In the Advanced Virgo+ interferometric gravitational-wave detector, the length control of the Fabry-Pérot cavities in the arms and of the detuned filter cavity, used for generating ...frequency-dependent squeezing, uses an auxiliary green beam at half of the operation laser wavelength (1064 nm). While operating the filter cavity with such a bichromatic control scheme for tens of hours, we observed that the mirror reflection phase shift of the fields at the two wavelengths responds differently to temperature changes in the mirrors, causing a change in the relative resonance condition of the two beams. In this paper we show that this thermal detuning effect can be explained by considering the thermomechanical properties of the mirror coating. Our experimental measurements are in good agreement with the theoretical predictions and allow us to drive requirements on the bicolor coating design and mirror temperature stability for long-term stable cavity control.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The aggregation response of fish populations following the addition of artificial structures to seafloor habitats has been well documented in shallow-water reefs and at deeper structures such as oil ...extraction platforms. A long-term time-lapse camera was deployed for 27 four-month deployment periods at 4100
m in the eastern North Pacific to study abyssal megafauna activity and surface–benthos connections. The unique time-series data set provided by this research presented an opportunity to examine how deep-sea benthopelagic fish and epibenthic megafauna populations were affected by an isolated artificial structure and whether animal surveys at this site were biased by aggregation behavior. Counts were taken of benthopelagic grenadiers,
Coryphaenoides spp., observed per week as well as numbers of the epibenthic echinoid
Echinocrepis rostrata. No significant correlation (
r
s=−0.39;
p=0.11) was found between the duration of deployment (in weeks) and the average number of
Coryphaenoides observed at the site. There was also no evidence of associative behavior around the time-lapse camera by
E. rostrata (
r
s=−0.32;
p=0.19). The results of our study suggest that abyssal fish and epibenthic megafauna do not aggregate around artificial structures and that long-term time-lapse camera studies should not be impacted by aggregation response behaviors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this paper, we summarize the present state-of-the-art on the proof-of-principle experiment of frequency-dependent squeezing implemented through EPR entanglement for Virgo gravitational-wave ...detector and we introduce Virgo subsystem proposal for frequency-dependent squeezing, obtained with a compact apparatus and without the costs required by the infrastructure for the filter cavity.
In August 2017, advanced Virgo joined advanced LIGO for the end of the O2 run, leading to the first gravitational waves detections with the three-detector network. This paper describes the advanced ...Virgo calibration and the gravitational wave strain reconstruction during O2. The methods are the same as the ones developed for the initial Virgo detector and have already been described in previous publications; this paper summarizes the differences and emphasis is put on estimating systematic uncertainties. Three versions of the signal have been computed for the Virgo O2 run, an online version and two post-run reprocessed versions with improved detector calibration and reconstruction algorithm. A photon calibrator has been used to establish the sign of and to make an independent partial cross-check of the systematic uncertainties. The uncertainties reached for the latest version are 5.1% in amplitude, in phase and 20 μs in timing.
Advanced Virgo Status Adams, T.; Aiello, L.; Antier, S. ...
Journal of physics. Conference series,
01/2020, Volume:
1342, Issue:
1
Journal Article
Peer reviewed
Open access
The detection of a gravitational wave signal in September 2015 by LIGO interferometers, announced jointly by LIGO collaboration and Virgo collaboration in February 2016, opened a new era in ...Astrophysics and brought to the whole community a new way to look at - or "listen" to - the Universe. In this regard, the next big step was the joint observation with at least three detectors at the same time. This configuration provides a twofold benefit: it increases the signal-to-noise ratio of the events by means of triple coincidence and allows a narrower pinpointing of GW sources, and, in turn, the search for Electromagnetic counterparts to GW signals. Advanced Virgo (AdV) is the second generation of the gravitational-wave detector run by the Virgo collaboration. After a shut-down lasted 5 years for the upgrade, AdV has being commissioned to get back online and join the two advance LIGO (aLIGO) interferometers to realize the aforementioned scenario. We will describe the challenges and the status of the commissioning of AdV, and its current performances and perspectives. A few lines wil be also devoted to describe the latest achievements, occurred after the TAUP 2017 conference.
Ambient temperature is a critical factor determining the stability of gas hydrate deposits on continental margins. To study this process directly under varying conditions, a monitoring array ...comprising a time-lapse camera and in-situ temperature probes was deployed at a hydrocarbon seep known as Bush Hill, where gas hydrates deposits are exposed at the seafloor in a water depth of 570 m. For intervals of 91 days and 30 days, the digital camera recorded several daily images of a prominent gas hydrate mound consisting of structure II gas hydrate. The temperature probes were constructed with one autonomous thermistor at each end of a 50-cm PVC wand and recorded temperatures with precision of better than 0.1 °C at 30-min intervals over 327 days. One probe was implanted with a tight seal into a drill hole about 7 cm deep in the top of the gas hydrate mound. The second was inserted about 50 cm deep into the adjacent sediments. For each probe, the top thermistor recorded the ambient water temperature, while the bottom thermistor synoptically recorded the internal temperature of the hydrate or sediment. The bottom water temperatures ranged from 6.64 to 9.73 °C with a mean of 7.90 °C and standard deviation of 0.437. Photographic results showed no dramatic changes in the size, shape or gas venting from the mound. By comparing the temperatures recorded at the tips of the probes with the synoptic water temperature, we estimate that thermal diffusivity for the gas hydrate deposit was 7.14·10
−8 to 8.33·10
−8 m
2 s
−1 and was 1.77·10
−7 to 3.01·10
−7 m
2 s
−1 for the sediments at the sites where temperatures were recorded. The diffusivity measured in gas hydrate was lower than that measured under laboratory conditions. Stability of gas hydrate in this setting is not likely to be affected by short-term changes in bottom water temperature within the range observed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A deep-sea time-lapse camera and several temperature probes were deployed on the Gulf of Mexico continental shelf at a biological community associated with a gas hydrate outcropping to study ...topographic and hydrologic changes over time. The deployment site, Bush Hill (GC-185), is located at 27 degrees 47.5' N and 91 degrees 15.0' W at depths of ~540 m. The digital camera recorded one still image every 6 h for July-October in 2001, every 2 h for the month of June 2002, and every 6 h for the month of July 2002. Temperature probes were in place at the site for the entire experimental period. The data recovered provide a record of processes that occur at gas hydrate mounds. Sediment resuspension over the mound causes significant variation in luminosity of the time-lapse photographs. A marked diurnal pattern can be seen in the temperature and luminosity records. No major change in shape or size of the gas hydrate outcrop at this site was observed during this study. Stable topography of the gas hydrate mound, combined with high bacterial activity and sediment turnover, appears to focus biological activity in the mound area. Frequency and recurrence of sediment resuspension indicate that short-term change in the depth and distribution of surface sediments is a feature of the benthos at the site. Because the sediment interface is a critical environment for hydrocarbon oxidation and chemosynthesis, short-term variability and heterogeneity may be important characteristics of these settings. PUBLICATION ABSTRACT
Detector characterization and data quality studies -- collectively referred to as {\em DetChar} activities in this article -- are paramount to the scientific exploitation of the joint dataset ...collected by the LIGO-Virgo-KAGRA global network of ground-based gravitational-wave (GW) detectors. They take place during each phase of the operation of the instruments (upgrade, tuning and optimization, data taking), are required at all steps of the dataflow (from data acquisition to the final list of GW events) and operate at various latencies (from near real-time to vet the public alerts to offline analyses). This work requires a wide set of tools which have been developed over the years to fulfill the requirements of the various DetChar studies: data access and bookkeeping; global monitoring of the instruments and of the different steps of the data processing; studies of the global properties of the noise at the detector outputs; identification and follow-up of noise peculiar features (whether they be transient or continuously present in the data); quick processing of the public alerts. The present article reviews all the tools used by the Virgo DetChar group during the third LIGO-Virgo Observation Run (O3, from April 2019 to March 2020), mainly to analyse the Virgo data acquired at EGO. Concurrently, a companion article focuses on the results achieved by the DetChar group during the O3 run using these tools.
The Advanced Virgo detector has contributed with its data to the rapid growth of the number of detected gravitational-wave (GW) signals in the past few years, alongside the two Advanced LIGO ...instruments. First during the last month of the Observation Run 2 (O2) in August 2017 (with, most notably, the compact binary mergers GW170814 and GW170817), and then during the full Observation Run 3 (O3): an 11-months data taking period, between April 2019 and March 2020, that led to the addition of about 80 events to the catalog of transient GW sources maintained by LIGO, Virgo and now KAGRA. These discoveries and the manifold exploitation of the detected waveforms require an accurate characterization of the quality of the data, such as continuous study and monitoring of the detector noise sources. These activities, collectively named {\em detector characterization and data quality} or {\em DetChar}, span the whole workflow of the Virgo data, from the instrument front-end hardware to the final analyses. They are described in details in the following article, with a focus on the results achieved by the Virgo DetChar group during the O3 run. Concurrently, a companion article describes the tools that have been used by the Virgo DetChar group to perform this work.
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