Name (Last, First, Title)Talk/Poster TitleSessionAbstract
Agathos, Michalis, DrConstraining GW dispersion and the mass of the gravitoncosmologyThe recent detections of gravitational waves (GW) from coalescing black hole binaries have opened a wealth of possibilities for testing GR against alternative theories of gravity. A class of alternative theories can be characterized by the modification of the propagation of GWs. By introducing either a “massive graviton” term or a Lorentz invariance violating term in the GW dispersion relation, we have placed observational bounds on GW dispersion and the graviton mass, in the light of the signals detected so far. I will present the method employed and will give an update of current results. I will finally discuss the intriguing potential of cosmological applications that can make use of this kind of information.
Frajuca, Carlos, Dr.Gravitational Waves Propagation through the Stochastic Background of Gravitational WavescosmologyWith the recent claim that gravitational waves were finally detected and with other efforts around the world for GWs detection, its is reasonable to imagine
that the relic gravitational wave background could be detected in some time in the future and with such information gather some hints about the origin of the universe. But, it´s also be considered that gravity has self-interaction, with such assumption it´s reasonable to expect that these gravitatinal wave will interact with the relic or non-relic GW background by scattering, for example. Such interaction should decresase the distance which such propagating waves could be detected The propagation of gravitational waves (GWs) is analysed in an asymptotically de Sitter space by the perturbation expansion around Minkowski space. Using the case of de Sitter inflationary phase scenario, the perturbation propagates through a FRW background. The GW, using the actual value for the Hubble scale (Ho) , has a damping factor with a very small valor for the size of the observational universe. The stochastic relic GW background is given by a dimensionless function of the frequency. In this work we analize this same damping including the gravitational wave background due to astrophysical sources. Such background is 3 orders of magnitude bigger in some frequencies and produces a higher damping factor.
Isi, MaximilianoTesting GR with the Polarizations of Long-lived Gravitational WavescosmologyThe direct detection of gravitational waves provides the opportunity to measure fundamental aspects of gravity that have never been directly probed before, like the polarization of gravitational waves. We show how long-lived signals (resolvable or stochastic) may be used to measure all 6 possible gravitational polarizations with current detectors. This will allow us to obtain new model-independent, dynamical constraints on deviations from general relativity. We demonstrate this framework on multiple potential sources using simulated data from three advanced-era detectors at design sensitivity.
Cahillane, Craig, Mr.Advanced LIGO Calibration Uncertainty for Precision AstrophysicsDetectors 1Calibration of the Advanced LIGO detectors is the characterization of the detectors’ response to gravitational waves. Understanding the detector response to gravitational waves is crucial to accurately and precisely produce gravitational wave strain data. Estimates of binary black hole parameters like total masses, distance, and sky location depend on the accuracy and precision of calibrated data. Tests of general relativity also rely on properly calibrated data, as miscalibrations could be degenerate with deviations from GR. We describe the method of producing calibration uncertainty estimates for both LIGO detectors in the first and second observation runs.
Mukund, NikhilEffective use of machine learning in commissioning and characterizationDetectors 1We have been able to demonstrate the resourcefulness of machine learning (ML) for commissioning and characterization efforts at the gravitational wave observatories through various applications described below.(1) Understanding why the detector was unable to maintain its lock is something that requires analysis thousands of auxiliary subsystem channels. Lockloss-Monitor installed at LIGO Livingston uses density based clustering and identifies the channels that show abnormal behavior prior to lock loss. (2) SEISMON, the earthquake warning system installed at the sites uses regression to predict the ground motion and provides the probability of staying in lock during an earthquake. (3) Accurate system identification and stable control design are necessary to bring the IFO under control. We automate TF fitting to design stable DSP filters via total variation de-noising and multi-parameter optimization. (4) Glitches often show up in strain data leading to false triggers in astrophysical signal search pipelines. We combine unsupervised clustering and supervised learning to develop classifier that work with minimal training data. (5) The advances in semantic learning can be utilized to efficiently retrieve information from unstructured logbook data maintained at the interferometers. HeyLIGO, our NLP-based recommendation system, facilitates this knowledge discovery that leads to better understanding of the instrument.
Urban, Alex, Dr.Calibration Improvements in Advanced LIGO’s Second Observing RunDetectors 1In the new era of gravitational wave astronomy, one of our primary goals is to measure source parameters and draw astrophysical inferences from observed signals. To do this effectively, we require an accurate calibrated estimate of the gravitational wave strain from our detectors. In this talk, I report on frequency-dependent improvements to the uncertainty in Advanced LIGO’s strain data during its second observing run. I will also discuss improvements to our real-time calibration scheme, which include tracking and correcting for time-dependent changes in each detector. Finally, I will summarize the effect that all this has on astrophysics and parameter estimation.
Aguiar, OdylioThe Brazilian Program on Gravitational Wave DetectionDetectors 2The Brazilian program on gravitational wave detection has three main lines of action. The first one is to participate in the various possible areas of contribution for the LIGO Scientific Collaboration (LSC). Presently we are working on aLIGO detection and characterization and LIGO Voyager R&D. The second is to reassemble the gravitational wave antenna Mario Schenberg (formerly at the Institute of Physics of the University of São Paulo (IFUSP) in São Paulo), now at the National Institute for Space Research (INPE) in São José dos Campos, and their improvement, to leave it with sufficient sensibility for detection/observation. The third is to construct a third generation laser interferometer observatory in South America by an international collaboration. Here we detailed this program further.
Miao, Haixing, DrA unified framework for improving quantum-limited detector sensitivityDetectors 2There are different approaches to improving the quantum-limited sensitivity of advanced gravitational-wave detectors, which involve modification to the input/output optics. They come from different perspectives of the quantum noise, e.g., injecting squeezed light to minimise the the input noise or using a different readout scheme to cancel the radiation pressure noise. With recent understanding of the fundamental quantum limit which is a sensitivity limit beyond the standard quantum limit, we can now put all these approaches under a unified framework and combine them in a systematic way to reach the desired level of sensitivity at different frequencies. This talk will give an introduction to this framework.
Zhao, Chunnong, DrParametric instabilities in future gravitational wave detectorsDetectors 2Parametric instability was observed in Advanced LIGO detectors, and fully controlled at the current optical power level using both thermal tuning and electrostatic feedback control schemes. It is predicted that at designed optical power (4 time higher than the current level) more unstable modes will appear and other control schemes will be required to completely suppress the instability.

For the next generation detector, it would be ideal to start dealing with the problem from the design stage by minimising the parametric instability. Here, I report simulation results of the parametric instability in next generation detectors, such as the Voyage and the long baseline 3rd generation detectors. Through searching parameter regimes of arm cavities, and recycling cavities, we show that there exist optimum regimes where the highest parametric instability gain and the number of unstable modes are minimum.
Leavey, Sean, DrGlasgow speed meter prototype update
The ERC speed meter at the University of Glasgow aims to demonstrate a reduction in quantum noise due to back-action in a Sagnac interferometer over an equivalent Michelson configuration. We will discuss the recent progress made in the construction of our metre-scale vacuum experiment.
Oppermann, Patrick, DrCompact solid state amplifier for advanced GWDs and current status of the Hannover laser development
The advanced LIGO high power oscillator is a complex and difficult to maintain laser system. Currently it is the only single frequency laser system delivering 200W of output power with excellent beam parameters. At the LIGO Livingston observatory a failure of the high power oscillator happened. A possible laser amplifier for aLIGO, amplifying up to 70W is presented. In addition, a 100W amplifier for adv Virgo is introduced. Furthermore, the current results on the laser development of Hannover will be presented.
Wu, David, Dr.The AEI 10m Prototype Facility – towards a standard quantum limited interferometer
As the current generation of gravitation wave detectors are approaching the standard quantum limit (SQL), it is becoming increasing important to investigate techniques to overcome this limit. The AEI 10 m Prototype Facility is currently under construction, which will house a Michelson interferometer at the SQL. This facility will allow for rapid testing of new techniques and technology in an environment closely resembling current generation gravitational wave detectors. An update on the progress and recent developments will be presented. Some of the topics discussed will include seismic isolation tables, laser stabilization, crystalline AlGaAs mirror coatings, and the parallel plate electrostatic drive.
Dal Canton, TitoOrbitally-modulated EM counterparts to NS mergersMultiMess 1The classical high-energy EM counterpart to NS mergers is expected to be a
short-GRB prompt emission powered by the accretion of the dispersed NS material on the remnant BH. In the last few years, a couple models also predicted the emission of a burst of gamma radiation before the merger. If such emission
happens close to the NS surface, the observed burst will be modulated by the
relativistic orbital motion of the source. I will present the features of such
modulation, the prospects for its observability and how it can be used in
analyzing data from the Fermi/GBM detectors as a followup to BNS and NSBH
detections from LIGO and Virgo.
Goldstein, Adam, Dr.Searching for EM Counterparts to Gravitational Waves with the Fermi Gamma-ray Burst MonitorMultiMess 1The Fermi Gamma-ray Burst Monitor (GBM) continuously observes the entire sky that is not occulted by the Earth from 8 keV - 40 MeV with 2 microsecond temporal resolution, with data downlinks every few hours. This wealth of near-realtime all-sky data has lead to the development of continuous sub-threshold data searches for gamma-ray events in coincidence with gravitational wave detections. Additionally, GBM has the ability to localize triggered and un-triggered transient events to a few-degree accuracy, rapidly disseminate the alerts and localization sky maps, and there have been several successful follow-up attempts by wide-field optical telescopes, such as the Palomar Transient Factory, to catch the fading optical afterglow of GBM-triggered GRBs. We discuss the current applications and importance of Fermi GBM in leading the counterpart search effort in the gamma-ray regime. Preliminary results from the GBM follow-up of O1 sub-threshold LIGO triggers will be presented, along with improvements made to the GBM sub-threshold searches during O2.
Anand, Shreya, Ms.Timing Based Sky Localization Accuracy for Third Generation Gravitational Wave DetectorsMultiMess 1We present a preliminary investigation of the potential of third generation gravitational wave detectors for electromagnetic follow-up and host galaxy identification. Using simulated and optimized noise-curves for current and next generation detectors, we calculate the statistical arrival time uncertainty of signals from binary neutron star mergers, as well as the maximal horizon distance and corresponding redshifts to the sources. Our preliminary findings, in agreement with the recent literature on third generation detectors, predict that Cosmic Explorer, a proposed detector, will have the capability to detect BNS mergers from as early as the epoch of reionization (z ~ 10). However, our project uniquely concerns how systematic calibration uncertainty affects sky localization. Based on a frequency-independent toy model of calibration errors we developed, our ability to localize signals with next generation detectors may be significantly affected by calibration uncertainty. Soon, we aim to perform a thorough analysis using a more realistic, frequency dependent systematic uncertainty model, combined with statistical uncertainties in all sky localization parameters. We focus on the question: at what redshift will sky localization accuracy be limited by detector calibration? Our research will be useful in determining the science requirements for next generation detectors in order to do astrophysics with gravitational waves.
Breivik, KatelynConstraining orbital evolution with multi-messenger observations of mass-transferring double white dwarfsMultiMess 2The most prolific source of milliHertz gravitational waves is expected to be the Milky Way population of double white dwarfs (DWDs), which will be observable by the space-based gravitational-wave detector LISA. A subset of these systems may be observable while undergoing stable mass transfer, leading to orbital frequency evolution that differs from the traditional gravitational wave orbital evolution. I will present how observations of these systems by both Gaia and LISA can allow the disentanglement of the gravitational and astrophysical contributions to binary frequency evolution.
Camp, Jordan, Dr.Transient Astrophysics ProbeMultiMess 2Transient Astrophysics Probe (TAP), selected by NASA for a funded Concept Study, is a wide-field high-energy transient mission proposed for flight starting in the late 2020s. TAP’s main science goals, called out as Frontier Discovery areas in the 2010 Decadal Survey, are time-domain astrophysics and counterparts of gravitational wave (GW) detections. The mission instruments include unique imaging soft X-ray optics that allow ~500 deg2 FoV in each of four separate modules; a high sensitivity, 1 deg2 FoV soft X-ray telescope based on single crystal silicon optics; a passively cooled, 1 deg2 FoV Infrared telescope with bandpass 0.6-3 micron; and a set of ~8 small NaI gamma-ray detectors. TAP will observe many events per year of X-ray transients related to compact objects, including tidal disruptions of stars, supernova shock breakouts, neutron star bursts and superbursts, and high redshift Gamma-Ray Bursts. Perhaps most exciting is TAP’s capability to observe X-ray and IR counterparts of GWs involving stellar mass black holes detected by LIGO/Virgo, and possibly X-ray counterparts of GWs from supermassive black holes, detected by LISA and Pulsar Timing Arrays.
Pannarale, Francesco, Dr.Search for Gravitational Waves Associated with Gamma-Ray Bursts During the First Advanced LIGO Observing RunMultiMess 2Gamma-ray bursts are the most luminous electromagnetic events in the universe. They fall into two, broad categories: long-duration bursts, which are powered by the core collapse of rapidly rotating massive stars, and short-duration bursts, for which binary neutron star and neutron star-black hole mergers are the leading progenitor candidates. In both scenarios, gravitational waves are expected to accompany the gamma-ray burst, making these transient phenomena promising events for gravitational-wave follow-up. In this talk, I present the results of the targeted searches for gravitational waves in association with gamma-ray bursts obtained during the first Advanced LIGO observing run, which was carried out between September 2015 and January 2016.
Lin, Chun-yu, Dr.Source localization for eccentric binary with ground-base detector networkMultiMess 3With the EPC (enhanced post-circular) waveform model in the frequency domain, we study the resolution of the parameter estimation with a ground-based detector network via the Fisher matrix analysis and a preliminary Markov Chain Monte Carlo method. The improvement of the source localization is observed, which is also compared with the analytically geometrical expressions based on the arrive time of GW.
Mukherjee, Soma, Dr.Detection of Gravitational Waves from Supernovae: CCSN data analysis effort of the LVC burst groupMultiMess 3The talk will present an overview of current data analysis effort of the LVC Burst group to search for gravitational waves from core collapse supernovae (CCSN), including status of search pipelines, recent results and future plans.
Vinciguerra, Serena, MsConstraining BNS merger rates and X-ray counterpart models with existing dataMultiMess 3Coalescences of compact binaries play a fundamental role in astronomy. They are not only considered the most promising sources of gravitational waves for ground-based detectors such as LIGO and Virgo, but also the central engine of short gamma-ray bursts. In the last decade, multi-wavelength observations of SGRBs and their afterglow showed a variety of unexpected features, posing new theoretical challenges. A growing theoretical effort is being devoted to explain these new observations and, at the same time, to predict the possible electromagnetic counterparts to the gravitational-wave signals from compact binary mergers. In order to validate the different theoretical scenarios, we started a project aimed at constraining models by using archived data from past and present missions.

The core of the project consists in developing an algorithm ("saprEMo"), dedicated to predict the number of events detectable in a survey considering different cosmological evolutions of the compact binary rate and emission models. Remarkably, the same tool can also be used to optimize designs and observation strategies for future instruments. Our first case study focused on the X-ray emission from long-lived binary neutron star merger remnants (as proposed by Siegel & Ciolfi 2016) and the data collected by XMM-Newton during its several years of operations. Our first predictions suggest that few events should be present in XMM-Netwon archived data.
Amato, Alex, PhD studentHigh-Reflection Coatings for Gravitational-Wave Detectors: State of The Art and Future Developmentsoptics 1High-reflection coatings are the dominant source of thermal noise in the largest ground-based gravitational-wave (GW) detectors, limiting their detection band in the central and most sensitive region. Lowering such noise would be highly beneficial not only for GW interferometers but also for other experiments using high-precision optical and quantum transducers, such as frequency standards for laser stabilization, quantum computing devices and opto-mechanical resonators.
The intensity of coating thermal noise is determined –as stated by the fluctuation-dissipation theorem– by the so-called mechanical loss angle, which quantifies the energy dissipation in coatings. Knowledge of this parameter is thus of fundamental importance for the characterization of the sensitivity of present detectors and for the design of low-thermal-noise future detectors as well. The coatings of Advanced LIGO, Advanced Virgo and KAGRA have been deposited by the Laboratoire des Matériaux Avancés (LMA) in Lyon, France, where they have been the object of an extensive campaign of optical and mechanical characterization. We will present an exhaustive summary of the outcomes, highlighting their impact on the performances of advanced detectors.
We will then present the preliminary results of the intense research program presently ongoing at the LMA, aiming at the development of low-thermal-noise optical coatings: improvement of standard materials, selection of new materials, structural analysis and modeling.
Glover, LamarStudy of optical scatterers in coating layers of gravitational wave detector test-mass mirrorsoptics 1Similar in appearance to images of star clusters, photographs of the LIGO Gravitational Wave detector mirrors illuminated by the standing beam were analyzed with DAOPHOT, an astronomical software tool designed to identify stars within images and extract information about the structure of light point sources.  DAOPHOT found hundreds of thousands of weaker, point-like scatterers, uniformly distributed across the mirror surface, ignoring the smear of actual dirt on the mirror.  The amplitude distribution of the observed scatterers implies that they extend through the depth of the coating while their sheer number implies a fundamental, thermodynamic origin.  Theoretical material science considerations indicate that these scatterers are a likely source of the mirror dissipation and thermal noise, perhaps pointing the way towards a mitigation strategy, improved sensitivity of Gravitational Wave observatories and increased Gravitational Wave detection radius into the Universe.
Harry, Gregg, ProfessorShear and Bulk Mechanical Loss in Titania Doped Tantalaoptics 1We report on measurements of mechanical loss of titania-doped tantala, the high index coating material used in all second generation interferometric gravitational wave detectors. We analyze modal Q results using a model of two independent loss angles based on shear and bulk stresses. This is experimental validation of this model of loss angles first presented by Hong et al. We find a clear trend in the two loss angles with frequency. It may be possible that by careful design of future coating taking into account the two separate loss angles, Brownian thermal noise could be reduced in future detectors.
Lovelace, Geoffrey, Prof.Numerically modeling Brownian thermal noise in amorphous and crystalline mirror coatingsoptics 2Brownian coating thermal noise is one of the noises limiting the reach of current and future gravitational-wave detectors. Adopting crystalline mirror coatings, rather than the amorphous coatings used in Advanced LIGO, has the potential to reduce thermal noise; understanding and reducing thermal noise requires accurate theoretical models. Analytic theoretical models are especially challenging in the case of crystalline coatings. In this talk, I will present results from a new, open code that numerically computes Brownian coating thermal noise for amorphous and crystalline thin coatings. After comparing thermal noise in an amorphous coating to an approximate analytic solution, demonstrating expected scaling laws, I will present results comparing amorphous and crystalline coating thermal noise. These results are a step toward the long-term goal of better understanding and reducing coating thermal noise in future gravitational-wave detectors.
TORNASI, Zeno, PhD studentOptical properties of silicon for cryogenic interferferometric gravitational wave detectorsoptics 2The next generation of interferometric gravitational wave detectors (GWDs), like Cosmic Explorer or Einstein Telescope, will likely be cryogenic in order to minimise the displacement thermal noise of the arm cavity mirrors. Fused silica core optics, like the ones currently employed at room temperature, would not be suitable in a cryogenic environment: silica exhibits too high a mechanical loss at cryogenic temperatures, that would counteract any gains in thermal noise. Silicon shows an excellent mechanical loss at low temperatures both in its crystalline form (c-Si) and as an amorphous film (a-Si). Silicon optics, with c-Si test masses and a-Si films employed in coatings, offer a promising cryogenic-compatible alternative to silica, albeit at the price of moving the light source from 1064 nm to a wavelength where silicon is transparent, like 1550 nm or 2000 nm. Basic R&D is still needed to understand the optical properties of silicon at the level required for GWDs. We report on the optical absorption of magnetic Czochralski c-Si and ion-beam sputtered a-Si films. We investigate how absorption correlates with deposition parameters and other physical properties of the films. We also report on bulk scattering of magnetic Czochralski c-Si, potentially qualifying this material as suitable substrate for optics that transmit the detector's main beam.
According to its charter, the responsibilities of the LIGO Scientific Collaboration (LSC) include carrying out “an outreach program to communicate LIGO’s activities and goals to the public, and to provide educational opportunities for young people. “ In this talk I will summarize the wide-ranging efforts of the LSC’s Education and Public Outreach (EPO) group, with an emphasis on activities or resources that might be useful for the audience of this talk.
van der Schaaf, Laura, MscPhase cameras for Advanced Virgo: first experienceoptics 2The Phase cameras of the Advanced Virgo detector (AdV) are sensors that monitor both the phases and amplitudes of the carrier and several sidebands simultaneously. At present this information is used in the commissioning of AdV, while in the future the obtained information will be used for the thermal compensation system. The latter system is expected to be crucial for reaching design sensitivity since AdV employs a marginally stable power recycling cavity.
The phase cameras measure amplitudes and phases by scanning the surface of the laser beam over a pinhole diode, applying fast digitization subsequent demodulation with an FPGA. In order to be able to distinguish lower and upper sidebands heterodyne detection is employed. By using an adequate telescope the amplitude and the phase of the field resonating in a specific part of the interferometer can be observed.

By now two phase cameras are in operation and during the commissioning of the interferometer first data has been gathered. In this presentation we will share the first experiences with the phase cameras in AdV.
Jose M. Gonzalez CastroCurrent status of noise hunting in Advanced Virgooptics 2With Virgo on its last step before moving into science mode, we present an overview on the work being done during commissioning of Advanced Virgo to analyze and discover the sources that are producing different lines in the noise spectrum.
Davide GerosaSurprises from the spins: astrophysics and relativity with detections of spinning black-hole mergersPlenaryMeasurements of black-hole spins are of crucial importance to fulfill the promise of gravitational-wave astronomy. On the astrophysics side, spins are perhaps the cleanest indicator of black-hole evolutionary processes, thus providing a preferred way to discriminate how LIGO’s black holes form. On the relativity side, spins are responsible for peculiar dynamical phenomena (from precessional modulations in the long inspiral to gravitational-wave recoils at merger) which encode precious information on the underlying astrophysical processes. I will present some examples to explore this deep and fascinating interplay between spin dynamics (relativity) and environmental effects (astrophysics). Black-hole spins indeed present remarkable surprises on both fronts: instabilities, resonances, constraints on supernova kicks, multiple merger generations and more…
Favata, Marc, Prof.Overview of Education and Public Outreach Activities of the LSCPlenaryEducation and Public Outreach
Gerosa, Davide, DrSurprises from the spinsPlenaryMeasurements of black-hole spins are of crucial importance to fulfill the promise of gravitational-wave astronomy. On the astrophysics side, spins are perhaps the cleanest indicator of black-hole evolutionary processes, thus providing a preferred way to discriminate how LIGO’s black holes form. On the relativity side, spins are responsible for peculiar dynamical phenomena (from precessional modulations in the long inspiral to gravitational-wave recoils at merger) which encode precious information on the underlying astrophysical processes. I will present some examples to explore this deep and fascinating interplay between spin dynamics (relativity) and environmental effects (astrophysics). Black-hole spins indeed present remarkable surprises on both fronts: instabilities, resonances, constraints on supernova kicks, multiple merger generations and more…
Goetz, Evan, Dr.Searches for continuous gravitational waves in the advanced detector eraPlenaryNon-axisymmetric, rapidly rotating neutron stars are predicted to emit continuous quasi-monochromatic gravitational waves. Detecting these waves would provide a unique probe of the astrophysics of neutron stars and General Relativity. The LIGO Scientific Collaboration and Virgo Collaboration have carried out a wide range of different searches for continuous gravitational wave sources: targeted searches for signals from known pulsars using precise electromagnetic ephemerides, directed searches for signals from plausible sources such as Scorpius X-1 but having some unknown source parameters, and all-sky searches for signals from undiscovered neutron stars, including those that are in binary systems. These different searches and, where available, new results using data from the first Observing Run of Advanced LIGO will be presented.
Kawabe, Keita, DrLIGO detectors in O2 and beyondPlenaryAdvanced LIGO instruments are in the second observing run (O2) which is ongoing and is expected to continue until late August, 2017. This talk will review the performance of LIGO instruments in O2, our understanding of the noise sources, and ongoing efforts to further improve the noise performance toward the next observing run O3.
Kawamura, Seiji, Professor; on behalf of the KAGRA collaboration
Current status of KAGRAPlenaryKAGRA is a Large-scale Cryogenic Gravitational Wave Telescope with an arm length of 3 km. It is built underground for the quiet seismic noise and it employs cryogenic Sapphire mirrors to reduce the thermal noise. Initial KAGRA, which was a simple Michelson interferometer with room-temperature fused silica mirrors and simple suspension systems, was already operated successfully. Currently various optical and mechanical components for baseline KAGRA are being installed. In this talk the design of KAGRA, result of the test run of initial KAGRA, current status, schedule, and some preliminary discussions about the future plan of KAGRA will be presented.
McNamara, Paul, drLISA Pathfinder: First Steps to Observing Gravitational Waves from SpacePlenaryLISA Pathfinder, the European Space Agency’s technology demonstration mission for future spaceborne gravitational wave observatories, was launched from Kourou, French Guiana on 3 December 2015. After the transfer to its final science orbit and a short period of instrument commissioning, LISA Pathfinder began science operations on 1 March 2016.

From the first day of operations, it was clear that LISA Pathfinder had met all of its performance requirements, both in terms of the differential acceleration between the test masses, and the performance of the interferometric readout of the test masses’ position.

Over the mission lifetime, the performance has steadily improved, both due to changes in the environment of the instrument (pressure within the electrode housing), and also due to a better understanding of the physics of the instrument by the science team.

LISA Pathfinder has now demonstrated a residual acceleration between two free falling macroscopic bodies to a level better than that required for LISA, over the full LISA measurement bandwidth.

Here, I will give an overview of the mission, focussing on how LISA Pathfinder technology development is paving the way for future detectors, before presenting the on-orbit results and the route to the future.
Metzger, Brian, ProfessorElectromagnetic Counterparts of Compact Binary MergersPlenaryHopes are high that advanced gravitational wave (GW) detectors will detect coalescing binary neutron stars in the next few years. Maximizing the scientific return from this discovery will require identifying a coincident electromagnetic (EM) counterpart. One possible counterpart is a week-long thermal transient, powered by the radioactive decay of neutron-rich elements synthesized in the baryonic ejecta from the merger (a so-called `kilonova', in analogy with normal supernovae). I will present the first 3D MHD simulations of the long-term evolution of the remnant accretion disk produced in NS- NS/NS-BH mergers. Over ~400 ms of evolution, we find the ejection of ~20% of the initial torus mass in powerful neutron-rich winds, confirming this important of this site for the r-process in addition to the dynamical ejecta. I will describe how the lifetime of the hypermassive neutron star, prior to its collapse into a black hole, may impact the kilonova light curves and color. A small fraction of short gamma-ray bursts are accompanied by unexpectedly long-lived X-ray emission, the presence of which suggests that a fraction of mergers could result in the formation of long-lived - or even indefinitely stable - massive neutron star remnants. This outcome, if confirmed by future GW and EM observations, would place stringent constraints on the nuclear density equation of state.
Mitra, Sanjit, Prof.LIGO-India: A Status reportPlenaryDetection of Gravitational Waves (GW) by LIGO marks the birth of GW astronomy. Soon after that the Union cabinet of India announced the in principle approval for a LIGO detector in India. LIGO-India is essential to exploit the immense potential of GW Astronomy. It is a tremendous challenge. With the enormous enthusiasm, LIGO-India's progress has been very good. We believe that the project will be able to meet the aggressive timeline. I will review the status of the LIGO-India project.
Moore, Christopher, DrGravitational Wave Detection With GaiaPlenaryGravitational waves (GWs) cause the apparent position of distant objects to oscillate with a characteristic pattern over the sky. Therefore, astrometric measurements of stellar positions (e.g. those made by the Gaia spacecraft) provide a new way to search for low frequency GWs. I will describe the striking similarity between searches for GWs using astrometric measurements, and searches using pulsar timing measurements. I will then describe how an astrometric search for GWs can be efficiently performed, the sensitivity that can be achieved by Gaia, and some of the key astrophysics questions that can then be addressed.
Vallisneri, Michele, DrThe North-American Nanohertz Observatory for Gravitational Waves: status, results, and prospectsPlenaryThe NANOGrav Physics Frontiers Center uses the Arecibo Observatory and the Green Bank Telescope (the two most sensitive radio telescopes in the world) to monitor very stable millisecond pulsars with very high precision. Our goal is to detect low-frequency gravitational waves and use them to learn about supermassive black-hole binaries and other gravitational-wave sources in the nanohertz band. Our access to these observatories has allowed us to reach unprecedented sensitivities, and we expect to make a detection soon. In this talk I discuss the status and prospects of our searches.
Vigeland, Sarah, Dr.Assessing the Significance of a GW Stochastic Background with the Noise-Marginalized Optimal StatisticPlenaryPulsar timing arrays (PTAs) are sensitive to the gravitational wave (GW) stochastic background from supermassive black hole binaries (SMBHBs). One method for determining the significance of a GW detection is by computing the optimal statistic, a frequentist estimator for the stochastic background amplitude. We present a technique for marginalizing the optimal statistic over the individual pulsars’ red noise parameters in order to obtain a more accurate assessment of the stochastic background amplitude and signal-to-noise ratio (SNR). We show how the noise-marginalized optimal statistic can be used to assess the significance of a GW detection by using sky scrambles and different spatial correlation relations to test whether the signal has the spatial correlations characteristic of an isotropic GW stochastic background, and we compare to similar analyses using Bayesian techniques.
Vitale, Salvatore, Prof.Black hole science with networks of future gravitational-wave detectors – a quantitative analysisPlenaryThe recent detections of gravitational waves from binary black hole coalescences suggest these sources will be observed in large number by advanced detectors. However, new instruments will be required to detect black holes at redshifts much larger than unity.
In this talk I will focus on proposed third-generation detectors, such as the Einstein Telescope and Cosmic Explorer. These instruments will detect O(10^5) events per year, and access binary black holes up to redshift of ~10. I will provide a quantitative analysis of the capabilities of networks of third-generation interferometers, focusing in particular on compact binaries.
I will also consider heterogeneous networks, accounting for the possible contribution of detectors from the previous generation, such as Voyager.
Wang, Yan, Associate ProfessorPulsar Timing Array Based Search for Supermassive Black Hole Binaries in the Square Kilometer Array EraPlenaryThe advent of next generation radio telescope facilities, such as the Square Kilometer Array (SKA), will usher in an era where a Pulsar Timing Array (PTA) based search for gravitational waves (GWs) will be able to use hundreds of well timed millisecond pulsars rather than the few dozens in existing PTAs. A realistic assessment of the performance of such an extremely large PTA must take into account the data analysis challenge posed by an exponential increase in the parameter space volume due to the large number of so-called pulsar phase parameters. We address this problem and present such an assessment for isolated supermassive black hole binary (SMBHB) searches using a SKA era PTA containing 10^3 pulsars. We find that an all-sky search will be able to confidently detect non-evolving sources with redshifted chirp mass of 10^10 M_s out to a redshift of about 28 (corresponding to a rest-frame chirp mass of 3.4 x 10^8 M_s). We discuss the important implications that the large distance reach of a SKA era PTA has on GW observations from optically identified SMBHB candidates. If no SMBHB detections occur, a highly unlikely scenario in the light of our results, the sky-averaged upper limit on strain amplitude will be improved by about three orders of magnitude over existing limits.
Weber, William JosephLISA Pathfinder: sub-femto-g differential accelerometry for gravitational wave observation from spacePlenaryLISA Pathfinder, in orbit near the L1 Lagrange point since early 2016, has demonstrated measurement of the tidal accelerations between two free-falling test masses with a precision below 10 fm/s2/Hz1/2 at frequencies between 0.1 and 60 mHz. In so doing, it demonstrates the feasibility of a high precision orbiting gravitational wave observatory like LISA. This talk presents the LPF result, the experimental evidence underpinning our physical model of the limits of free-fall, and implications for the LISA observatory.
DeCesar, MeganPulsar Searching and Timing with NANOGrav: Toward a Detection of the Gravitational-Wave BackgroundPulsar
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) pulsar timing array (PTA) is poised to detect nHz-frequency gravitational waves (GWs) within a few years to a decade, opening a window to the low-frequency end of the GW spectrum. The first detection is likely to be a stochastic GW background (GWB) from a population of coalescing supermassive black hole binaries (SMBHBs). Through precision timing of millisecond pulsars (MSPs), PTAs measure differences between the predicted and observed pulse arrival times. After accounting for noise intrinsic to the PTA, the timing residuals will display a correlated low-frequency signal in the presence of a GWB; for an isotropic GWB, this correlation is given by the Hellings-Downs curve. GWB detection with PTAs nominally requires long timing baselines (years to decades) and timing precision of order 100 ns. However, NANOGrav has reached the “intermediate regime,” where the effect of a GWB signal is comparable to that of non-GW noise sources and the SNR grows faster with the number of MSPs in the PTA than with the timing baseline. Adding more bright, stable MSPs to the array is therefore essential to decreasing the time-to-detection of the GWB, and has become the primary goal of many pulsar search campaigns. I will describe the process of pulsar timing in the context of the NANOGrav PTA, and the thus-far successful effort to add new MSPs to NANOGrav through large-scale pulsar surveys and targeted searches.
Dolch, TimNoise Budget and Interstellar Medium Mitigation in the NANOGrav Pulsar Timing ArrayPulsarGravitational wave (GW) detection with pulsar timing arrays (PTAs) requires accurate noise characterization. The noise of our galactic-scale GW detector has been systematically evaluated by the Noise Budget and Interstellar Medium Mitigation working groups within the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. Intrinsically, individual radio millisecond pulsars used by NANOGrav can have some degree of achromatic red spin noise, as well as white noise due to pulse phase jitter. Along any given line-of-sight, the ionized interstellar medium contributes chromatic noise through dispersion measure (DM) variations, interstellar scintillation (ISS), and scattering. These effects contain both red and white components. For future wideband receivers, we also expect frequency-dependent DMs. Pulse profile evolution with radio frequency can interact with ISS to give timing errors in wideband receivers. Having anticipated and measured these diverse sources of detector noise, the NANOGrav PTA remains well-poised to detect low-frequency GWs.
Mihaylov, Deyan, MrProbing alternative gravitational wave polarisations with GaiaPulsarThe Gaia mission offers new possibilities for detecting and studying gravitational waves (GWs) through astrometry, analogous in many ways to the pulsar timing technique. Modified theories of gravity predict up to 6 GW degrees of freedom which can propagate according to a massive or massless wave equation. Current ground-based detectors currently struggle to disentangle these different polarisations due to the two LIGO detectors being nearly (anti-)aligned with one another. In contrast, the astrometric deflection pattern caused by each polarisation state is strikingly distinct and depends on the mass of that mode. In this talk, I will explore the constraints which Gaia would be able to place on additional polarisation states and their masses.
Berger, Beverly K., Dr.Tracking down the origins of Advanced LIGO noise: some examplesSearch 1On the way toward Advanced LIGO's reaching design sensitivity, various sources of instrumental and environmental noise must be identified and ameliorated. Here we discuss efforts to understand the origin of noise manifested as bursts (glitches) and/or range-impacting features at LIGO Hanford. Advanced LIGO monitors thousands of channels in addition to the gravitational wave channel h(t). These channels can be studied to find correlations between instrumental or environmental sensor signals and the gravitational wave channel. Several examples found at LIGO Hanford Observatory in O1 and O2 will be discussed as time permits including the 50 Hz glitches traced to an air compressor, the 1083 Hz glitches not due to the calibration line at that frequency, peculiar features in the h(t) spectrogram found to be caused by a ringing phone, airplane glitches, and the 5 am Pacific-time truck-traffic range drop.
Gadre BhooshanHierarchical search strategies for compact binary coalescences using aligned-spin waveformsSearch 1The current template-based searches for gravitational waves from coalescing compact binaries in the data from LIGO-like detectors use waveform models in which total and orbital angular momenta are parallel to each other. Even with these aligned-spin models over the restricted parameter space, one has to use a bank containing few millions of waveforms to filter out the signal from the noisy data. The search is already computationally expensive. A similar search with larger parameter space, better statistic and with longer waveforms with improved detectors will be even more costlier computationally and with more potential triggers to follow. Moreover, searches for precessing binaries are currently computationally prohibitive. To reduce the computational cost of the current searches, we have extended the two-stage hierarchical technique previously developed for non-spinning waveforms with aligned-spin banks incorporating coincidences and vetoes at each stage. On simulated data, we manage to reduce the computational cost by more than an order of magnitude while recovering all the signals detectable by the standard flat coincidence search. Even for real data, we expect the seach to speed up is by a factor of few. We are also trying to introduce a
simple cross-correlation step to prioritize analysis of those chunks of the data which are more likely to contain detectable gravitational signals,
to further enhance the efficiency of the search.
Wen, LinqingBinary Black Hole Merger with An Accreting CompanionSearch 1We propose a class of binary black hole mergers within hierarchical triples, where a high-mass star in the outer orbit is accreting onto an inner binary composed of a pair of coalescing black holes. We show that the accretion flow could possibly drive the inner binary to merge much faster than it would purely due to gravitational radiation. We argue that this could greatly enhance the event rate of these binary mergers, making it a potentially important source of gravitational waves(GWs). Such accretion-driven binary black hole mergers are particularly interesting from an electromagnetic point of view. The binary black hole mergers are expected to be associated with relativistic matter outflows, with enhanced bolometric outbursts during the final merger. The inspiral phase of these binary black holes could be detectable by eLISA a few years before they enter the LIGO band. The presence of the third body could possibly be identified from gravitational waves alone due to the acceleration of the inner binary by the 3rd star. In this talk, I will present the details of this model and discuss its implications to the multi-messenger observations of binary black hole merger.
Barone, Fabrizio, ProfessorA new class of compact high sensitive TILTMETERS based on the UNISA folded pendulum mechanical architectureSeismicWe present the Extended Folded Pendulum Model (EFPM), a model developed for a quantitative description of the dynamical behavior of a folded pendulum generically oriented in space, with horizontal and vertical folded pendulums as limit cases. This model, based on the Tait-Bryan angular reference system, highlights the relationship between the folded pendulum orientation, referred to the direction of the gravitational acceleration, and its natural resonance frequency, that is the key for its configuration as a stand-alone tiltmeter. This result, confirmed by the tests performed with a monolithic UNISA Folded Pendulum, opens the way to new interesting applications of the folded pendulum as tiltmeter.
Frajuca, Carlos, Dr.Schenberg microwave cabling seismic isolationSeismicSchenberg is a detector of gravitational waves resonant mass type, with a central frequency of operation of 3200 Hz. Transducers located on the surface of the resonating sphere, according to a distribution half-dodecahedron, are used to monitor a strain amplitude. Such transducers are parametric and makes use of a microwave cavity to measure the displacements of the sphere surface, then a microwave cable must reach a place close to the sphere surface. The objective of this work is to study the seismic isolation of such cabling, analysing the deformation noise curve obtained by finite element modeling (FEM) of a seismic noise induced in one end of the cabling and compared it to the resulting vibration in another end of the cabling. The result shows an attenuation of 390 dB, enough to allow the detector to work properly. This result can be applied in other future detectors.
Köhlenbeck, SinaStabilization of a suspended test cavity for the SQL Interferometer at the AEI 10m PrototypeSeismicAt the AEI 10m Prototype a quantum noise limited interferometer will be set up, to probe the standard quantum limit and serve as a test bed for future gravitational wave detectors.
To be able to prepare the infrastructure and the stabilization schemes required for the final SQL interferometer, a 10m long Fabry–Pérot cavity is set up. The "single arm test" is using two mirrors with equivalent radius of curvature and finesse of the arm cavities of the final interferometer. The mirrors are suspended by triple suspension, developed with the University of Glasgow. We present the current status and the initial lock, achieved with the suspension actuators including a plate capacitor electro static drive.
Lackey, Benjamin, PostdocConstructing surrogate models of inspiraling binary neutron star systems with spin and tidesSource 2Fast and accurate waveform models are necessary for measuring properties of inspiraling binary neutron star systems such as the masses, spins, and equation-of-state-dependent tidal parameters. Effective one body (EOB) waveforms that are accurate enough to avoid significant biases take over 10 minutes to evaluate, and this is too slow for parameter estimation codes that require 10^7--10^8 waveform evaluations. I will discuss a method for constructing a frequency-domain surrogate model that is 10^4 times faster and accurately reproduces the EOB waveforms for the 5-dimensional parameter space that includes mass ratio, aligned-spin, and tides. We use Gaussian process regression and active learning to optimally sample the parameter space and construct a surrogate with approximately 500 waveforms instead of the 10^6 waveforms that would be required with standard interpolation methods. Finally, I will show how this same method can be used to optimally choose parameters for numerical relativity simulations to correct the the EOB surrogate during the last several orbits and merger.
Scheel, Mark, Dr.Numerical relativity in the era of gravitational-wave observationsSource 2Numerical relativity---the direct solution of Einstein's equations for relativistic systems---allows accurate computation of the gravitational waves expected from general relativity. I describe the status of numerical-relativity simulations of binary black-hole systems, including their current strengths and limitations. I describe how these simulations have been used to better understand observed gravitational-wave sources.
Sennett, Noah, Mr.Distinguishing Boson Stars from Black Holes and Neutron Stars with Tidal InteractionsSource 2Binary systems containing boson stars---self-gravitating configurations of a complex scalar field---can potentially mimic black holes or neutron stars as gravitational-wave sources. We investigate the extent to which tidal effects in the gravitational-wave signal can be used to discriminate between these standard sources and boson stars. First, we compute the tidal deformability parameter characterizing the dominant tidal imprint in the gravitational-wave signals for two boson star models. Employing a Fisher matrix analysis, we estimate the precision with which Advanced LIGO and third-generation detectors can measure these tidal parameters using the inspiral portion of the signal. We discuss a novel strategy to improve the distinguishability between black holes/neutrons stars and boson stars by combining tidal deformability measurements of each compact object in a binary system, thereby eliminating the scaling ambiguities in each boson star model. Our analysis suggests that current-generation detectors can potentially distinguish certain models of boson stars from black holes, as well as from neutron-star binaries if they have either a large total mass or a large (asymmetric) mass ratio. Discriminating very compact boson stars from black holes using only tidal effects will be difficult with Advanced LIGO, but third-generation detectors should be able to distinguish between binary black holes and these binary boson stars.
Pannarale, Francesco, Dr.Frequency Domain Binary Black Hole Gravitational Waveforms with Higher MultipolesSource1This talk discusses a general method for estimating contributions to gravitational-wave signals from non-precessing black hole binaries beyond the leading quadrupole order. The method is based on the stationary phase approximation, and it uses the Kerr quasi-normal mode spectrum and phenomenological observations in order to extend known relationships between gravitational multipoles. This method is applied to an existing leading quadrupole order frequency-domain waveform model tuned to Numerical Relativity (known as PhenomD) in order to yield a higher multipole inspiral-merger-ringdown gravitational-wave model. I analyze the performance of this model in terms of mismatches against numerical simulations of binary black hole mergers, and I illustrate examples of its use in parameter estimation.
Yang, Huan, Dr.General-Relativistic Dynamics of an Extreme Mass-Ratio Binary with an External BodySource1We study the dynamics of a hierarchical three-body system in the general-relativistic regime: an extreme mass-ratio inner binary under the tidal influence of an external body. The inner binary consists of a central Schwarzschild black hole and a test body moving around it. We discover three types of tidal effects on the orbit of the test body. First, the angular moment of the inner binary precesses around the angular momentum of the outer binary. Second, the tidal field drives a ``transient resonance" when the radial and azimuthal frequencies are commensurable. In contrast with resonances driven by the gravitational self-force, this tidal-driven resonance may boost the orbital angular momentum.
Finally, as an orbit-dynamical effect during the non-resonant phase, we calculate the correction to the Innermost Stable Circular (mean) Orbit due to the tidal interaction. Hierarchical three-body systems are potential sources for future space-based gravitational wave missions and the tidal effects that we find could contribute significantly to their waveform.
Yang, Huan, Dr.Gravitational wave spectroscopy of compact binary merger remnants via mode stackingSource1I will review our recent developments on coherent mode stacking method, designed to enhance the detectability of oscillations of compact-binary merger remnants - black holes or hyper-massive neutron stars. I will compare the detection rate with or without this coherent stacking method, which is also compared with commonly used Bayesian approach (using the product of Bayes factors from different events).
Fernández Barranco, GermánPhotoreceivers in intersatellite laser interferometrySpace 1The particular conditions present in intersatellite laser interferometers, like the space-borne gravitational wave detector LISA, set challenging requirements for the opto-electrical interface of the system, the photoreceiver (PR). Low noise, high speed electronics are needed to detect optical beat notes with pW amplitudes in the MHz frequency range. We present the design and characterization of the PR developed for the GRACE-FO mission, as well as the first experimental results of a PR design based on discrete heterojunction bipolar transistors. The input-referred current noise of this transistor-based design is below 2 pA/sqrt(Hz) up to 30 MHz. Furthermore, simulations of the effect of non-uniform photodiode responses on the interferometer output have been conducted to study their influence on observables such as differential wavefront sensing and longitudinal phase.
Penkert, DanielUltra-stable fiber injectors for rapid development cyclesSpace 1The development of LISA technology requires state-of-the-art laser interferometry test beds with picometer pathlength stability, on the one hand, but rapid development cycles with moderate cost factors, on the other. Due to their inherent complexity, quasi-monolithic fiber injectors—so-called fiber injector optical subassemblies (FIOSs)—constitute one of the most challenging components in these respects. Here, we present a new breed of thermally compensated FIOS as a well-balanced compromise of all of the above aspects along with two use cases: LISA prototype phasemeter technology is being tested and improved upon by means of our “Hexagon” interferometer, whereas our 3-backlink interferometer will be key to investigating and directly comparing several competing realizations of an optical backlink between a LISA spacecraft's two optical benches. Furthermore, a future expansion stage of the “Hexagon” setup will be able to simulate the full LISA arm metrology chain, including inter-spacecraft clock tone transfer, PSN ranging, and data communication.
Schwarze, Thomas, Mr.Phase extraction for LISA heterodyne interferometry and deep frequency modulation interferometrySpace 1We present the investigation on phase extraction algorithms and hardware (aka phasemeters) for two interferometer techniques applicable to track test masses in the context of gravitational wave astronomy. The first is heterodyne interferometry for LISA, which aims to measure with microcycle/sqrt(Hz) precision at frequencies between 0.1 mHz and 1 Hz using MHz heterodyne frequencies. Due to the lack of a proper reference, verifying the required phase performance and linearity with high dynamic range is not staight-forward. A unique optical testbed was set up to approach the problem. Here we show its results testing a LISA phasemeter developed within an ESA contract.
The second technique, deep frequency modulation interferometry, encodes the
measurement phase in several complex harmonic amplitudes of the modulation frequency. We present the development and results of methods to extract the phase from this signal.
Dolesi, Rita, Prof.Brownian noise and other stray forces introduced by residual gas surrounding geodesic reference masses: the experience of LISA PathfinderSpace 2The presence of gas surrounding the nominally free falling test masses of space-based gravitational waves detectors introduces stray forces through several mechanism including the gas damping Brownian noise. We present here the investigations of these effects performed on board of LISA Pathfinder and the consequent recommendation for LISA.
Gerberding, Oliver, Dr.A phase reference for LISA: Suppressing ghost beams in classic heterodyne interferometrySpace 2The space-based gravitational wave detector LISA uses heterodyne laser interferometry to measure the displacement between free floating test masses about 2 million kilometer apart. To achieve the desired strain sensitivity on the order of 10^(-20)Hz/sqrt(Hz) at frequencies between 0.1 mHz and 1 Hz the interferometry needs to accommodate the orbital dynamics of the LISA constellation, which, amongst other effects, includes a variation of the angles in the equilateral triangle between the three spacecraft of about 1.5°. Assuming one implements two separate and moving optical subassemblies within each S/C this angle variation can be compensated. However, the nature of the LISA metrology requires a precise reciprocal phase reference between both assemblies to enable a subtraction of laser frequency noise. Previous experiments have studied the use of optical fibers to implement this so-called “backlink”, revealing that the required levels of 6 urad/sqrt(Hz) for the fiber reciprocity could be achieved, but only after applying a number of additional stabilizations and balanced detection to reduce the influence of parasitic ghost beams generated within the fibers. We discuss the phase measurement limitations due to ghost beams and show the current status of our experimental efforts to test three alternative backlink implementations within a single set-up. This also includes a discussion of other possible backlink layouts and the construction of two quasi-monolithic optical benches.
Isleif, Katharina-Sophie, M.Sc.Upscalable optical test mass readout via deep frequency modulation interferometrySpace 2The LISA Pathfinder mission has shown that the motion of free floating test masses can be measured with high precision by using heterodyne interferometry. Future geodesy satellite missions with multiple test masses also aim to use optical multi-degree of freedom readout to improve the sensitivity of detecting the Earth's gravitational field. Since the LISA Pathfinder scheme is not easily upscalable we are investigating alternative interferometer techniques. Deep frequency modulation (DFM) is an intrinsic self-homodyning technique that produces a quasi-heterodyne interference signal with a high dynamic range readout. It is a promising candidate for simplifying optical set-ups, for achieving LISA-like displacement sensitivities and for measuring absolute distances.
We will introduce the DFM technique and the experimental results of a small quasi-monolithic unequal arm length Mach-Zehnder interferometer. The interferometers has also been indicated as a suitable laser frequency reference for LISA. We achieved a frequency noise level of 100 Hz/rt(Hz) at 1 Hz by locking a diode laser to it via balanced DC readout.
With regard to the compact interferometers, referred to as optical heads, we designed a single, self-interfering, optical component that implements all required beamsplitters in one component. To probe the performance of DFM we are setting up an experiment where we measure the intentional motion of a double-sided gold coated mirror from both directions.
Kawazoe, Fumiko, Dr.Structured Doctoral Education in Hannover - Joint Program between IMPRS-GW and geo-Q RTGSpace 3
Starting 2015 we started to form joint programs between our structured doctoral education programs, the International Max Planck Research School (IMPRS) on Gravitational Wave Astronomy and geo-Q Research Training Group (RTG). We have also expanded our activities to include GEO collaboration-wide activities, such as our joint Lecture Week in June in Scotland between International Max Planck Partnership (IMPP) with Glasgow University and IMPRS. The brilliant feedback from our participants encouraged us to organize another joint Lecture Week with the Glasgow team, this time with IMPRS and also geo-Q RTG. We have learned that expanded joint programs reduces the teaching effort at the same time optiizes the learning process. I would like to discuss the possibility of joining school activities in the LSC community.
Paczkowski, SarahLISA Pathfinder: Optical Metrology System Noise SourcesSpace 3On LISA Pathfinder, the local interferometry measurement relevant for LISA has been tested and has shown excellent performance. To understand the measured noise level, several experiments have been performed to characterise the possible noise sources and their couplings. This is essential for future interferometer development.

Three possible contributions to the readout noise of the two main test mass interferometer longitudinal measurements in the LISA Pathfinder optical metrology system (OMS) are discussed in this talk. One results from the laser frequency noise. It is minimised by stabilising the laser frequency with a dedicated control loop. A similar control loop, the so-called OPD loop, suppresses phase noise arising from disturbances of the two optical fibres and the so-called small vector noise. A third possible noise contribution, whose coupling is minimised by the test mass position commanded, is relative intensity noise (RIN). For LISA, the OMS performance along the angular degrees of freedom is also important. In LISA Pathfinder, two rotations of each test mass are measured using differential wavefront sensing (DWS). Experiments have been performed to understand how some of the aforementioned noise sources contribute to the DWS performance.

In this talk, we summarise the results of the experiments carried out to characterise each of these possible contributions to the remaining low OMS noise level.
Gibert, FerranTemperature noise effects on LISA Pathfinder's Gravitational Reference Sensors: preliminary resultsSpace 4Temperature noise in the Gravitational Reference Sensors (GRS) of LISA Pathfinder induces stray forces on the test masses, produced either by absolute temperature fluctuations or by temperature gradient noise. Such effects have been studied on board through dedicated thermal experiments, identifying sources of the order ~10pN/K per mass for the temperature gradients and ~1pN/K for the average temperature fluctuations, both amounts decaying with time. Here we will present the preliminary results obtained and discuss their consequences for LISA.
Russano GiulianaMeasurements of subfemto-g acceleration noise with parabolic flights in pico-g for space-based gravitational wave observatory: LISA Pathfinder Free-fall Experiment ResultsSpace 4The LISA Pathfinder geodesic explorer mission has tested the key experimental concept for the future LISA gravitational wave observatory, measuring a residual acceleration between two free falling test masses orbiting in the same apparatus at sub-femto-m/s^2Hz^1/2 level at frequency down to 0.1 mHz.
We report on the implementation and results of the on-board free-fall experiment, in which the compensation of the gravitational imbalance between the two free-falling objects, that is performed by forcing electrostatically one of them to be at average constant distance from the other, is limited only to brief periodic impulses, with test masses free to move in between two “kicks”. The actuation-free motion is then analysed for the remaining sources of acceleration noise below the repetition frequency of the experiment (~3 mHz).
This control method is an alternative to the standard operations control loop, where the balance force is applied continuously, and therefore allows to test a LISA-like actuation configuration, free from the actuator noise and its force calibration.
Spero, Robert, Dr.Flight Phasemeter on the Laser Ranging Interferometer on the GRACE Follow-On MissionSpace 4We describe an inter-spacecraft laser interferometry technology demonstrator with similarities to LISA. Functions relevant to LISA that will be implemented in flight include phase tracking, differential wavefront sensing and control, laser phase locking, and laser frequency stabilization.
Ghosh, Joyee, Dr.Waveguide-based squeezed light source @ 1.55-2.1 µm for quantum noise reduction in next generation GWD
Two major sources of noise that currently limit the performance of GWDs are the thermal noise in the mirror coating and the quantum noise of light. The latter comprises of shot noise and radiation pressure noise. Shot noise contribution to GW strain measurement is independent of frequency. But radiation pressure noise is frequency-dependent and arises due to vacuum fluctuations entering the interferometer through a port of the beam splitter, causing test masses to fluctuate. While shot noise can be reduced by using high power circulating in the Fabry-Perot cavity arms of interferometer, radiation pressure noise is inevitable due to quantum vacuum state of light. One way to mitigate the effect of quantum vacuum in GWD and improve its sensitivity is by injecting squeezed light. This quantum feature can lead to a factor of three improvement in next upgrade of the LIGO detector. So far, the best noise suppression is achieved with squeezing at 1064 nm. However, as silicon is a promising alternative material for future upgrades to existing/third generation GWD mirror substrates, owing to a reduction in the thermal displacement noise, it is important to investigate squeezed light sources in the wavelength range of 1.55-2.1 µm in which silicon is transparent. We plan to study and explore waveguide-based squeezed light sources in the above range. A waveguide-based squeezer is interesting owing to its compactness and tight confinement of modes enhancing the nonlinear interaction.
Leonardi, Matteo, Dr.Status of the squeezed-light application at GEO 600
The GEO 600 gravitational wave detector has been continuously and successfully using a squeezed light source to improve its sensitivity since 2010, paving the way for squeezer integration in the advanced detector era. We report on the history and progress of the AEI squeezer integration into GEO.
Mansell, Georgia, MissDevelopment of a squeezed light source at 2 micron
The proposed LIGO Voyager upgrade consists of an interferometer operating at a wavelength in the 2 micron region. The design also features frequency-dependent squeezing for broadband quantum noise reduction.

We will present the first squeezed light results in the 2 micron region. Our experiment uses a frequency stabilised commercial thulium fibre laser operating at 1984 nm. This is frequency doubled to 992 nm which pumps the squeezer optical parametric oscillator (OPO). The squeezed vacuum is measured using balanced homodyne detection with a bright local oscillator. Thus far 0.5 dB have been measured in preliminary experiments.

The OPO consists of a doubly resonant bowtie cavity with a wedged PPKTP crystal as the nonlinear medium, and follows the design of previous ANU squeezers. The bowtie geometry provides isolation from backscattered light.

We will discuss the design considerations of the laser source, optical layout and OPO cavity parameters. We aim to ultimately produce 11dB of squeezing, and measure 5dB of squeezing, with this discrepancy dominated by the quantum defect of easily available photodiodes for the homodyne detector.
Ain, Anirban, Mr.Efficient mapmaking of the stochastic gravitational wave backgroundStoch/CWGravitational waves from the early universe and unresolved astrophysical sources are expected to create a stochastic GW background (SGWB). Radiometric techniques are used to make upper-limit maps of an anisotropic SGWB by cross-correlating data from pairs of detectors. We have developed algorithms to perform this analysis in a highly efficient way. We fold the cross-spectral density of data from pairs of detectors, the core dataset for a radiometer search, for a whole observation run to one sidereal day's data, providing enormous data compression and computational speed-up. To take full advantage of folded data and to make use of the well-known HEALPix pixelisation and tools, we have developed a new code called PyStoch. PyStoch incorporates tools healpy packages and some more computational tricks that give a factor of few speed-up. Folding and PyStoch together has made it possible to perform radiometer mapmaking in just a few minutes on a typical laptop. Moreover, PyStoch generates skymaps at every frequency bins as an intermediate data product. We hope that these techniques will make stochastic analysis very convenient and enable searches, e.g., blind narrowband search, which were not feasible so far due to computational limitations.
Okounkova, MariaNumerical binary black hole mergers in dynamical Chern-SimonsStoch/CWTesting general relativity in the non-linear, dynamical, strong-field regime of gravity is one of the major goals of gravitational wave astrophysics. Performing precision tests of general relativity (GR) requires numerical inspiral, merger, and ringdown waveforms for binary black hole (BBH) systems in theories beyond GR. Currently, GR and scalar-tensor gravity are the only theories amenable to numerical simulations. In this article, we present a well-posed perturbation scheme for numerically integrating beyond-GR theories that have a continuous limit to GR. We demonstrate this scheme by simulating BBH mergers in dynamical Chern-Simons gravity (dCS), to linear order in the perturbation parameter. We present mode waveforms and energy fluxes of the dCS pseudoscalar field from our numerical simulations. We find good agreement with analytic predictions at early times, including the absence of pseudoscalar dipole radiation. We discover new phenomenology only accessible through numerics: a burst of dipole radiation during merger. We also quantify the self-consistency of the perturbation scheme. Finally, we estimate bounds that GR-consistent LIGO
detections could place on the new dCS length scale, approximately $l \lesssim \mathcal{O}(10)$ km.
Matas, Andrew, Dr.Searches for the Stochastic Gravitational Background from LIGOs First Observing RunStoch/CWThe stochastic gravitational wave background is made of an incoherent superposition of astrophysical and cosmological sources. After reviewing the data analysis strategy used to search for the stochastic background using ground-based interferometers, I will present search results from Advanced LIGOs first observing run. While no stochastic background was detected, we can place upper limits on the energy density in the background. Assuming an isotropic stochastic background with a constant energy density spectrum, the upper limit on the energy density in the stochastic background is Omega_GW < 1.7e-7 at 95% confidence, which is a factor of 33 improvement on limits from Initial LIGO-Virgo. I will also present sky maps showing upper limits on anisotropic contributions to the stochastic background using the spherical harmonic and broadband radiometer methods. Finally, using the radiometer method I will present narrowband limits from three promising sky directions for gravitational wave sources: the galactic center, the low mass X-ray binary Scorpius X-1, and Supernova 1987A.
Kumar, Rahul, DrCryogenic sapphire mirror suspension system for KAGRA detectorSuspensionKAGRA detector is a 2nd generation, Large-scale Cryogenic Gravitational Wave Telescope (LCGT), currently being built in Japan for the detection of gravitational wave signals. The arm-length of the interferometer is 3 km and is located 200 m underground in the Kamioka mine. KAGRA is a cryogenic temperature detector i.e. the mirror and its multistage suspensions called cryogenic payload will be cooled to 20K to reduce thermal noise. The use of sapphire (Al2O3) as a substrate material for the suspension system is the baseline design for the KAGRA detector. In this talk, I will present the design, fabrication and characterization of the cryogenic sapphire mirror suspension system for KAGRA. This will include sapphire fibre installation and welding procedures to suspend 23 kg sapphire test mass mirror. I will talk about the results of the cool down test, especially thermal conductivity at cryogenic temperature. I will also present the results of materials research (mechanical strength of metals and bond layers) at cryogenic temperature.
Naticchioni, Luca, Dr.The payloads of Advanced Virgo: current status and upgradesSuspensionIn this talk I will give an overview of the payloads currently installed in Advanced Virgo, describing their mechanical structure and
performances using the steel-wire suspension of mirrors. Then I will show the upgrade that we will introduce in the monolithic payloads after
O2 to shield the fused silica fibers from vacuum contaminations. I will also summarize the optical lever setup deployed for the control of the
AdV payloads' suspended elements.
Travasso, Flavio, Dr.Status of the Monolithic Suspensions for Advanced VirgoSuspensionThe monolithic suspensions are the most important upgrade for the GW advanced detectors. They will be reinstalled in Virgo in the
next future before O3. Indeed this implementation is crucial to reach the nominal sensitivity of Advanced Virgo. Due to the failures experienced during the installation phase, a strong effort has been put in place to find the causes. In the present work, I will give a quick overview of the failures and the tests performed on the fibers and the anchors: the result is that the failures of the monolithic suspensions were not due to an inherent weakness of the design, but were rather the consequence of an external event. A deeper investigation showed that the failures were caused by contaminants in the vacuum system. The tests and analysis performed are described and the results discussed.