophysics and cosmology". Classical and Quantum Gravity. 38 (5): 055010. arXiv:1709.08079. Bibcode:2021CQGra..38e5010C. doi:10.1088/1361-6382/abd594. ISSN 0264-9381. S2CID 119057584.
  70. ^ Chen, Hsin-Yu; Holz, Daniel E.; Miller, John; Evans, Matthew; Vitale, Salvatore; Creighton, Jolien (4 March 2021). "Distance measures in gravitational-wave astrophysics and cosmology". Classical and Quantum Gravity. 38 (5): 055010. doi:10.1088/1361-6382/abd594. ISSN 0264-9381.
  71. ^ Hello, Patrice (1997). Détection des ondes gravitationnelles - Ecole Joliot Curie [Detection of gravitational waves - Joliot Curie School] (PDF) (Report) (in French). Retrieved 20 April 2023.
  72. ^ "Cascina, Santo Stefano a Macerata | Virgo Center". Terre di Pisa. Retrieved 17 November 2024.
  73. ^ "Virgo History". Virgo. Retrieved 1 October 2024.
  74. ^ Einstein, Albert (1 January 1916). "Näherungsweise Integration der Feldgleichungen der Gravitation" [Approximative Integration of the Field Equations of Gravitation]. Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften (Minutes of the Royal Prussian Academy of Sciences) (in German): 688–696. Bibcode:1916SPAW.......688E.
  75. ^ Weber, J. (3 June 1968). "Gravitational-Wave-Detector Events". Physical Review Letters. 20 (23): 1307–1308. Bibcode:1968PhRvL..20.1307W. doi:10.1103/PhysRevLett.20.1307.
  76. ^ a b Giazotto, Adalberto (2018). La musica nascosta dell'universo: La mia vita a caccia delle onde gravitazionali [The hidden music of the Universe : my life of running after gravitational waves] (in Italian). Turin: Einaudi. ASIN B07FY52PGV. Bibcode:2018lmnd.book.....G.
  77. ^ Giazotto, Adalberto; Milano, Leopoldo; Bordoni, Franco; Brillet, Alain; Tourrenc, Philippe (12 May 1987). Proposta di Antenna interferometrica a grande base per la ricerca di Onde Gravitazionali [Proposition for an interferometric antenna with long arms for searching gravitational waves] (PDF). ego-gw.it (Technical report) (in Italian).
  78. ^ Caron, B.; Dominjon, A.; Drezen, C.; Flaminio, R.; Grave, X.; Marion, F.; Massonnet, L.; Mehmel, C.; Morand, R.; Mours, B.; Yvert, M.; Babusci, D.; Giordano, G.; Matone, G.; Mackowski, J. -M. (1 May 1996). "Status of the VIRGO experiment". Nuclear Physics B - Proceedings Supplements. Proceedings of the Fourth International Workshop on Theoretical and Phenomenological Aspects of Underground Physics. 48 (1): 107–109. Bibcode:1996NuPhS..48..107C. doi:10.1016/0920-5632(96)00220-4. ISSN 0920-5632.
  79. ^ J.M. Weisberg and J.H. Taylor (2004). "Relativistic Binary Pulsar B1913+16: Thirty Years of Observations and Analysis". ASP Conference Series. 328: 25. arXiv:astro-ph/0407149. Bibcode:2005ASPC..328...25W.
  80. ^ Riles, K. (2013). "Gravitational Waves: Sources, Detectors and Searches". Progress in Particle and Nuclear Physics. 68: 1–54. arXiv:1209.0667. Bibcode:2013PrPNP..68....1R. doi:10.1016/j.ppnp.2012.08.001. S2CID 56407863.
  81. ^ Sathyaprakash and, B.S.; Schutz, Bernard F. (2009). "Physics, Astrophysics and Cosmology with Gravitational Waves". Living Reviews in Relativity. 12 (1): 2. arXiv:0903.0338. Bibcode:2009LRR....12....2S. doi:10.12942/lrr-2009-2. PMC 5255530. PMID 28163611.
  82. ^ Williams, Matt (28 September 2017). "LIGO and Virgo Observatories Detect Black Holes Colliding". Universe Today. Retrieved 21 October 2024.
  83. ^ "Virgo – European Gravitational Observatory | Department of Physics". df.units.it. Retrieved 21 October 2024.
  84. ^ "Ondes gravitationnelles : Virgo entre dans sa phase d'exploitation scientifique – Communiqués et dossiers de presse" [Gravitational waves : Virgo enters in its scientific exploitation phase - Press releases and communications] (PDF). Cnrs.fr (in French). Retrieved 21 February 2024.
  85. ^ "What is LIGO?".
  86. ^ Lorenzini, Matteo (April 2010). "The monolithic suspension for the Virgo interferometer". Classical and Quantum Gravity. 27 (8): 084021. Bibcode:2010CQGra..27h4021L. doi:10.1088/0264-9381/27/8/084021. S2CID 123269358.
  87. ^ The Virgo Collaboration (2011). "Status of the Virgo project" (PDF). Classical and Quantum Gravity. 28 (11): 114002. Bibcode:2011CQGra..28k4002A. doi:10.1088/0264-9381/28/11/114002. S2CID 59369141.
  88. ^ a b Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K. (6 October 2017). "GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence". Physical Review Letters. 119 (14): 141101. arXiv:1709.09660. Bibcode:2017PhRvL.119n1101A. doi:10.1103/PhysRevLett.119.141101. ISSN 0031-9007. PMID 29053306. S2CID 46829350.
  89. ^ Gibney, Elizabeth (27 September 2017). "European detector spots its first gravitational wave". Nature. Retrieved 21 February 2024.
  90. ^ Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M. (28 February 2018). "GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences". Physical Review Letters. 120 (9): 091101. arXiv:1710.05837. Bibcode:2018PhRvL.120i1101A. doi:10.1103/PhysRevLett.120.091101. PMID 29547330. S2CID 3889124.
  91. ^ Bersanetti, Diego (13 July 2019). "Status of the Virgo gravitational-wave detector and the O3 Observing Run - EPS-HEP2019". cern.ch. Retrieved 29 February 2024.
  92. ^ "LIGO Suspends Third Observing Run (O3)". LIGO Lab | Caltech. Retrieved 16 April 2023.
  93. ^ "Virgo postpones entry into O4 observing run – Virgo". www.virgo-gw.eu. Retrieved 13 May 2023.
  94. ^ The Virgo Collaboration (31 May 2022). Virgo nEXT: beyond the AdV+ project - A concept study (PDF). ego-gw.it (Technical report).
  95. ^ "LIGO-M1000066-v27: LIGO Data Management Plan". dcc.ligo.org. Retrieved 26 February 2023.
  96. ^ "GWOSC". www.gw-openscience.org. Retrieved 5 March 2023.
  97. ^ The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhicary, S.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M. (7 February 2023). "Open Data from the Third Observing Run of LIGO, Virgo, KAGRA, and GEO". The Astrophysical Journal Supplement Series. 267 (2): 29. arXiv:2302.03676. Bibcode:2023ApJS..267...29A. doi:10.3847/1538-4365/acdc9f. S2CID 256627681.
  98. ^ a b The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K. (2023). "GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo during the Second Part of the Third Observing Run". Physical Review X. 13 (4): 041039. arXiv:2111.03606. Bibcode:2023PhRvX..13d1039A. doi:10.1103/PhysRevX.13.041039.
  99. ^ Riles, Keith (2023). "Searches for continuous-wave gravitational radiation". Living Reviews in Relativity. 26 (1): 3. arXiv:2206.06447. Bibcode:2023LRR....26....3R. doi:10.1007/s41114-023-00044-3. S2CID 249642127.
  100. ^ Christensen, Nelson (1 January 2019). "Stochastic gravitational wave backgrounds". Reports on Progress in Physics. 82 (1): 016903. arXiv:1811.08797. Bibcode:2019RPPh...82a6903C. doi:10.1088/1361-6633/aae6b5. ISSN 0034-4885. PMID 30462612. S2CID 53712558.
  101. ^ "Astronomers Catch Gravitational Waves from Colliding Neutron Stars". Sky & Telescope. 16 October 2017. Retrieved 20 February 2023.
  102. ^ Watson, Darach; Hansen, Camilla J.; Selsing, Jonatan; Koch, Andreas; Malesani, Daniele B.; Andersen, Anja C.; Fynbo, Johan P. U.; Arcones, Almudena; Bauswein, Andreas; Covino, Stefano; Grado, Aniello; Heintz, Kasper E.; Hunt, Leslie; Kouveliotou, Chryssa; Leloudas, Giorgos (October 2019). "Identification of strontium in the merger of two neutron stars". Nature. 574 (7779): 497–500. arXiv:1910.10510. Bibcode:2019Natur.574..497W. doi:10.1038/s41586-019-1676-3. ISSN 1476-4687. PMID 31645733. S2CID 204837882.
  103. ^ Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K. (16 October 2017). "Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A". The Astrophysical Journal. 848 (2): L13. arXiv:1710.05834. Bibcode:2017ApJ...848L..13A. doi:10.3847/2041-8213/aa920c. ISSN 2041-8213. S2CID 126310483.
  104. ^ a b LIGO Scientific Collaboration, Virgo Collaboration, and KAGRA Collaboration; Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (28 November 2022). "All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO and Advanced Virgo O3 data". Physical Review D. 106 (10): 102008. arXiv:2201.00697. Bibcode:2022PhRvD.106j2008A. doi:10.1103/PhysRevD.106.102008. hdl:1854/LU-01GXN8M856WCY1YG62A5ACCPTN. S2CID 245650351.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  105. ^ Whelan, John T.; Sundaresan, Santosh; Zhang, Yuanhao; Peiris, Prabath (20 May 2015). "Model-based cross-correlation search for gravitational waves from Scorpius X-1". Physical Review D. 91 (10): 102005. arXiv:1504.05890. Bibcode:2015PhRvD..91j2005W. doi:10.1103/PhysRevD.91.102005. S2CID 59360101.
  106. ^ Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L. (25 May 2022). "Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGO-Virgo Observing Runs". The Astrophysical Journal. 935 (1): 1. arXiv:2111.13106. Bibcode:2022ApJ...935....1A. doi:10.3847/1538-4357/ac6acf. ISSN 0004-637X. S2CID 244709285.
  107. ^ "Narrow-band searches for continuous and long-duration transient gravitational waves from known pulsars in the third LIGO-Virgo observing run". www.ligo.org. 21 December 2021. Retrieved 29 March 2023.
  108. ^ LIGO Scientific Collaboration and Virgo Collaboration; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (28 April 2022). "Search of the early O3 LIGO data for continuous gravitational waves from the Cassiopeia A and Vela Jr. supernova remnants". Physical Review D. 105 (8): 082005. arXiv:2111.15116. Bibcode:2022PhRvD.105h2005A. doi:10.1103/PhysRevD.105.082005. S2CID 244729269.
  109. ^ LIGO Scientific Collaboration, Virgo Collaboration, and KAGRA Collaboration; Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (9 August 2022). "Search for continuous gravitational wave emission from the Milky Way center in O3 LIGO-Virgo data". Physical Review D. 106 (4): 042003. arXiv:2204.04523. Bibcode:2022PhRvD.106d2003A. doi:10.1103/PhysRevD.106.042003. S2CID 248085352.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  110. ^ Abbott, R.; Abbott, T. D.; Abraham, S.; Acernese, F.; Ackley, K.; Adams, A.; Adams, C.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (23 July 2021). "Upper limits on the isotropic gravitational-wave background from Advanced LIGO and Advanced Virgo's third observing run". Physical Review D. 104 (2): 022004. arXiv:2101.12130. Bibcode:2021PhRvD.104b2004A. doi:10.1103/PhysRevD.104.022004. ISSN 2470-0010. S2CID 231719405.
  111. ^ a b "Outreach – Virgo". Virgo. Retrieved 8 May 2023.
  112. ^ "Guided Tour". EGO - European Gravitational Observatory. Retrieved 26 February 2023.
  113. ^ "Le Mappe del Cosmo. Storie che hanno cambiato l'universo". Auditorium Parco della Musica (in Italian). Retrieved 6 June 2024.
  114. ^ "The sounds of the Cosmos". Athens Science Festival. Retrieved 6 June 2024.
  115. ^ Rossi, Giada (23 November 2022). "Black Hole: a new interactive installation by EGO and INFN at Città della Scienza in Naples". EGO - European Gravitational Observatory. Retrieved 8 May 2023.
  116. ^ "Home page". Il Ritmo Dello Spazio (The Rhythm of Space). Retrieved 26 February 2023.
  117. ^ "On Air". Studio Tomás Sarceno. 13 October 2018. Retrieved 26 February 2023.
  118. ^ Rossi, Giada (23 December 2023). "'Cosmic' concert at Teatro Verdi in Pisa to celebrate 20 years of Virgo". EGO - European Gravitational Observatory. Retrieved 6 June 2024.
  119. ^ "International Day of Women and Girls in Science 2023 – Virgo". www.virgo-gw.eu. Retrieved 26 February 2023.
[edit]
Retrieved from "https://en.wikipedia.org/w/index.php?title=Virgo_interferometer&oldid=1258066425"