55218371
Brownian force noise from molecular collisions and the sensitivity of advanced gravitational wave observatories
We present an analysis of Brownian force noise from residual gas damping of reference test masses as a fundamental sensitivity limit in small force experiments. The resulting acceleration noise increases significantly when the distance of the test mass to the surrounding experimental apparatus is smaller than the dimension of the test mass itself. For the Advanced LIGO interferometric gravitational wave observatory, where the relevant test mass is a suspended 340 mm diameter cylindrical end mirror, the force noise power is increased by roughly a factor 40 by the presence of a similarly shaped reaction mass at a nominal separation of 5 mm. The force noise, of order 20 fN\rthz\ for $2 \times 10^{-6}$ Pa of residual H$_2$ gas, rivals quantum optical fluctuations as the dominant noise source between 10 and 30 Hz. We present here a numerical and analytical analysis for the gas damping force noise for Advanced LIGO, backed up by experimental evidence from several recent measurements. Finally, we discuss the impact of residual gas damping on the gravitational wave sensitivity and possible mitigation strategies.
123492651
Axion to magnon conversion. A scheme for the detection of galactic axions
Abstract We consider the possibility of detecting axions in the halo of our Galaxy by means of converting them into collective excitations of a ferromagnet. We calculate that, under optimal conditions, one can convert about 6000 axions per day in a 1 m 3 ferromagnet. The signal has an intrinsic diurnal modulation of order unit due to the combined effect of Earth rotation and motion of the solar system with respect to the galactic center. We discuss the ultimate limitations arising from thermal fluctuations of the magnetization.
63844509
The LISA Pathfinder interferometry-hardware and system testing
Preparations for the LISA Pathfinder mission have reached an exciting stage. Tests of the engineering model (EM) of the optical metrology system have recently been completed at the Albert Einstein Institute, Hannover, and flight model tests are now underway. Significantly, they represent the first complete integration and testing of the space-qualified hardware and are the first tests on an optical system level. The results and test procedures of these campaigns will be utilized directly in the ground-based flight hardware tests, and subsequently during in-flight operations. In addition, they allow valuable testing of the data analysis methods using the MATLAB-based LTP data analysis toolbox. This paper presents an overview of the results from the EM test campaign that was successfully completed in December 2009.
120934985
Technology of free fall for LISA
In this paper we discuss the status of technology for achieving free fall of test-masses for LISA. The main part of this effort consists of developing an inertial sensor with parasitic force isolation better than 10−15 N/√Hz at 0.1 mHz, and residual coupling of test-mass to spacecraft with stiffness less than 10−7 N/m. We also briefly report on experiments to test sensor performances on ground and in space.
118380507
Data Analysis for Resonant Gravitational Wave Antennae: Internal Vetoes by c2 Like Test
120641812
Progress in the development of a position sensor for LISA drag-free control
We report on progress in the development of free-falling moving test-masses for LISA and for the related technology demonstration mission. We present simple formulae to evaluate the performance of the device as a function of the various design parameters, and we compare them with preliminary experimental results from a test prototype we are developing. Quantitative agreement is found. Finally, we present a control law, along with a performance simulation, for low-frequency electrostatic suspension of the test-mass with minimal perturbation of the motion within the measuring frequency band.
119108663
Effect of calibration errors on Bayesian parameter estimation for gravitational wave signals from inspiral binary systems in the advanced detectors era
By 2015 the advanced versions of the gravitational-wave detectors Virgo and LIGO will be online. They will collect data in coincidence with enough sensitivity to potentially deliver multiple detections of gravitation waves from inspirals of compact-object binaries. This work is focused on understanding the effects introduced by uncertainties in the calibration of the interferometers. We consider plausible calibration errors based on estimates obtained during LIGO’s fifth and Virgo’s third science runs, which include frequency-dependent amplitude errors of 
∼ 
10 
% 
 and frequency-dependent phase errors of 
∼ 
3 
  
  
degrees 
 in each instrument. We quantify the consequences of such errors estimating the parameters of inspiraling binaries. We find that the systematics introduced by calibration errors on the inferred values of the chirp mass and mass ratio are smaller than 20% of the statistical measurement uncertainties in parameter estimation for 90% of signals in our mock catalog. Meanwhile, the calibration-induced systematics in the inferred sky location of the signal are smaller than 
∼ 
50 
% 
 of the statistical uncertainty. We thus conclude that calibration-induced errors at this level are not a significant detriment to accurate parameter estimation.
17415632
Approximate solutions in General Relativity via deformation of embeddings
A systematic study of deformations of four-dimensional Einsteinian space-times embedded in a pseudo-Euclidean space E N of higher dimension is presented. Infinitesimal deformations, seen as vector fields in E N , can be divided in two parts, tangent to the embedded hypersurface and orthogonal to it; only the second ones are relevant, the tangent ones being equivalent to coordinate transformations in the embedded manifold. The geometrical quantities can be then expressed in terms of embedding functions z A and their infinitesimal deformations v A z A → ˜ z A = z A + e v A . The deformations are called Einsteinian if they keep Einstein equations satisfied up to a given order in e. The system so obtained is then analyzed in particular in the case of the Schwarzschild metric taken as the starting point, and some solutions of the first-order deformation of Einstein’s equations are found. We discuss also second and third order deformations leading to wave-like solutions and to the departure from spherical symmetry towards an axial one (the approximate Kerr solution) 1
9403518
Measuring the spin of black holes in binary systems using gravitational waves.
Compact binary coalescences are the most promising sources of gravitational waves (GWs) for ground-based detectors. Binary systems containing one or two spinning black holes are particularly interesting due to spin-orbit (and eventual spin-spin) interactions and the opportunity of measuring spins directly through GW observations. In this Letter, we analyze simulated signals emitted by spinning binaries with several values of masses, spins, orientations, and signal-to-noise ratios, as detected by an advanced LIGO-Virgo network. We find that for moderate or high signal-to-noise ratio the spin magnitudes can be estimated with errors of a few percent (5%-30%) for neutron star-black hole (black hole-black hole) systems. Spins' tilt angle can be estimated with errors of 0.04 rad in the best cases, but typical values will be above 0.1 rad. Errors will be larger for signals barely above the threshold for detection. The difference in the azimuth angles of the spins, which may be used to check if spins are locked into resonant configurations, cannot be constrained. We observe that the best performances are obtained when the line of sight is perpendicular to the system's total angular momentum and that a sudden change of behavior occurs when a system is observed from angles such that the plane of the orbit can be seen both from above and below during the time the signal is in band. This study suggests that direct measurement of black hole spin by means of GWs can be as precise as what can be obtained from x-ray binaries.
122803437
Effect of calibration errors on Bayesian parameter estimation for gravitational wave signals from inspiral binary systems in the advanced detectors era: Further investigations
By 2015, the advanced versions of the gravitational wave detectors Virgo and LIGO will be online. They will collect data in coincidence with enough sensitivity to potentially deliver multiple detections of gravitational waves from inspirals of compact-object binaries. In a previous work, we have studied the effects introduced in the estimation of the physical parameters of the source by uncertainties in the calibration of the interferometers. Our bias estimator for parameter errors introduced by calibration uncertainties consisted of two terms: A genuine bias due to the calibration errors, and a contribution coming from the limited number of samples used to explore the parameter space. In this article, we have focused on this second term, and we have shown how it is smaller than the former (about 10 times smaller), and how it decreases as the signal-to-noise ratio increases.
118465419
Parameter estimation from gravitational waves generated by nonspinning binary black holes with laser interferometers: Beyond the Fisher information
In this paper we apply to gravitational waves from nonspinning binary systems a recently introduced frequentist methodology to calculate analytically the error for a maximum likelihood estimate of physical parameters. While existing literature focuses on using the Cramer Rao Lower bound and Monte Carlo simulations, we use a power expansion of the bias and covariance in inverse powers of the signal to noise ratio. The use of higher order derivatives of the likelihood function in the expansions makes the prediction also sensitive to the secondary lobes of the maximum likelihood estimate probability distribution. We discuss conditions for validity of the Cramer Rao Lower bound and predict new features in regions of the parameter space currently not explored. For example, we see how the bias can become the most important contributor to the parameters' errors for high mass systems (200M(circle dot) and above).