Time-domain modelling of Extreme-Mass-Ratio Inspirals for the Laser Interferometer Space Antenna

When a stellar-mass compact object is captured by a supermassive black hole located in a galactic centre, the system losses energy and angular momentum by the emission of gravitational waves. Subsequently, the stellar compact object evolves inspiraling until plunging onto the massive black hole. These EMRI systems are expected to be one of the main sources of gravitational waves for the future space-based Laser Interferometer Space Antenna (LISA). However, the detection of EMRI signals will require of very accurate theoretical templates taking into account the gravitational self-force, which is the responsible of the stellar-compact object inspiral. Due to its potential applicability on EMRIs, the obtention of an efficient method to compute the scalar self-force acting on a point-like particle orbiting around a massive black hole is being object of increasing interest. We present here a review of our time-domain numerical technique to compute the self-force acting on a point-like particle and we show its suitability to deal with both circular and eccentric orbits.Comment: 4 pages, 2 figures, JPCS latex style. Submitted to JPCS (special issue for the proceedings of the Spanish Relativity Meeting (ERE2010)

Testing Chern-Simons modified gravity with observations of extreme-mass-ratio binaries

Extreme-Mass-Ratio Inspirals (EMRIs) are one of the most promising sources of gravitational waves (GWs) for space-based detectors like the Laser Interferometer Space Antenna (LISA). EMRIs consist of a compact stellar object orbiting around a massive black hole (MBH). Since EMRI signals are expected to be long lasting (containing of the order of hundred thousand cycles), they will encode the structure of the MBH gravitational potential in a precise way such that features depending on the theory of gravity governing the system may be distinguished. That is, EMRI signals may be used to test gravity and the geometry of black holes. However, the development of a practical methodology for computing the generation and propagation of GWs from EMRIs in theories of gravity different than General Relativity (GR) has only recently begun. In this paper, we present a parameter estimation study of EMRIs in a particular modification of GR, which is described by a four-dimensional Chern-Simons (CS) gravitational term. We focus on determining to what extent a space-based GW observatory like LISA could distinguish between GR and CS gravity through the detection of GWs from EMRIs.Comment: 10 pages, JPCS of the Amaldi 9 and NRDA 201

Are Time-Domain Self-Force Calculations Contaminated by Jost Solutions?

The calculation of the self force in the modeling of the gravitational-wave emission from extreme-mass-ratio binaries is a challenging task. Here we address the question of the possible emergence of a persistent spurious solution in time-domain schemes, referred to as a {\em Jost junk solution} in the literature, that may contaminate self force calculations. Previous studies suggested that Jost solutions are due to the use of zero initial data, which is inconsistent with the singular sources associated with the small object, described as a point mass. However, in this work we show that the specific origin is an inconsistency in the translation of the singular sources into jump conditions. More importantly, we identify the correct implementation of the sources at late times as the sufficient condition guaranteeing the absence of Jost junk solutions.Comment: RevTeX. 5 pages, 2 figures. Version updated to match the contents of the published articl

Gravitational wave parameter estimation with compressed likelihood evaluations

One of the main bottlenecks in gravitational wave (GW) astronomy is the high cost of performing parameter estimation and GW searches on the fly. We propose a novel technique based on reduced order quadratures (ROQs), an application and data-specific quadrature rule, to perform fast and accurate likelihood evaluations. These are the dominant cost in Markov chain Monte Carlo algorithms, which are widely employed in parameter estimation studies, and so ROQs offer a new way to accelerate GW parameter estimation. We illustrate our approach using a four-dimensional GW burst model embedded in noise. We build an ROQ for this model and perform four-dimensional Markov chain Monte Carlo searches with both the standard and ROQ rules, showing that, for this model, the ROQ approach is around 25 times faster than the standard approach with essentially no loss of accuracy. The speed-up from using ROQs is expected to increase for more complex GW signal models and therefore has significant potential to accelerate parameter estimation of GW sources such as compact binary coalescences

Accelerated gravitational wave parameter estimation with reduced order modeling.

This is the author accepted manuscript. The final version is available from APS via http://link.aps.org/doi/10.1103/PhysRevLett.114.071104Inferring the astrophysical parameters of coalescing compact binaries is a key science goal of the upcoming advanced LIGO-Virgo gravitational-wave detector network and, more generally, gravitational-wave astronomy. However, current approaches to parameter estimation for these detectors require computationally expensive algorithms. Therefore, there is a pressing need for new, fast, and accurate Bayesian inference techniques. In this Letter, we demonstrate that a reduced order modeling approach enables rapid parameter estimation to be performed. By implementing a reduced order quadrature scheme within the LIGO Algorithm Library, we show that Bayesian inference on the 9-dimensional parameter space of nonspinning binary neutron star inspirals can be sped up by a factor of ∼30 for the early advanced detectors' configurations (with sensitivities down to around 40 Hz) and ∼70 for sensitivities down to around 20 Hz. This speedup will increase to about 150 as the detectors improve their low-frequency limit to 10 Hz, reducing to hours analyses which could otherwise take months to complete. Although these results focus on interferometric gravitational wave detectors, the techniques are broadly applicable to any experiment where fast Bayesian analysis is desirable.P. C.’s work was supported by a Marie Curie Intra-European Fellowship within the 7th European Community Framework Programme PIEF-GA-2011-299190, FP7-PEOPLE-2011-CIG Grant No. 293412 and STFC Consolidator Grant No. ST/L000636/1. S. E. F. thanks the Institute of Astronomy at Cambridge, UK, where part of this work was done, for hospitality and financial support. J. G.’s work was supported by the Royal Society and V. R. by the LIGO Laboratory and the California Institute of Technology (Caltech). This work was supported in part by NSF Grant No. PHY-1208861 and No. PHY-1316424 to the University of Maryland (UMD), NSF Grant No. PHY-1500818 to the University of California at San Diego, NSF Grants No. PHY-1306125 and No. AST-1333129 to Cornell University, and the Sherman Fairchild Foundation. The authors also gratefully acknowledge the support of the U.S. National Science Foundation for the construction and operation of the LIGO Laboratory under cooperative agreement NSF-PHY-0757058. This paper carries LIGO Document Number LIGO-P1400038. Some of the computations were carried out at the Center for Scientific Computation and Mathematical Modeling cluster at UMD and the LIGO Laboratory computer cluster at Caltech. Portions of this research were conducted with high performance computing resources provided by Louisiana State Universit

Accelerating parameter estimation of gravitational waves from black hole binaries with reduced order quadratures

The inference of binary parameters from gravitational waves (GW) is one of the key science goals of the collaboration operating the advanced ground-based LIGO-Virgo detector network. We employ reduced order quadratures (ROQs) to substantially reduce the size of large inner products arising in Bayesian parameter estimation (PE) and thus enable studies of the GWs emitted by coalescences of spinning stellar mass black hole binaries approaching the full design sensitivity of these detectors. We build the first ROQs that include the inspiral, merger and ringdown parts of the GWs for a single-spin precessing phenomenological waveform model (IMRPhenomP) and for an aligned-spin effective-one-body model (SEOBNRv2). The ROQs for SEOBNRv2 use a separate reduced order model (ROM) as a proxy. The ROQs we have constructed are suitable for any power spectrum density function of ground-based GW detector noise. We find speedups in the calculation of inner products and the likelihood function of up to several hundreds, reducing to days analyses which could otherwise take up to a year to complete